1 2 /* png.c - location for general purpose libpng functions 3 * 4 * Last changed in libpng 1.6.25 [September 1, 2016] 5 * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson 6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) 7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) 8 * 9 * This code is released under the libpng license. 10 * For conditions of distribution and use, see the disclaimer 11 * and license in png.h 12 */ 13 14 #include "pngpriv.h" 15 16 /* Generate a compiler error if there is an old png.h in the search path. */ 17 typedef png_libpng_version_1_6_25 Your_png_h_is_not_version_1_6_25; 18 19 /* Tells libpng that we have already handled the first "num_bytes" bytes 20 * of the PNG file signature. If the PNG data is embedded into another 21 * stream we can set num_bytes = 8 so that libpng will not attempt to read 22 * or write any of the magic bytes before it starts on the IHDR. 23 */ 24 25 #ifdef PNG_READ_SUPPORTED 26 void PNGAPI 27 png_set_sig_bytes(png_structrp png_ptr, int num_bytes) 28 { 29 unsigned int nb = (unsigned int)num_bytes; 30 31 png_debug(1, "in png_set_sig_bytes"); 32 33 if (png_ptr == NULL) 34 return; 35 36 if (num_bytes < 0) 37 nb = 0; 38 39 if (nb > 8) 40 png_error(png_ptr, "Too many bytes for PNG signature"); 41 42 png_ptr->sig_bytes = (png_byte)nb; 43 } 44 45 /* Checks whether the supplied bytes match the PNG signature. We allow 46 * checking less than the full 8-byte signature so that those apps that 47 * already read the first few bytes of a file to determine the file type 48 * can simply check the remaining bytes for extra assurance. Returns 49 * an integer less than, equal to, or greater than zero if sig is found, 50 * respectively, to be less than, to match, or be greater than the correct 51 * PNG signature (this is the same behavior as strcmp, memcmp, etc). 52 */ 53 int PNGAPI 54 png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check) 55 { 56 png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10}; 57 58 if (num_to_check > 8) 59 num_to_check = 8; 60 61 else if (num_to_check < 1) 62 return (-1); 63 64 if (start > 7) 65 return (-1); 66 67 if (start + num_to_check > 8) 68 num_to_check = 8 - start; 69 70 return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check))); 71 } 72 73 #endif /* READ */ 74 75 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) 76 /* Function to allocate memory for zlib */ 77 PNG_FUNCTION(voidpf /* PRIVATE */, 78 png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED) 79 { 80 png_alloc_size_t num_bytes = size; 81 82 if (png_ptr == NULL) 83 return NULL; 84 85 if (items >= (~(png_alloc_size_t)0)/size) 86 { 87 png_warning (png_voidcast(png_structrp, png_ptr), 88 "Potential overflow in png_zalloc()"); 89 return NULL; 90 } 91 92 num_bytes *= items; 93 return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes); 94 } 95 96 /* Function to free memory for zlib */ 97 void /* PRIVATE */ 98 png_zfree(voidpf png_ptr, voidpf ptr) 99 { 100 png_free(png_voidcast(png_const_structrp,png_ptr), ptr); 101 } 102 103 /* Reset the CRC variable to 32 bits of 1's. Care must be taken 104 * in case CRC is > 32 bits to leave the top bits 0. 105 */ 106 void /* PRIVATE */ 107 png_reset_crc(png_structrp png_ptr) 108 { 109 /* The cast is safe because the crc is a 32-bit value. */ 110 png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0); 111 } 112 113 /* Calculate the CRC over a section of data. We can only pass as 114 * much data to this routine as the largest single buffer size. We 115 * also check that this data will actually be used before going to the 116 * trouble of calculating it. 117 */ 118 void /* PRIVATE */ 119 png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length) 120 { 121 int need_crc = 1; 122 123 if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0) 124 { 125 if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) == 126 (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN)) 127 need_crc = 0; 128 } 129 130 else /* critical */ 131 { 132 if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0) 133 need_crc = 0; 134 } 135 136 /* 'uLong' is defined in zlib.h as unsigned long; this means that on some 137 * systems it is a 64-bit value. crc32, however, returns 32 bits so the 138 * following cast is safe. 'uInt' may be no more than 16 bits, so it is 139 * necessary to perform a loop here. 140 */ 141 if (need_crc != 0 && length > 0) 142 { 143 uLong crc = png_ptr->crc; /* Should never issue a warning */ 144 145 do 146 { 147 uInt safe_length = (uInt)length; 148 #ifndef __COVERITY__ 149 if (safe_length == 0) 150 safe_length = (uInt)-1; /* evil, but safe */ 151 #endif 152 153 crc = crc32(crc, ptr, safe_length); 154 155 /* The following should never issue compiler warnings; if they do the 156 * target system has characteristics that will probably violate other 157 * assumptions within the libpng code. 158 */ 159 ptr += safe_length; 160 length -= safe_length; 161 } 162 while (length > 0); 163 164 /* And the following is always safe because the crc is only 32 bits. */ 165 png_ptr->crc = (png_uint_32)crc; 166 } 167 } 168 169 /* Check a user supplied version number, called from both read and write 170 * functions that create a png_struct. 171 */ 172 int 173 png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver) 174 { 175 /* Libpng versions 1.0.0 and later are binary compatible if the version 176 * string matches through the second '.'; we must recompile any 177 * applications that use any older library version. 178 */ 179 180 if (user_png_ver != NULL) 181 { 182 int i = -1; 183 int found_dots = 0; 184 185 do 186 { 187 i++; 188 if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i]) 189 png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH; 190 if (user_png_ver[i] == '.') 191 found_dots++; 192 } while (found_dots < 2 && user_png_ver[i] != 0 && 193 PNG_LIBPNG_VER_STRING[i] != 0); 194 } 195 196 else 197 png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH; 198 199 if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) != 0) 200 { 201 #ifdef PNG_WARNINGS_SUPPORTED 202 size_t pos = 0; 203 char m[128]; 204 205 pos = png_safecat(m, (sizeof m), pos, 206 "Application built with libpng-"); 207 pos = png_safecat(m, (sizeof m), pos, user_png_ver); 208 pos = png_safecat(m, (sizeof m), pos, " but running with "); 209 pos = png_safecat(m, (sizeof m), pos, PNG_LIBPNG_VER_STRING); 210 PNG_UNUSED(pos) 211 212 png_warning(png_ptr, m); 213 #endif 214 215 #ifdef PNG_ERROR_NUMBERS_SUPPORTED 216 png_ptr->flags = 0; 217 #endif 218 219 return 0; 220 } 221 222 /* Success return. */ 223 return 1; 224 } 225 226 /* Generic function to create a png_struct for either read or write - this 227 * contains the common initialization. 228 */ 229 PNG_FUNCTION(png_structp /* PRIVATE */, 230 png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr, 231 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr, 232 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED) 233 { 234 png_struct create_struct; 235 # ifdef PNG_SETJMP_SUPPORTED 236 jmp_buf create_jmp_buf; 237 # endif 238 239 /* This temporary stack-allocated structure is used to provide a place to 240 * build enough context to allow the user provided memory allocator (if any) 241 * to be called. 242 */ 243 memset(&create_struct, 0, (sizeof create_struct)); 244 245 /* Added at libpng-1.2.6 */ 246 # ifdef PNG_USER_LIMITS_SUPPORTED 247 create_struct.user_width_max = PNG_USER_WIDTH_MAX; 248 create_struct.user_height_max = PNG_USER_HEIGHT_MAX; 249 250 # ifdef PNG_USER_CHUNK_CACHE_MAX 251 /* Added at libpng-1.2.43 and 1.4.0 */ 252 create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX; 253 # endif 254 255 # ifdef PNG_USER_CHUNK_MALLOC_MAX 256 /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists 257 * in png_struct regardless. 258 */ 259 create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX; 260 # endif 261 # endif 262 263 /* The following two API calls simply set fields in png_struct, so it is safe 264 * to do them now even though error handling is not yet set up. 265 */ 266 # ifdef PNG_USER_MEM_SUPPORTED 267 png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn); 268 # else 269 PNG_UNUSED(mem_ptr) 270 PNG_UNUSED(malloc_fn) 271 PNG_UNUSED(free_fn) 272 # endif 273 274 /* (*error_fn) can return control to the caller after the error_ptr is set, 275 * this will result in a memory leak unless the error_fn does something 276 * extremely sophisticated. The design lacks merit but is implicit in the 277 * API. 278 */ 279 png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn); 280 281 # ifdef PNG_SETJMP_SUPPORTED 282 if (!setjmp(create_jmp_buf)) 283 # endif 284 { 285 # ifdef PNG_SETJMP_SUPPORTED 286 /* Temporarily fake out the longjmp information until we have 287 * successfully completed this function. This only works if we have 288 * setjmp() support compiled in, but it is safe - this stuff should 289 * never happen. 290 */ 291 create_struct.jmp_buf_ptr = &create_jmp_buf; 292 create_struct.jmp_buf_size = 0; /*stack allocation*/ 293 create_struct.longjmp_fn = longjmp; 294 # endif 295 /* Call the general version checker (shared with read and write code): 296 */ 297 if (png_user_version_check(&create_struct, user_png_ver) != 0) 298 { 299 png_structrp png_ptr = png_voidcast(png_structrp, 300 png_malloc_warn(&create_struct, (sizeof *png_ptr))); 301 302 if (png_ptr != NULL) 303 { 304 /* png_ptr->zstream holds a back-pointer to the png_struct, so 305 * this can only be done now: 306 */ 307 create_struct.zstream.zalloc = png_zalloc; 308 create_struct.zstream.zfree = png_zfree; 309 create_struct.zstream.opaque = png_ptr; 310 311 # ifdef PNG_SETJMP_SUPPORTED 312 /* Eliminate the local error handling: */ 313 create_struct.jmp_buf_ptr = NULL; 314 create_struct.jmp_buf_size = 0; 315 create_struct.longjmp_fn = 0; 316 # endif 317 318 *png_ptr = create_struct; 319 320 /* This is the successful return point */ 321 return png_ptr; 322 } 323 } 324 } 325 326 /* A longjmp because of a bug in the application storage allocator or a 327 * simple failure to allocate the png_struct. 328 */ 329 return NULL; 330 } 331 332 /* Allocate the memory for an info_struct for the application. */ 333 PNG_FUNCTION(png_infop,PNGAPI 334 png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED) 335 { 336 png_inforp info_ptr; 337 338 png_debug(1, "in png_create_info_struct"); 339 340 if (png_ptr == NULL) 341 return NULL; 342 343 /* Use the internal API that does not (or at least should not) error out, so 344 * that this call always returns ok. The application typically sets up the 345 * error handling *after* creating the info_struct because this is the way it 346 * has always been done in 'example.c'. 347 */ 348 info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr, 349 (sizeof *info_ptr))); 350 351 if (info_ptr != NULL) 352 memset(info_ptr, 0, (sizeof *info_ptr)); 353 354 return info_ptr; 355 } 356 357 /* This function frees the memory associated with a single info struct. 358 * Normally, one would use either png_destroy_read_struct() or 359 * png_destroy_write_struct() to free an info struct, but this may be 360 * useful for some applications. From libpng 1.6.0 this function is also used 361 * internally to implement the png_info release part of the 'struct' destroy 362 * APIs. This ensures that all possible approaches free the same data (all of 363 * it). 364 */ 365 void PNGAPI 366 png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr) 367 { 368 png_inforp info_ptr = NULL; 369 370 png_debug(1, "in png_destroy_info_struct"); 371 372 if (png_ptr == NULL) 373 return; 374 375 if (info_ptr_ptr != NULL) 376 info_ptr = *info_ptr_ptr; 377 378 if (info_ptr != NULL) 379 { 380 /* Do this first in case of an error below; if the app implements its own 381 * memory management this can lead to png_free calling png_error, which 382 * will abort this routine and return control to the app error handler. 383 * An infinite loop may result if it then tries to free the same info 384 * ptr. 385 */ 386 *info_ptr_ptr = NULL; 387 388 png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1); 389 memset(info_ptr, 0, (sizeof *info_ptr)); 390 png_free(png_ptr, info_ptr); 391 } 392 } 393 394 /* Initialize the info structure. This is now an internal function (0.89) 395 * and applications using it are urged to use png_create_info_struct() 396 * instead. Use deprecated in 1.6.0, internal use removed (used internally it 397 * is just a memset). 398 * 399 * NOTE: it is almost inconceivable that this API is used because it bypasses 400 * the user-memory mechanism and the user error handling/warning mechanisms in 401 * those cases where it does anything other than a memset. 402 */ 403 PNG_FUNCTION(void,PNGAPI 404 png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size), 405 PNG_DEPRECATED) 406 { 407 png_inforp info_ptr = *ptr_ptr; 408 409 png_debug(1, "in png_info_init_3"); 410 411 if (info_ptr == NULL) 412 return; 413 414 if ((sizeof (png_info)) > png_info_struct_size) 415 { 416 *ptr_ptr = NULL; 417 /* The following line is why this API should not be used: */ 418 free(info_ptr); 419 info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL, 420 (sizeof *info_ptr))); 421 if (info_ptr == NULL) 422 return; 423 *ptr_ptr = info_ptr; 424 } 425 426 /* Set everything to 0 */ 427 memset(info_ptr, 0, (sizeof *info_ptr)); 428 } 429 430 /* The following API is not called internally */ 431 void PNGAPI 432 png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr, 433 int freer, png_uint_32 mask) 434 { 435 png_debug(1, "in png_data_freer"); 436 437 if (png_ptr == NULL || info_ptr == NULL) 438 return; 439 440 if (freer == PNG_DESTROY_WILL_FREE_DATA) 441 info_ptr->free_me |= mask; 442 443 else if (freer == PNG_USER_WILL_FREE_DATA) 444 info_ptr->free_me &= ~mask; 445 446 else 447 png_error(png_ptr, "Unknown freer parameter in png_data_freer"); 448 } 449 450 void PNGAPI 451 png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask, 452 int num) 453 { 454 png_debug(1, "in png_free_data"); 455 456 if (png_ptr == NULL || info_ptr == NULL) 457 return; 458 459 #ifdef PNG_TEXT_SUPPORTED 460 /* Free text item num or (if num == -1) all text items */ 461 if (info_ptr->text != 0 && 462 ((mask & PNG_FREE_TEXT) & info_ptr->free_me) != 0) 463 { 464 if (num != -1) 465 { 466 png_free(png_ptr, info_ptr->text[num].key); 467 info_ptr->text[num].key = NULL; 468 } 469 470 else 471 { 472 int i; 473 474 for (i = 0; i < info_ptr->num_text; i++) 475 png_free(png_ptr, info_ptr->text[i].key); 476 477 png_free(png_ptr, info_ptr->text); 478 info_ptr->text = NULL; 479 info_ptr->num_text = 0; 480 } 481 } 482 #endif 483 484 #ifdef PNG_tRNS_SUPPORTED 485 /* Free any tRNS entry */ 486 if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) != 0) 487 { 488 info_ptr->valid &= ~PNG_INFO_tRNS; 489 png_free(png_ptr, info_ptr->trans_alpha); 490 info_ptr->trans_alpha = NULL; 491 info_ptr->num_trans = 0; 492 } 493 #endif 494 495 #ifdef PNG_sCAL_SUPPORTED 496 /* Free any sCAL entry */ 497 if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) != 0) 498 { 499 png_free(png_ptr, info_ptr->scal_s_width); 500 png_free(png_ptr, info_ptr->scal_s_height); 501 info_ptr->scal_s_width = NULL; 502 info_ptr->scal_s_height = NULL; 503 info_ptr->valid &= ~PNG_INFO_sCAL; 504 } 505 #endif 506 507 #ifdef PNG_pCAL_SUPPORTED 508 /* Free any pCAL entry */ 509 if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) != 0) 510 { 511 png_free(png_ptr, info_ptr->pcal_purpose); 512 png_free(png_ptr, info_ptr->pcal_units); 513 info_ptr->pcal_purpose = NULL; 514 info_ptr->pcal_units = NULL; 515 516 if (info_ptr->pcal_params != NULL) 517 { 518 int i; 519 520 for (i = 0; i < info_ptr->pcal_nparams; i++) 521 png_free(png_ptr, info_ptr->pcal_params[i]); 522 523 png_free(png_ptr, info_ptr->pcal_params); 524 info_ptr->pcal_params = NULL; 525 } 526 info_ptr->valid &= ~PNG_INFO_pCAL; 527 } 528 #endif 529 530 #ifdef PNG_iCCP_SUPPORTED 531 /* Free any profile entry */ 532 if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) != 0) 533 { 534 png_free(png_ptr, info_ptr->iccp_name); 535 png_free(png_ptr, info_ptr->iccp_profile); 536 info_ptr->iccp_name = NULL; 537 info_ptr->iccp_profile = NULL; 538 info_ptr->valid &= ~PNG_INFO_iCCP; 539 } 540 #endif 541 542 #ifdef PNG_sPLT_SUPPORTED 543 /* Free a given sPLT entry, or (if num == -1) all sPLT entries */ 544 if (info_ptr->splt_palettes != 0 && 545 ((mask & PNG_FREE_SPLT) & info_ptr->free_me) != 0) 546 { 547 if (num != -1) 548 { 549 png_free(png_ptr, info_ptr->splt_palettes[num].name); 550 png_free(png_ptr, info_ptr->splt_palettes[num].entries); 551 info_ptr->splt_palettes[num].name = NULL; 552 info_ptr->splt_palettes[num].entries = NULL; 553 } 554 555 else 556 { 557 int i; 558 559 for (i = 0; i < info_ptr->splt_palettes_num; i++) 560 { 561 png_free(png_ptr, info_ptr->splt_palettes[i].name); 562 png_free(png_ptr, info_ptr->splt_palettes[i].entries); 563 } 564 565 png_free(png_ptr, info_ptr->splt_palettes); 566 info_ptr->splt_palettes = NULL; 567 info_ptr->splt_palettes_num = 0; 568 info_ptr->valid &= ~PNG_INFO_sPLT; 569 } 570 } 571 #endif 572 573 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED 574 if (info_ptr->unknown_chunks != 0 && 575 ((mask & PNG_FREE_UNKN) & info_ptr->free_me) != 0) 576 { 577 if (num != -1) 578 { 579 png_free(png_ptr, info_ptr->unknown_chunks[num].data); 580 info_ptr->unknown_chunks[num].data = NULL; 581 } 582 583 else 584 { 585 int i; 586 587 for (i = 0; i < info_ptr->unknown_chunks_num; i++) 588 png_free(png_ptr, info_ptr->unknown_chunks[i].data); 589 590 png_free(png_ptr, info_ptr->unknown_chunks); 591 info_ptr->unknown_chunks = NULL; 592 info_ptr->unknown_chunks_num = 0; 593 } 594 } 595 #endif 596 597 #ifdef PNG_hIST_SUPPORTED 598 /* Free any hIST entry */ 599 if (((mask & PNG_FREE_HIST) & info_ptr->free_me) != 0) 600 { 601 png_free(png_ptr, info_ptr->hist); 602 info_ptr->hist = NULL; 603 info_ptr->valid &= ~PNG_INFO_hIST; 604 } 605 #endif 606 607 /* Free any PLTE entry that was internally allocated */ 608 if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) != 0) 609 { 610 png_free(png_ptr, info_ptr->palette); 611 info_ptr->palette = NULL; 612 info_ptr->valid &= ~PNG_INFO_PLTE; 613 info_ptr->num_palette = 0; 614 } 615 616 #ifdef PNG_INFO_IMAGE_SUPPORTED 617 /* Free any image bits attached to the info structure */ 618 if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) != 0) 619 { 620 if (info_ptr->row_pointers != 0) 621 { 622 png_uint_32 row; 623 for (row = 0; row < info_ptr->height; row++) 624 png_free(png_ptr, info_ptr->row_pointers[row]); 625 626 png_free(png_ptr, info_ptr->row_pointers); 627 info_ptr->row_pointers = NULL; 628 } 629 info_ptr->valid &= ~PNG_INFO_IDAT; 630 } 631 #endif 632 633 if (num != -1) 634 mask &= ~PNG_FREE_MUL; 635 636 info_ptr->free_me &= ~mask; 637 } 638 #endif /* READ || WRITE */ 639 640 /* This function returns a pointer to the io_ptr associated with the user 641 * functions. The application should free any memory associated with this 642 * pointer before png_write_destroy() or png_read_destroy() are called. 643 */ 644 png_voidp PNGAPI 645 png_get_io_ptr(png_const_structrp png_ptr) 646 { 647 if (png_ptr == NULL) 648 return (NULL); 649 650 return (png_ptr->io_ptr); 651 } 652 653 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) 654 # ifdef PNG_STDIO_SUPPORTED 655 /* Initialize the default input/output functions for the PNG file. If you 656 * use your own read or write routines, you can call either png_set_read_fn() 657 * or png_set_write_fn() instead of png_init_io(). If you have defined 658 * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a 659 * function of your own because "FILE *" isn't necessarily available. 660 */ 661 void PNGAPI 662 png_init_io(png_structrp png_ptr, png_FILE_p fp) 663 { 664 png_debug(1, "in png_init_io"); 665 666 if (png_ptr == NULL) 667 return; 668 669 png_ptr->io_ptr = (png_voidp)fp; 670 } 671 # endif 672 673 # ifdef PNG_SAVE_INT_32_SUPPORTED 674 /* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90 675 * defines a cast of a signed integer to an unsigned integer either to preserve 676 * the value, if it is positive, or to calculate: 677 * 678 * (UNSIGNED_MAX+1) + integer 679 * 680 * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the 681 * negative integral value is added the result will be an unsigned value 682 * correspnding to the 2's complement representation. 683 */ 684 void PNGAPI 685 png_save_int_32(png_bytep buf, png_int_32 i) 686 { 687 png_save_uint_32(buf, i); 688 } 689 # endif 690 691 # ifdef PNG_TIME_RFC1123_SUPPORTED 692 /* Convert the supplied time into an RFC 1123 string suitable for use in 693 * a "Creation Time" or other text-based time string. 694 */ 695 int PNGAPI 696 png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime) 697 { 698 static PNG_CONST char short_months[12][4] = 699 {"Jan", "Feb", "Mar", "Apr", "May", "Jun", 700 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; 701 702 if (out == NULL) 703 return 0; 704 705 if (ptime->year > 9999 /* RFC1123 limitation */ || 706 ptime->month == 0 || ptime->month > 12 || 707 ptime->day == 0 || ptime->day > 31 || 708 ptime->hour > 23 || ptime->minute > 59 || 709 ptime->second > 60) 710 return 0; 711 712 { 713 size_t pos = 0; 714 char number_buf[5]; /* enough for a four-digit year */ 715 716 # define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string)) 717 # define APPEND_NUMBER(format, value)\ 718 APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value))) 719 # define APPEND(ch) if (pos < 28) out[pos++] = (ch) 720 721 APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day); 722 APPEND(' '); 723 APPEND_STRING(short_months[(ptime->month - 1)]); 724 APPEND(' '); 725 APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year); 726 APPEND(' '); 727 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour); 728 APPEND(':'); 729 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute); 730 APPEND(':'); 731 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second); 732 APPEND_STRING(" +0000"); /* This reliably terminates the buffer */ 733 PNG_UNUSED (pos) 734 735 # undef APPEND 736 # undef APPEND_NUMBER 737 # undef APPEND_STRING 738 } 739 740 return 1; 741 } 742 743 # if PNG_LIBPNG_VER < 10700 744 /* To do: remove the following from libpng-1.7 */ 745 /* Original API that uses a private buffer in png_struct. 746 * Deprecated because it causes png_struct to carry a spurious temporary 747 * buffer (png_struct::time_buffer), better to have the caller pass this in. 748 */ 749 png_const_charp PNGAPI 750 png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime) 751 { 752 if (png_ptr != NULL) 753 { 754 /* The only failure above if png_ptr != NULL is from an invalid ptime */ 755 if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) == 0) 756 png_warning(png_ptr, "Ignoring invalid time value"); 757 758 else 759 return png_ptr->time_buffer; 760 } 761 762 return NULL; 763 } 764 # endif /* LIBPNG_VER < 10700 */ 765 # endif /* TIME_RFC1123 */ 766 767 #endif /* READ || WRITE */ 768 769 png_const_charp PNGAPI 770 png_get_copyright(png_const_structrp png_ptr) 771 { 772 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ 773 #ifdef PNG_STRING_COPYRIGHT 774 return PNG_STRING_COPYRIGHT 775 #else 776 # ifdef __STDC__ 777 return PNG_STRING_NEWLINE \ 778 "libpng version 1.6.25 - September 1, 2016" PNG_STRING_NEWLINE \ 779 "Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson" \ 780 PNG_STRING_NEWLINE \ 781 "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \ 782 "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \ 783 PNG_STRING_NEWLINE; 784 # else 785 return "libpng version 1.6.25 - September 1, 2016\ 786 Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson\ 787 Copyright (c) 1996-1997 Andreas Dilger\ 788 Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc."; 789 # endif 790 #endif 791 } 792 793 /* The following return the library version as a short string in the 794 * format 1.0.0 through 99.99.99zz. To get the version of *.h files 795 * used with your application, print out PNG_LIBPNG_VER_STRING, which 796 * is defined in png.h. 797 * Note: now there is no difference between png_get_libpng_ver() and 798 * png_get_header_ver(). Due to the version_nn_nn_nn typedef guard, 799 * it is guaranteed that png.c uses the correct version of png.h. 800 */ 801 png_const_charp PNGAPI 802 png_get_libpng_ver(png_const_structrp png_ptr) 803 { 804 /* Version of *.c files used when building libpng */ 805 return png_get_header_ver(png_ptr); 806 } 807 808 png_const_charp PNGAPI 809 png_get_header_ver(png_const_structrp png_ptr) 810 { 811 /* Version of *.h files used when building libpng */ 812 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ 813 return PNG_LIBPNG_VER_STRING; 814 } 815 816 png_const_charp PNGAPI 817 png_get_header_version(png_const_structrp png_ptr) 818 { 819 /* Returns longer string containing both version and date */ 820 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ 821 #ifdef __STDC__ 822 return PNG_HEADER_VERSION_STRING 823 # ifndef PNG_READ_SUPPORTED 824 " (NO READ SUPPORT)" 825 # endif 826 PNG_STRING_NEWLINE; 827 #else 828 return PNG_HEADER_VERSION_STRING; 829 #endif 830 } 831 832 #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED 833 /* NOTE: this routine is not used internally! */ 834 /* Build a grayscale palette. Palette is assumed to be 1 << bit_depth 835 * large of png_color. This lets grayscale images be treated as 836 * paletted. Most useful for gamma correction and simplification 837 * of code. This API is not used internally. 838 */ 839 void PNGAPI 840 png_build_grayscale_palette(int bit_depth, png_colorp palette) 841 { 842 int num_palette; 843 int color_inc; 844 int i; 845 int v; 846 847 png_debug(1, "in png_do_build_grayscale_palette"); 848 849 if (palette == NULL) 850 return; 851 852 switch (bit_depth) 853 { 854 case 1: 855 num_palette = 2; 856 color_inc = 0xff; 857 break; 858 859 case 2: 860 num_palette = 4; 861 color_inc = 0x55; 862 break; 863 864 case 4: 865 num_palette = 16; 866 color_inc = 0x11; 867 break; 868 869 case 8: 870 num_palette = 256; 871 color_inc = 1; 872 break; 873 874 default: 875 num_palette = 0; 876 color_inc = 0; 877 break; 878 } 879 880 for (i = 0, v = 0; i < num_palette; i++, v += color_inc) 881 { 882 palette[i].red = (png_byte)(v & 0xff); 883 palette[i].green = (png_byte)(v & 0xff); 884 palette[i].blue = (png_byte)(v & 0xff); 885 } 886 } 887 #endif 888 889 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED 890 int PNGAPI 891 png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name) 892 { 893 /* Check chunk_name and return "keep" value if it's on the list, else 0 */ 894 png_const_bytep p, p_end; 895 896 if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0) 897 return PNG_HANDLE_CHUNK_AS_DEFAULT; 898 899 p_end = png_ptr->chunk_list; 900 p = p_end + png_ptr->num_chunk_list*5; /* beyond end */ 901 902 /* The code is the fifth byte after each four byte string. Historically this 903 * code was always searched from the end of the list, this is no longer 904 * necessary because the 'set' routine handles duplicate entries correcty. 905 */ 906 do /* num_chunk_list > 0, so at least one */ 907 { 908 p -= 5; 909 910 if (memcmp(chunk_name, p, 4) == 0) 911 return p[4]; 912 } 913 while (p > p_end); 914 915 /* This means that known chunks should be processed and unknown chunks should 916 * be handled according to the value of png_ptr->unknown_default; this can be 917 * confusing because, as a result, there are two levels of defaulting for 918 * unknown chunks. 919 */ 920 return PNG_HANDLE_CHUNK_AS_DEFAULT; 921 } 922 923 #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\ 924 defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED) 925 int /* PRIVATE */ 926 png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name) 927 { 928 png_byte chunk_string[5]; 929 930 PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name); 931 return png_handle_as_unknown(png_ptr, chunk_string); 932 } 933 #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */ 934 #endif /* SET_UNKNOWN_CHUNKS */ 935 936 #ifdef PNG_READ_SUPPORTED 937 /* This function, added to libpng-1.0.6g, is untested. */ 938 int PNGAPI 939 png_reset_zstream(png_structrp png_ptr) 940 { 941 if (png_ptr == NULL) 942 return Z_STREAM_ERROR; 943 944 /* WARNING: this resets the window bits to the maximum! */ 945 return (inflateReset(&png_ptr->zstream)); 946 } 947 #endif /* READ */ 948 949 /* This function was added to libpng-1.0.7 */ 950 png_uint_32 PNGAPI 951 png_access_version_number(void) 952 { 953 /* Version of *.c files used when building libpng */ 954 return((png_uint_32)PNG_LIBPNG_VER); 955 } 956 957 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) 958 /* Ensure that png_ptr->zstream.msg holds some appropriate error message string. 959 * If it doesn't 'ret' is used to set it to something appropriate, even in cases 960 * like Z_OK or Z_STREAM_END where the error code is apparently a success code. 961 */ 962 void /* PRIVATE */ 963 png_zstream_error(png_structrp png_ptr, int ret) 964 { 965 /* Translate 'ret' into an appropriate error string, priority is given to the 966 * one in zstream if set. This always returns a string, even in cases like 967 * Z_OK or Z_STREAM_END where the error code is a success code. 968 */ 969 if (png_ptr->zstream.msg == NULL) switch (ret) 970 { 971 default: 972 case Z_OK: 973 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code"); 974 break; 975 976 case Z_STREAM_END: 977 /* Normal exit */ 978 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream"); 979 break; 980 981 case Z_NEED_DICT: 982 /* This means the deflate stream did not have a dictionary; this 983 * indicates a bogus PNG. 984 */ 985 png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary"); 986 break; 987 988 case Z_ERRNO: 989 /* gz APIs only: should not happen */ 990 png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error"); 991 break; 992 993 case Z_STREAM_ERROR: 994 /* internal libpng error */ 995 png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib"); 996 break; 997 998 case Z_DATA_ERROR: 999 png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream"); 1000 break; 1001 1002 case Z_MEM_ERROR: 1003 png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory"); 1004 break; 1005 1006 case Z_BUF_ERROR: 1007 /* End of input or output; not a problem if the caller is doing 1008 * incremental read or write. 1009 */ 1010 png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated"); 1011 break; 1012 1013 case Z_VERSION_ERROR: 1014 png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version"); 1015 break; 1016 1017 case PNG_UNEXPECTED_ZLIB_RETURN: 1018 /* Compile errors here mean that zlib now uses the value co-opted in 1019 * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above 1020 * and change pngpriv.h. Note that this message is "... return", 1021 * whereas the default/Z_OK one is "... return code". 1022 */ 1023 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return"); 1024 break; 1025 } 1026 } 1027 1028 /* png_convert_size: a PNGAPI but no longer in png.h, so deleted 1029 * at libpng 1.5.5! 1030 */ 1031 1032 /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */ 1033 #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */ 1034 static int 1035 png_colorspace_check_gamma(png_const_structrp png_ptr, 1036 png_colorspacerp colorspace, png_fixed_point gAMA, int from) 1037 /* This is called to check a new gamma value against an existing one. The 1038 * routine returns false if the new gamma value should not be written. 1039 * 1040 * 'from' says where the new gamma value comes from: 1041 * 1042 * 0: the new gamma value is the libpng estimate for an ICC profile 1043 * 1: the new gamma value comes from a gAMA chunk 1044 * 2: the new gamma value comes from an sRGB chunk 1045 */ 1046 { 1047 png_fixed_point gtest; 1048 1049 if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 && 1050 (png_muldiv(>est, colorspace->gamma, PNG_FP_1, gAMA) == 0 || 1051 png_gamma_significant(gtest) != 0)) 1052 { 1053 /* Either this is an sRGB image, in which case the calculated gamma 1054 * approximation should match, or this is an image with a profile and the 1055 * value libpng calculates for the gamma of the profile does not match the 1056 * value recorded in the file. The former, sRGB, case is an error, the 1057 * latter is just a warning. 1058 */ 1059 if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2) 1060 { 1061 png_chunk_report(png_ptr, "gamma value does not match sRGB", 1062 PNG_CHUNK_ERROR); 1063 /* Do not overwrite an sRGB value */ 1064 return from == 2; 1065 } 1066 1067 else /* sRGB tag not involved */ 1068 { 1069 png_chunk_report(png_ptr, "gamma value does not match libpng estimate", 1070 PNG_CHUNK_WARNING); 1071 return from == 1; 1072 } 1073 } 1074 1075 return 1; 1076 } 1077 1078 void /* PRIVATE */ 1079 png_colorspace_set_gamma(png_const_structrp png_ptr, 1080 png_colorspacerp colorspace, png_fixed_point gAMA) 1081 { 1082 /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't 1083 * occur. Since the fixed point representation is asymetrical it is 1084 * possible for 1/gamma to overflow the limit of 21474 and this means the 1085 * gamma value must be at least 5/100000 and hence at most 20000.0. For 1086 * safety the limits here are a little narrower. The values are 0.00016 to 1087 * 6250.0, which are truly ridiculous gamma values (and will produce 1088 * displays that are all black or all white.) 1089 * 1090 * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk 1091 * handling code, which only required the value to be >0. 1092 */ 1093 png_const_charp errmsg; 1094 1095 if (gAMA < 16 || gAMA > 625000000) 1096 errmsg = "gamma value out of range"; 1097 1098 # ifdef PNG_READ_gAMA_SUPPORTED 1099 /* Allow the application to set the gamma value more than once */ 1100 else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 && 1101 (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0) 1102 errmsg = "duplicate"; 1103 # endif 1104 1105 /* Do nothing if the colorspace is already invalid */ 1106 else if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) 1107 return; 1108 1109 else 1110 { 1111 if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1112 1/*from gAMA*/) != 0) 1113 { 1114 /* Store this gamma value. */ 1115 colorspace->gamma = gAMA; 1116 colorspace->flags |= 1117 (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA); 1118 } 1119 1120 /* At present if the check_gamma test fails the gamma of the colorspace is 1121 * not updated however the colorspace is not invalidated. This 1122 * corresponds to the case where the existing gamma comes from an sRGB 1123 * chunk or profile. An error message has already been output. 1124 */ 1125 return; 1126 } 1127 1128 /* Error exit - errmsg has been set. */ 1129 colorspace->flags |= PNG_COLORSPACE_INVALID; 1130 png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR); 1131 } 1132 1133 void /* PRIVATE */ 1134 png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr) 1135 { 1136 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0) 1137 { 1138 /* Everything is invalid */ 1139 info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB| 1140 PNG_INFO_iCCP); 1141 1142 # ifdef PNG_COLORSPACE_SUPPORTED 1143 /* Clean up the iCCP profile now if it won't be used. */ 1144 png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/); 1145 # else 1146 PNG_UNUSED(png_ptr) 1147 # endif 1148 } 1149 1150 else 1151 { 1152 # ifdef PNG_COLORSPACE_SUPPORTED 1153 /* Leave the INFO_iCCP flag set if the pngset.c code has already set 1154 * it; this allows a PNG to contain a profile which matches sRGB and 1155 * yet still have that profile retrievable by the application. 1156 */ 1157 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0) 1158 info_ptr->valid |= PNG_INFO_sRGB; 1159 1160 else 1161 info_ptr->valid &= ~PNG_INFO_sRGB; 1162 1163 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) 1164 info_ptr->valid |= PNG_INFO_cHRM; 1165 1166 else 1167 info_ptr->valid &= ~PNG_INFO_cHRM; 1168 # endif 1169 1170 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0) 1171 info_ptr->valid |= PNG_INFO_gAMA; 1172 1173 else 1174 info_ptr->valid &= ~PNG_INFO_gAMA; 1175 } 1176 } 1177 1178 #ifdef PNG_READ_SUPPORTED 1179 void /* PRIVATE */ 1180 png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr) 1181 { 1182 if (info_ptr == NULL) /* reduce code size; check here not in the caller */ 1183 return; 1184 1185 info_ptr->colorspace = png_ptr->colorspace; 1186 png_colorspace_sync_info(png_ptr, info_ptr); 1187 } 1188 #endif 1189 #endif /* GAMMA */ 1190 1191 #ifdef PNG_COLORSPACE_SUPPORTED 1192 /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for 1193 * cHRM, as opposed to using chromaticities. These internal APIs return 1194 * non-zero on a parameter error. The X, Y and Z values are required to be 1195 * positive and less than 1.0. 1196 */ 1197 static int 1198 png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ) 1199 { 1200 png_int_32 d, dwhite, whiteX, whiteY; 1201 1202 d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z; 1203 if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d) == 0) 1204 return 1; 1205 if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0) 1206 return 1; 1207 dwhite = d; 1208 whiteX = XYZ->red_X; 1209 whiteY = XYZ->red_Y; 1210 1211 d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z; 1212 if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d) == 0) 1213 return 1; 1214 if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0) 1215 return 1; 1216 dwhite += d; 1217 whiteX += XYZ->green_X; 1218 whiteY += XYZ->green_Y; 1219 1220 d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z; 1221 if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d) == 0) 1222 return 1; 1223 if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0) 1224 return 1; 1225 dwhite += d; 1226 whiteX += XYZ->blue_X; 1227 whiteY += XYZ->blue_Y; 1228 1229 /* The reference white is simply the sum of the end-point (X,Y,Z) vectors, 1230 * thus: 1231 */ 1232 if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0) 1233 return 1; 1234 if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0) 1235 return 1; 1236 1237 return 0; 1238 } 1239 1240 static int 1241 png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy) 1242 { 1243 png_fixed_point red_inverse, green_inverse, blue_scale; 1244 png_fixed_point left, right, denominator; 1245 1246 /* Check xy and, implicitly, z. Note that wide gamut color spaces typically 1247 * have end points with 0 tristimulus values (these are impossible end 1248 * points, but they are used to cover the possible colors). We check 1249 * xy->whitey against 5, not 0, to avoid a possible integer overflow. 1250 */ 1251 if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1; 1252 if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1; 1253 if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1; 1254 if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1; 1255 if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1; 1256 if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1; 1257 if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1; 1258 if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1; 1259 1260 /* The reverse calculation is more difficult because the original tristimulus 1261 * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8 1262 * derived values were recorded in the cHRM chunk; 1263 * (red,green,blue,white)x(x,y). This loses one degree of freedom and 1264 * therefore an arbitrary ninth value has to be introduced to undo the 1265 * original transformations. 1266 * 1267 * Think of the original end-points as points in (X,Y,Z) space. The 1268 * chromaticity values (c) have the property: 1269 * 1270 * C 1271 * c = --------- 1272 * X + Y + Z 1273 * 1274 * For each c (x,y,z) from the corresponding original C (X,Y,Z). Thus the 1275 * three chromaticity values (x,y,z) for each end-point obey the 1276 * relationship: 1277 * 1278 * x + y + z = 1 1279 * 1280 * This describes the plane in (X,Y,Z) space that intersects each axis at the 1281 * value 1.0; call this the chromaticity plane. Thus the chromaticity 1282 * calculation has scaled each end-point so that it is on the x+y+z=1 plane 1283 * and chromaticity is the intersection of the vector from the origin to the 1284 * (X,Y,Z) value with the chromaticity plane. 1285 * 1286 * To fully invert the chromaticity calculation we would need the three 1287 * end-point scale factors, (red-scale, green-scale, blue-scale), but these 1288 * were not recorded. Instead we calculated the reference white (X,Y,Z) and 1289 * recorded the chromaticity of this. The reference white (X,Y,Z) would have 1290 * given all three of the scale factors since: 1291 * 1292 * color-C = color-c * color-scale 1293 * white-C = red-C + green-C + blue-C 1294 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale 1295 * 1296 * But cHRM records only white-x and white-y, so we have lost the white scale 1297 * factor: 1298 * 1299 * white-C = white-c*white-scale 1300 * 1301 * To handle this the inverse transformation makes an arbitrary assumption 1302 * about white-scale: 1303 * 1304 * Assume: white-Y = 1.0 1305 * Hence: white-scale = 1/white-y 1306 * Or: red-Y + green-Y + blue-Y = 1.0 1307 * 1308 * Notice the last statement of the assumption gives an equation in three of 1309 * the nine values we want to calculate. 8 more equations come from the 1310 * above routine as summarised at the top above (the chromaticity 1311 * calculation): 1312 * 1313 * Given: color-x = color-X / (color-X + color-Y + color-Z) 1314 * Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0 1315 * 1316 * This is 9 simultaneous equations in the 9 variables "color-C" and can be 1317 * solved by Cramer's rule. Cramer's rule requires calculating 10 9x9 matrix 1318 * determinants, however this is not as bad as it seems because only 28 of 1319 * the total of 90 terms in the various matrices are non-zero. Nevertheless 1320 * Cramer's rule is notoriously numerically unstable because the determinant 1321 * calculation involves the difference of large, but similar, numbers. It is 1322 * difficult to be sure that the calculation is stable for real world values 1323 * and it is certain that it becomes unstable where the end points are close 1324 * together. 1325 * 1326 * So this code uses the perhaps slightly less optimal but more 1327 * understandable and totally obvious approach of calculating color-scale. 1328 * 1329 * This algorithm depends on the precision in white-scale and that is 1330 * (1/white-y), so we can immediately see that as white-y approaches 0 the 1331 * accuracy inherent in the cHRM chunk drops off substantially. 1332 * 1333 * libpng arithmetic: a simple inversion of the above equations 1334 * ------------------------------------------------------------ 1335 * 1336 * white_scale = 1/white-y 1337 * white-X = white-x * white-scale 1338 * white-Y = 1.0 1339 * white-Z = (1 - white-x - white-y) * white_scale 1340 * 1341 * white-C = red-C + green-C + blue-C 1342 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale 1343 * 1344 * This gives us three equations in (red-scale,green-scale,blue-scale) where 1345 * all the coefficients are now known: 1346 * 1347 * red-x*red-scale + green-x*green-scale + blue-x*blue-scale 1348 * = white-x/white-y 1349 * red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1 1350 * red-z*red-scale + green-z*green-scale + blue-z*blue-scale 1351 * = (1 - white-x - white-y)/white-y 1352 * 1353 * In the last equation color-z is (1 - color-x - color-y) so we can add all 1354 * three equations together to get an alternative third: 1355 * 1356 * red-scale + green-scale + blue-scale = 1/white-y = white-scale 1357 * 1358 * So now we have a Cramer's rule solution where the determinants are just 1359 * 3x3 - far more tractible. Unfortunately 3x3 determinants still involve 1360 * multiplication of three coefficients so we can't guarantee to avoid 1361 * overflow in the libpng fixed point representation. Using Cramer's rule in 1362 * floating point is probably a good choice here, but it's not an option for 1363 * fixed point. Instead proceed to simplify the first two equations by 1364 * eliminating what is likely to be the largest value, blue-scale: 1365 * 1366 * blue-scale = white-scale - red-scale - green-scale 1367 * 1368 * Hence: 1369 * 1370 * (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale = 1371 * (white-x - blue-x)*white-scale 1372 * 1373 * (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale = 1374 * 1 - blue-y*white-scale 1375 * 1376 * And now we can trivially solve for (red-scale,green-scale): 1377 * 1378 * green-scale = 1379 * (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale 1380 * ----------------------------------------------------------- 1381 * green-x - blue-x 1382 * 1383 * red-scale = 1384 * 1 - blue-y*white-scale - (green-y - blue-y) * green-scale 1385 * --------------------------------------------------------- 1386 * red-y - blue-y 1387 * 1388 * Hence: 1389 * 1390 * red-scale = 1391 * ( (green-x - blue-x) * (white-y - blue-y) - 1392 * (green-y - blue-y) * (white-x - blue-x) ) / white-y 1393 * ------------------------------------------------------------------------- 1394 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x) 1395 * 1396 * green-scale = 1397 * ( (red-y - blue-y) * (white-x - blue-x) - 1398 * (red-x - blue-x) * (white-y - blue-y) ) / white-y 1399 * ------------------------------------------------------------------------- 1400 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x) 1401 * 1402 * Accuracy: 1403 * The input values have 5 decimal digits of accuracy. The values are all in 1404 * the range 0 < value < 1, so simple products are in the same range but may 1405 * need up to 10 decimal digits to preserve the original precision and avoid 1406 * underflow. Because we are using a 32-bit signed representation we cannot 1407 * match this; the best is a little over 9 decimal digits, less than 10. 1408 * 1409 * The approach used here is to preserve the maximum precision within the 1410 * signed representation. Because the red-scale calculation above uses the 1411 * difference between two products of values that must be in the range -1..+1 1412 * it is sufficient to divide the product by 7; ceil(100,000/32767*2). The 1413 * factor is irrelevant in the calculation because it is applied to both 1414 * numerator and denominator. 1415 * 1416 * Note that the values of the differences of the products of the 1417 * chromaticities in the above equations tend to be small, for example for 1418 * the sRGB chromaticities they are: 1419 * 1420 * red numerator: -0.04751 1421 * green numerator: -0.08788 1422 * denominator: -0.2241 (without white-y multiplication) 1423 * 1424 * The resultant Y coefficients from the chromaticities of some widely used 1425 * color space definitions are (to 15 decimal places): 1426 * 1427 * sRGB 1428 * 0.212639005871510 0.715168678767756 0.072192315360734 1429 * Kodak ProPhoto 1430 * 0.288071128229293 0.711843217810102 0.000085653960605 1431 * Adobe RGB 1432 * 0.297344975250536 0.627363566255466 0.075291458493998 1433 * Adobe Wide Gamut RGB 1434 * 0.258728243040113 0.724682314948566 0.016589442011321 1435 */ 1436 /* By the argument, above overflow should be impossible here. The return 1437 * value of 2 indicates an internal error to the caller. 1438 */ 1439 if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7) == 0) 1440 return 2; 1441 if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7) == 0) 1442 return 2; 1443 denominator = left - right; 1444 1445 /* Now find the red numerator. */ 1446 if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7) == 0) 1447 return 2; 1448 if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7) == 0) 1449 return 2; 1450 1451 /* Overflow is possible here and it indicates an extreme set of PNG cHRM 1452 * chunk values. This calculation actually returns the reciprocal of the 1453 * scale value because this allows us to delay the multiplication of white-y 1454 * into the denominator, which tends to produce a small number. 1455 */ 1456 if (png_muldiv(&red_inverse, xy->whitey, denominator, left-right) == 0 || 1457 red_inverse <= xy->whitey /* r+g+b scales = white scale */) 1458 return 1; 1459 1460 /* Similarly for green_inverse: */ 1461 if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7) == 0) 1462 return 2; 1463 if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7) == 0) 1464 return 2; 1465 if (png_muldiv(&green_inverse, xy->whitey, denominator, left-right) == 0 || 1466 green_inverse <= xy->whitey) 1467 return 1; 1468 1469 /* And the blue scale, the checks above guarantee this can't overflow but it 1470 * can still produce 0 for extreme cHRM values. 1471 */ 1472 blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) - 1473 png_reciprocal(green_inverse); 1474 if (blue_scale <= 0) 1475 return 1; 1476 1477 1478 /* And fill in the png_XYZ: */ 1479 if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) == 0) 1480 return 1; 1481 if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0) 1482 return 1; 1483 if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1, 1484 red_inverse) == 0) 1485 return 1; 1486 1487 if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0) 1488 return 1; 1489 if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0) 1490 return 1; 1491 if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1, 1492 green_inverse) == 0) 1493 return 1; 1494 1495 if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0) 1496 return 1; 1497 if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0) 1498 return 1; 1499 if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale, 1500 PNG_FP_1) == 0) 1501 return 1; 1502 1503 return 0; /*success*/ 1504 } 1505 1506 static int 1507 png_XYZ_normalize(png_XYZ *XYZ) 1508 { 1509 png_int_32 Y; 1510 1511 if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 || 1512 XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 || 1513 XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0) 1514 return 1; 1515 1516 /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1. 1517 * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore 1518 * relying on addition of two positive values producing a negative one is not 1519 * safe. 1520 */ 1521 Y = XYZ->red_Y; 1522 if (0x7fffffff - Y < XYZ->green_X) 1523 return 1; 1524 Y += XYZ->green_Y; 1525 if (0x7fffffff - Y < XYZ->blue_X) 1526 return 1; 1527 Y += XYZ->blue_Y; 1528 1529 if (Y != PNG_FP_1) 1530 { 1531 if (png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y) == 0) 1532 return 1; 1533 if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0) 1534 return 1; 1535 if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0) 1536 return 1; 1537 1538 if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0) 1539 return 1; 1540 if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0) 1541 return 1; 1542 if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0) 1543 return 1; 1544 1545 if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0) 1546 return 1; 1547 if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0) 1548 return 1; 1549 if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0) 1550 return 1; 1551 } 1552 1553 return 0; 1554 } 1555 1556 static int 1557 png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta) 1558 { 1559 /* Allow an error of +/-0.01 (absolute value) on each chromaticity */ 1560 if (PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) || 1561 PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) || 1562 PNG_OUT_OF_RANGE(xy1->redx, xy2->redx, delta) || 1563 PNG_OUT_OF_RANGE(xy1->redy, xy2->redy, delta) || 1564 PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) || 1565 PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) || 1566 PNG_OUT_OF_RANGE(xy1->bluex, xy2->bluex, delta) || 1567 PNG_OUT_OF_RANGE(xy1->bluey, xy2->bluey, delta)) 1568 return 0; 1569 return 1; 1570 } 1571 1572 /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM 1573 * chunk chromaticities. Earlier checks used to simply look for the overflow 1574 * condition (where the determinant of the matrix to solve for XYZ ends up zero 1575 * because the chromaticity values are not all distinct.) Despite this it is 1576 * theoretically possible to produce chromaticities that are apparently valid 1577 * but that rapidly degrade to invalid, potentially crashing, sets because of 1578 * arithmetic inaccuracies when calculations are performed on them. The new 1579 * check is to round-trip xy -> XYZ -> xy and then check that the result is 1580 * within a small percentage of the original. 1581 */ 1582 static int 1583 png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy) 1584 { 1585 int result; 1586 png_xy xy_test; 1587 1588 /* As a side-effect this routine also returns the XYZ endpoints. */ 1589 result = png_XYZ_from_xy(XYZ, xy); 1590 if (result != 0) 1591 return result; 1592 1593 result = png_xy_from_XYZ(&xy_test, XYZ); 1594 if (result != 0) 1595 return result; 1596 1597 if (png_colorspace_endpoints_match(xy, &xy_test, 1598 5/*actually, the math is pretty accurate*/) != 0) 1599 return 0; 1600 1601 /* Too much slip */ 1602 return 1; 1603 } 1604 1605 /* This is the check going the other way. The XYZ is modified to normalize it 1606 * (another side-effect) and the xy chromaticities are returned. 1607 */ 1608 static int 1609 png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ) 1610 { 1611 int result; 1612 png_XYZ XYZtemp; 1613 1614 result = png_XYZ_normalize(XYZ); 1615 if (result != 0) 1616 return result; 1617 1618 result = png_xy_from_XYZ(xy, XYZ); 1619 if (result != 0) 1620 return result; 1621 1622 XYZtemp = *XYZ; 1623 return png_colorspace_check_xy(&XYZtemp, xy); 1624 } 1625 1626 /* Used to check for an endpoint match against sRGB */ 1627 static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */ 1628 { 1629 /* color x y */ 1630 /* red */ 64000, 33000, 1631 /* green */ 30000, 60000, 1632 /* blue */ 15000, 6000, 1633 /* white */ 31270, 32900 1634 }; 1635 1636 static int 1637 png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr, 1638 png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ, 1639 int preferred) 1640 { 1641 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) 1642 return 0; 1643 1644 /* The consistency check is performed on the chromaticities; this factors out 1645 * variations because of the normalization (or not) of the end point Y 1646 * values. 1647 */ 1648 if (preferred < 2 && 1649 (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) 1650 { 1651 /* The end points must be reasonably close to any we already have. The 1652 * following allows an error of up to +/-.001 1653 */ 1654 if (png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 1655 100) == 0) 1656 { 1657 colorspace->flags |= PNG_COLORSPACE_INVALID; 1658 png_benign_error(png_ptr, "inconsistent chromaticities"); 1659 return 0; /* failed */ 1660 } 1661 1662 /* Only overwrite with preferred values */ 1663 if (preferred == 0) 1664 return 1; /* ok, but no change */ 1665 } 1666 1667 colorspace->end_points_xy = *xy; 1668 colorspace->end_points_XYZ = *XYZ; 1669 colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS; 1670 1671 /* The end points are normally quoted to two decimal digits, so allow +/-0.01 1672 * on this test. 1673 */ 1674 if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000) != 0) 1675 colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB; 1676 1677 else 1678 colorspace->flags &= PNG_COLORSPACE_CANCEL( 1679 PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB); 1680 1681 return 2; /* ok and changed */ 1682 } 1683 1684 int /* PRIVATE */ 1685 png_colorspace_set_chromaticities(png_const_structrp png_ptr, 1686 png_colorspacerp colorspace, const png_xy *xy, int preferred) 1687 { 1688 /* We must check the end points to ensure they are reasonable - in the past 1689 * color management systems have crashed as a result of getting bogus 1690 * colorant values, while this isn't the fault of libpng it is the 1691 * responsibility of libpng because PNG carries the bomb and libpng is in a 1692 * position to protect against it. 1693 */ 1694 png_XYZ XYZ; 1695 1696 switch (png_colorspace_check_xy(&XYZ, xy)) 1697 { 1698 case 0: /* success */ 1699 return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ, 1700 preferred); 1701 1702 case 1: 1703 /* We can't invert the chromaticities so we can't produce value XYZ 1704 * values. Likely as not a color management system will fail too. 1705 */ 1706 colorspace->flags |= PNG_COLORSPACE_INVALID; 1707 png_benign_error(png_ptr, "invalid chromaticities"); 1708 break; 1709 1710 default: 1711 /* libpng is broken; this should be a warning but if it happens we 1712 * want error reports so for the moment it is an error. 1713 */ 1714 colorspace->flags |= PNG_COLORSPACE_INVALID; 1715 png_error(png_ptr, "internal error checking chromaticities"); 1716 } 1717 1718 return 0; /* failed */ 1719 } 1720 1721 int /* PRIVATE */ 1722 png_colorspace_set_endpoints(png_const_structrp png_ptr, 1723 png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred) 1724 { 1725 png_XYZ XYZ = *XYZ_in; 1726 png_xy xy; 1727 1728 switch (png_colorspace_check_XYZ(&xy, &XYZ)) 1729 { 1730 case 0: 1731 return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ, 1732 preferred); 1733 1734 case 1: 1735 /* End points are invalid. */ 1736 colorspace->flags |= PNG_COLORSPACE_INVALID; 1737 png_benign_error(png_ptr, "invalid end points"); 1738 break; 1739 1740 default: 1741 colorspace->flags |= PNG_COLORSPACE_INVALID; 1742 png_error(png_ptr, "internal error checking chromaticities"); 1743 } 1744 1745 return 0; /* failed */ 1746 } 1747 1748 #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED) 1749 /* Error message generation */ 1750 static char 1751 png_icc_tag_char(png_uint_32 byte) 1752 { 1753 byte &= 0xff; 1754 if (byte >= 32 && byte <= 126) 1755 return (char)byte; 1756 else 1757 return '?'; 1758 } 1759 1760 static void 1761 png_icc_tag_name(char *name, png_uint_32 tag) 1762 { 1763 name[0] = '\''; 1764 name[1] = png_icc_tag_char(tag >> 24); 1765 name[2] = png_icc_tag_char(tag >> 16); 1766 name[3] = png_icc_tag_char(tag >> 8); 1767 name[4] = png_icc_tag_char(tag ); 1768 name[5] = '\''; 1769 } 1770 1771 static int 1772 is_ICC_signature_char(png_alloc_size_t it) 1773 { 1774 return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) || 1775 (it >= 97 && it <= 122); 1776 } 1777 1778 static int 1779 is_ICC_signature(png_alloc_size_t it) 1780 { 1781 return is_ICC_signature_char(it >> 24) /* checks all the top bits */ && 1782 is_ICC_signature_char((it >> 16) & 0xff) && 1783 is_ICC_signature_char((it >> 8) & 0xff) && 1784 is_ICC_signature_char(it & 0xff); 1785 } 1786 1787 static int 1788 png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace, 1789 png_const_charp name, png_alloc_size_t value, png_const_charp reason) 1790 { 1791 size_t pos; 1792 char message[196]; /* see below for calculation */ 1793 1794 if (colorspace != NULL) 1795 colorspace->flags |= PNG_COLORSPACE_INVALID; 1796 1797 pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */ 1798 pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */ 1799 pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */ 1800 if (is_ICC_signature(value) != 0) 1801 { 1802 /* So 'value' is at most 4 bytes and the following cast is safe */ 1803 png_icc_tag_name(message+pos, (png_uint_32)value); 1804 pos += 6; /* total +8; less than the else clause */ 1805 message[pos++] = ':'; 1806 message[pos++] = ' '; 1807 } 1808 # ifdef PNG_WARNINGS_SUPPORTED 1809 else 1810 { 1811 char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/ 1812 1813 pos = png_safecat(message, (sizeof message), pos, 1814 png_format_number(number, number+(sizeof number), 1815 PNG_NUMBER_FORMAT_x, value)); 1816 pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/ 1817 } 1818 # endif 1819 /* The 'reason' is an arbitrary message, allow +79 maximum 195 */ 1820 pos = png_safecat(message, (sizeof message), pos, reason); 1821 PNG_UNUSED(pos) 1822 1823 /* This is recoverable, but make it unconditionally an app_error on write to 1824 * avoid writing invalid ICC profiles into PNG files (i.e., we handle them 1825 * on read, with a warning, but on write unless the app turns off 1826 * application errors the PNG won't be written.) 1827 */ 1828 png_chunk_report(png_ptr, message, 1829 (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR); 1830 1831 return 0; 1832 } 1833 #endif /* sRGB || iCCP */ 1834 1835 #ifdef PNG_sRGB_SUPPORTED 1836 int /* PRIVATE */ 1837 png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace, 1838 int intent) 1839 { 1840 /* sRGB sets known gamma, end points and (from the chunk) intent. */ 1841 /* IMPORTANT: these are not necessarily the values found in an ICC profile 1842 * because ICC profiles store values adapted to a D50 environment; it is 1843 * expected that the ICC profile mediaWhitePointTag will be D50; see the 1844 * checks and code elsewhere to understand this better. 1845 * 1846 * These XYZ values, which are accurate to 5dp, produce rgb to gray 1847 * coefficients of (6968,23435,2366), which are reduced (because they add up 1848 * to 32769 not 32768) to (6968,23434,2366). These are the values that 1849 * libpng has traditionally used (and are the best values given the 15bit 1850 * algorithm used by the rgb to gray code.) 1851 */ 1852 static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */ 1853 { 1854 /* color X Y Z */ 1855 /* red */ 41239, 21264, 1933, 1856 /* green */ 35758, 71517, 11919, 1857 /* blue */ 18048, 7219, 95053 1858 }; 1859 1860 /* Do nothing if the colorspace is already invalidated. */ 1861 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) 1862 return 0; 1863 1864 /* Check the intent, then check for existing settings. It is valid for the 1865 * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must 1866 * be consistent with the correct values. If, however, this function is 1867 * called below because an iCCP chunk matches sRGB then it is quite 1868 * conceivable that an older app recorded incorrect gAMA and cHRM because of 1869 * an incorrect calculation based on the values in the profile - this does 1870 * *not* invalidate the profile (though it still produces an error, which can 1871 * be ignored.) 1872 */ 1873 if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST) 1874 return png_icc_profile_error(png_ptr, colorspace, "sRGB", 1875 (unsigned)intent, "invalid sRGB rendering intent"); 1876 1877 if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 && 1878 colorspace->rendering_intent != intent) 1879 return png_icc_profile_error(png_ptr, colorspace, "sRGB", 1880 (unsigned)intent, "inconsistent rendering intents"); 1881 1882 if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0) 1883 { 1884 png_benign_error(png_ptr, "duplicate sRGB information ignored"); 1885 return 0; 1886 } 1887 1888 /* If the standard sRGB cHRM chunk does not match the one from the PNG file 1889 * warn but overwrite the value with the correct one. 1890 */ 1891 if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 && 1892 !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy, 1893 100)) 1894 png_chunk_report(png_ptr, "cHRM chunk does not match sRGB", 1895 PNG_CHUNK_ERROR); 1896 1897 /* This check is just done for the error reporting - the routine always 1898 * returns true when the 'from' argument corresponds to sRGB (2). 1899 */ 1900 (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE, 1901 2/*from sRGB*/); 1902 1903 /* intent: bugs in GCC force 'int' to be used as the parameter type. */ 1904 colorspace->rendering_intent = (png_uint_16)intent; 1905 colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT; 1906 1907 /* endpoints */ 1908 colorspace->end_points_xy = sRGB_xy; 1909 colorspace->end_points_XYZ = sRGB_XYZ; 1910 colorspace->flags |= 1911 (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB); 1912 1913 /* gamma */ 1914 colorspace->gamma = PNG_GAMMA_sRGB_INVERSE; 1915 colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA; 1916 1917 /* Finally record that we have an sRGB profile */ 1918 colorspace->flags |= 1919 (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB); 1920 1921 return 1; /* set */ 1922 } 1923 #endif /* sRGB */ 1924 1925 #ifdef PNG_iCCP_SUPPORTED 1926 /* Encoded value of D50 as an ICC XYZNumber. From the ICC 2010 spec the value 1927 * is XYZ(0.9642,1.0,0.8249), which scales to: 1928 * 1929 * (63189.8112, 65536, 54060.6464) 1930 */ 1931 static const png_byte D50_nCIEXYZ[12] = 1932 { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d }; 1933 1934 static int /* bool */ 1935 icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace, 1936 png_const_charp name, png_uint_32 profile_length) 1937 { 1938 if (profile_length < 132) 1939 return png_icc_profile_error(png_ptr, colorspace, name, profile_length, 1940 "too short"); 1941 1942 return 1; 1943 } 1944 1945 #ifdef PNG_READ_iCCP_SUPPORTED 1946 int /* PRIVATE */ 1947 png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace, 1948 png_const_charp name, png_uint_32 profile_length) 1949 { 1950 if (!icc_check_length(png_ptr, colorspace, name, profile_length)) 1951 return 0; 1952 1953 /* This needs to be here because the 'normal' check is in 1954 * png_decompress_chunk, yet this happens after the attempt to 1955 * png_malloc_base the required data. We only need this on read; on write 1956 * the caller supplies the profile buffer so libpng doesn't allocate it. See 1957 * the call to icc_check_length below (the write case). 1958 */ 1959 # ifdef PNG_SET_USER_LIMITS_SUPPORTED 1960 else if (png_ptr->user_chunk_malloc_max > 0 && 1961 png_ptr->user_chunk_malloc_max < profile_length) 1962 return png_icc_profile_error(png_ptr, colorspace, name, profile_length, 1963 "exceeds application limits"); 1964 # elif PNG_USER_CHUNK_MALLOC_MAX > 0 1965 else if (PNG_USER_CHUNK_MALLOC_MAX < profile_length) 1966 return png_icc_profile_error(png_ptr, colorspace, name, profile_length, 1967 "exceeds libpng limits"); 1968 # else /* !SET_USER_LIMITS */ 1969 /* This will get compiled out on all 32-bit and better systems. */ 1970 else if (PNG_SIZE_MAX < profile_length) 1971 return png_icc_profile_error(png_ptr, colorspace, name, profile_length, 1972 "exceeds system limits"); 1973 # endif /* !SET_USER_LIMITS */ 1974 1975 return 1; 1976 } 1977 #endif /* READ_iCCP */ 1978 1979 int /* PRIVATE */ 1980 png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace, 1981 png_const_charp name, png_uint_32 profile_length, 1982 png_const_bytep profile/* first 132 bytes only */, int color_type) 1983 { 1984 png_uint_32 temp; 1985 1986 /* Length check; this cannot be ignored in this code because profile_length 1987 * is used later to check the tag table, so even if the profile seems over 1988 * long profile_length from the caller must be correct. The caller can fix 1989 * this up on read or write by just passing in the profile header length. 1990 */ 1991 temp = png_get_uint_32(profile); 1992 if (temp != profile_length) 1993 return png_icc_profile_error(png_ptr, colorspace, name, temp, 1994 "length does not match profile"); 1995 1996 temp = (png_uint_32) (*(profile+8)); 1997 if (temp > 3 && (profile_length & 3)) 1998 return png_icc_profile_error(png_ptr, colorspace, name, profile_length, 1999 "invalid length"); 2000 2001 temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */ 2002 if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */ 2003 profile_length < 132+12*temp) /* truncated tag table */ 2004 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2005 "tag count too large"); 2006 2007 /* The 'intent' must be valid or we can't store it, ICC limits the intent to 2008 * 16 bits. 2009 */ 2010 temp = png_get_uint_32(profile+64); 2011 if (temp >= 0xffff) /* The ICC limit */ 2012 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2013 "invalid rendering intent"); 2014 2015 /* This is just a warning because the profile may be valid in future 2016 * versions. 2017 */ 2018 if (temp >= PNG_sRGB_INTENT_LAST) 2019 (void)png_icc_profile_error(png_ptr, NULL, name, temp, 2020 "intent outside defined range"); 2021 2022 /* At this point the tag table can't be checked because it hasn't necessarily 2023 * been loaded; however, various header fields can be checked. These checks 2024 * are for values permitted by the PNG spec in an ICC profile; the PNG spec 2025 * restricts the profiles that can be passed in an iCCP chunk (they must be 2026 * appropriate to processing PNG data!) 2027 */ 2028 2029 /* Data checks (could be skipped). These checks must be independent of the 2030 * version number; however, the version number doesn't accomodate changes in 2031 * the header fields (just the known tags and the interpretation of the 2032 * data.) 2033 */ 2034 temp = png_get_uint_32(profile+36); /* signature 'ascp' */ 2035 if (temp != 0x61637370) 2036 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2037 "invalid signature"); 2038 2039 /* Currently the PCS illuminant/adopted white point (the computational 2040 * white point) are required to be D50, 2041 * however the profile contains a record of the illuminant so perhaps ICC 2042 * expects to be able to change this in the future (despite the rationale in 2043 * the introduction for using a fixed PCS adopted white.) Consequently the 2044 * following is just a warning. 2045 */ 2046 if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0) 2047 (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/, 2048 "PCS illuminant is not D50"); 2049 2050 /* The PNG spec requires this: 2051 * "If the iCCP chunk is present, the image samples conform to the colour 2052 * space represented by the embedded ICC profile as defined by the 2053 * International Color Consortium [ICC]. The colour space of the ICC profile 2054 * shall be an RGB colour space for colour images (PNG colour types 2, 3, and 2055 * 6), or a greyscale colour space for greyscale images (PNG colour types 0 2056 * and 4)." 2057 * 2058 * This checking code ensures the embedded profile (on either read or write) 2059 * conforms to the specification requirements. Notice that an ICC 'gray' 2060 * color-space profile contains the information to transform the monochrome 2061 * data to XYZ or L*a*b (according to which PCS the profile uses) and this 2062 * should be used in preference to the standard libpng K channel replication 2063 * into R, G and B channels. 2064 * 2065 * Previously it was suggested that an RGB profile on grayscale data could be 2066 * handled. However it it is clear that using an RGB profile in this context 2067 * must be an error - there is no specification of what it means. Thus it is 2068 * almost certainly more correct to ignore the profile. 2069 */ 2070 temp = png_get_uint_32(profile+16); /* data colour space field */ 2071 switch (temp) 2072 { 2073 case 0x52474220: /* 'RGB ' */ 2074 if ((color_type & PNG_COLOR_MASK_COLOR) == 0) 2075 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2076 "RGB color space not permitted on grayscale PNG"); 2077 break; 2078 2079 case 0x47524159: /* 'GRAY' */ 2080 if ((color_type & PNG_COLOR_MASK_COLOR) != 0) 2081 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2082 "Gray color space not permitted on RGB PNG"); 2083 break; 2084 2085 default: 2086 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2087 "invalid ICC profile color space"); 2088 } 2089 2090 /* It is up to the application to check that the profile class matches the 2091 * application requirements; the spec provides no guidance, but it's pretty 2092 * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer 2093 * ('prtr') or 'spac' (for generic color spaces). Issue a warning in these 2094 * cases. Issue an error for device link or abstract profiles - these don't 2095 * contain the records necessary to transform the color-space to anything 2096 * other than the target device (and not even that for an abstract profile). 2097 * Profiles of these classes may not be embedded in images. 2098 */ 2099 temp = png_get_uint_32(profile+12); /* profile/device class */ 2100 switch (temp) 2101 { 2102 case 0x73636e72: /* 'scnr' */ 2103 case 0x6d6e7472: /* 'mntr' */ 2104 case 0x70727472: /* 'prtr' */ 2105 case 0x73706163: /* 'spac' */ 2106 /* All supported */ 2107 break; 2108 2109 case 0x61627374: /* 'abst' */ 2110 /* May not be embedded in an image */ 2111 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2112 "invalid embedded Abstract ICC profile"); 2113 2114 case 0x6c696e6b: /* 'link' */ 2115 /* DeviceLink profiles cannot be interpreted in a non-device specific 2116 * fashion, if an app uses the AToB0Tag in the profile the results are 2117 * undefined unless the result is sent to the intended device, 2118 * therefore a DeviceLink profile should not be found embedded in a 2119 * PNG. 2120 */ 2121 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2122 "unexpected DeviceLink ICC profile class"); 2123 2124 case 0x6e6d636c: /* 'nmcl' */ 2125 /* A NamedColor profile is also device specific, however it doesn't 2126 * contain an AToB0 tag that is open to misinterpretation. Almost 2127 * certainly it will fail the tests below. 2128 */ 2129 (void)png_icc_profile_error(png_ptr, NULL, name, temp, 2130 "unexpected NamedColor ICC profile class"); 2131 break; 2132 2133 default: 2134 /* To allow for future enhancements to the profile accept unrecognized 2135 * profile classes with a warning, these then hit the test below on the 2136 * tag content to ensure they are backward compatible with one of the 2137 * understood profiles. 2138 */ 2139 (void)png_icc_profile_error(png_ptr, NULL, name, temp, 2140 "unrecognized ICC profile class"); 2141 break; 2142 } 2143 2144 /* For any profile other than a device link one the PCS must be encoded 2145 * either in XYZ or Lab. 2146 */ 2147 temp = png_get_uint_32(profile+20); 2148 switch (temp) 2149 { 2150 case 0x58595a20: /* 'XYZ ' */ 2151 case 0x4c616220: /* 'Lab ' */ 2152 break; 2153 2154 default: 2155 return png_icc_profile_error(png_ptr, colorspace, name, temp, 2156 "unexpected ICC PCS encoding"); 2157 } 2158 2159 return 1; 2160 } 2161 2162 int /* PRIVATE */ 2163 png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace, 2164 png_const_charp name, png_uint_32 profile_length, 2165 png_const_bytep profile /* header plus whole tag table */) 2166 { 2167 png_uint_32 tag_count = png_get_uint_32(profile+128); 2168 png_uint_32 itag; 2169 png_const_bytep tag = profile+132; /* The first tag */ 2170 2171 /* First scan all the tags in the table and add bits to the icc_info value 2172 * (temporarily in 'tags'). 2173 */ 2174 for (itag=0; itag < tag_count; ++itag, tag += 12) 2175 { 2176 png_uint_32 tag_id = png_get_uint_32(tag+0); 2177 png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */ 2178 png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */ 2179 2180 /* The ICC specification does not exclude zero length tags, therefore the 2181 * start might actually be anywhere if there is no data, but this would be 2182 * a clear abuse of the intent of the standard so the start is checked for 2183 * being in range. All defined tag types have an 8 byte header - a 4 byte 2184 * type signature then 0. 2185 */ 2186 if ((tag_start & 3) != 0) 2187 { 2188 /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is 2189 * only a warning here because libpng does not care about the 2190 * alignment. 2191 */ 2192 (void)png_icc_profile_error(png_ptr, NULL, name, tag_id, 2193 "ICC profile tag start not a multiple of 4"); 2194 } 2195 2196 /* This is a hard error; potentially it can cause read outside the 2197 * profile. 2198 */ 2199 if (tag_start > profile_length || tag_length > profile_length - tag_start) 2200 return png_icc_profile_error(png_ptr, colorspace, name, tag_id, 2201 "ICC profile tag outside profile"); 2202 } 2203 2204 return 1; /* success, maybe with warnings */ 2205 } 2206 2207 #ifdef PNG_sRGB_SUPPORTED 2208 #if PNG_sRGB_PROFILE_CHECKS >= 0 2209 /* Information about the known ICC sRGB profiles */ 2210 static const struct 2211 { 2212 png_uint_32 adler, crc, length; 2213 png_uint_32 md5[4]; 2214 png_byte have_md5; 2215 png_byte is_broken; 2216 png_uint_16 intent; 2217 2218 # define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0) 2219 # define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\ 2220 { adler, crc, length, md5, broke, intent }, 2221 2222 } png_sRGB_checks[] = 2223 { 2224 /* This data comes from contrib/tools/checksum-icc run on downloads of 2225 * all four ICC sRGB profiles from www.color.org. 2226 */ 2227 /* adler32, crc32, MD5[4], intent, date, length, file-name */ 2228 PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9, 2229 PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0, 2230 "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc") 2231 2232 /* ICC sRGB v2 perceptual no black-compensation: */ 2233 PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21, 2234 PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0, 2235 "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc") 2236 2237 PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae, 2238 PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0, 2239 "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc") 2240 2241 /* ICC sRGB v4 perceptual */ 2242 PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812, 2243 PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0, 2244 "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc") 2245 2246 /* The following profiles have no known MD5 checksum. If there is a match 2247 * on the (empty) MD5 the other fields are used to attempt a match and 2248 * a warning is produced. The first two of these profiles have a 'cprt' tag 2249 * which suggests that they were also made by Hewlett Packard. 2250 */ 2251 PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce, 2252 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0, 2253 "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc") 2254 2255 /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not 2256 * match the D50 PCS illuminant in the header (it is in fact the D65 values, 2257 * so the white point is recorded as the un-adapted value.) The profiles 2258 * below only differ in one byte - the intent - and are basically the same as 2259 * the previous profile except for the mediaWhitePointTag error and a missing 2260 * chromaticAdaptationTag. 2261 */ 2262 PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552, 2263 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/, 2264 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual") 2265 2266 PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d, 2267 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/, 2268 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative") 2269 }; 2270 2271 static int 2272 png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr, 2273 png_const_bytep profile, uLong adler) 2274 { 2275 /* The quick check is to verify just the MD5 signature and trust the 2276 * rest of the data. Because the profile has already been verified for 2277 * correctness this is safe. png_colorspace_set_sRGB will check the 'intent' 2278 * field too, so if the profile has been edited with an intent not defined 2279 * by sRGB (but maybe defined by a later ICC specification) the read of 2280 * the profile will fail at that point. 2281 */ 2282 2283 png_uint_32 length = 0; 2284 png_uint_32 intent = 0x10000; /* invalid */ 2285 #if PNG_sRGB_PROFILE_CHECKS > 1 2286 uLong crc = 0; /* the value for 0 length data */ 2287 #endif 2288 unsigned int i; 2289 2290 #ifdef PNG_SET_OPTION_SUPPORTED 2291 /* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */ 2292 if (((png_ptr->options >> PNG_SKIP_sRGB_CHECK_PROFILE) & 3) == 2293 PNG_OPTION_ON) 2294 return 0; 2295 #endif 2296 2297 for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i) 2298 { 2299 if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] && 2300 png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] && 2301 png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] && 2302 png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3]) 2303 { 2304 /* This may be one of the old HP profiles without an MD5, in that 2305 * case we can only use the length and Adler32 (note that these 2306 * are not used by default if there is an MD5!) 2307 */ 2308 # if PNG_sRGB_PROFILE_CHECKS == 0 2309 if (png_sRGB_checks[i].have_md5 != 0) 2310 return 1+png_sRGB_checks[i].is_broken; 2311 # endif 2312 2313 /* Profile is unsigned or more checks have been configured in. */ 2314 if (length == 0) 2315 { 2316 length = png_get_uint_32(profile); 2317 intent = png_get_uint_32(profile+64); 2318 } 2319 2320 /* Length *and* intent must match */ 2321 if (length == (png_uint_32) png_sRGB_checks[i].length && 2322 intent == (png_uint_32) png_sRGB_checks[i].intent) 2323 { 2324 /* Now calculate the adler32 if not done already. */ 2325 if (adler == 0) 2326 { 2327 adler = adler32(0, NULL, 0); 2328 adler = adler32(adler, profile, length); 2329 } 2330 2331 if (adler == png_sRGB_checks[i].adler) 2332 { 2333 /* These basic checks suggest that the data has not been 2334 * modified, but if the check level is more than 1 perform 2335 * our own crc32 checksum on the data. 2336 */ 2337 # if PNG_sRGB_PROFILE_CHECKS > 1 2338 if (crc == 0) 2339 { 2340 crc = crc32(0, NULL, 0); 2341 crc = crc32(crc, profile, length); 2342 } 2343 2344 /* So this check must pass for the 'return' below to happen. 2345 */ 2346 if (crc == png_sRGB_checks[i].crc) 2347 # endif 2348 { 2349 if (png_sRGB_checks[i].is_broken != 0) 2350 { 2351 /* These profiles are known to have bad data that may cause 2352 * problems if they are used, therefore attempt to 2353 * discourage their use, skip the 'have_md5' warning below, 2354 * which is made irrelevant by this error. 2355 */ 2356 png_chunk_report(png_ptr, "known incorrect sRGB profile", 2357 PNG_CHUNK_ERROR); 2358 } 2359 2360 /* Warn that this being done; this isn't even an error since 2361 * the profile is perfectly valid, but it would be nice if 2362 * people used the up-to-date ones. 2363 */ 2364 else if (png_sRGB_checks[i].have_md5 == 0) 2365 { 2366 png_chunk_report(png_ptr, 2367 "out-of-date sRGB profile with no signature", 2368 PNG_CHUNK_WARNING); 2369 } 2370 2371 return 1+png_sRGB_checks[i].is_broken; 2372 } 2373 } 2374 2375 # if PNG_sRGB_PROFILE_CHECKS > 0 2376 /* The signature matched, but the profile had been changed in some 2377 * way. This probably indicates a data error or uninformed hacking. 2378 * Fall through to "no match". 2379 */ 2380 png_chunk_report(png_ptr, 2381 "Not recognizing known sRGB profile that has been edited", 2382 PNG_CHUNK_WARNING); 2383 break; 2384 # endif 2385 } 2386 } 2387 } 2388 2389 return 0; /* no match */ 2390 } 2391 2392 void /* PRIVATE */ 2393 png_icc_set_sRGB(png_const_structrp png_ptr, 2394 png_colorspacerp colorspace, png_const_bytep profile, uLong adler) 2395 { 2396 /* Is this profile one of the known ICC sRGB profiles? If it is, just set 2397 * the sRGB information. 2398 */ 2399 if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler) != 0) 2400 (void)png_colorspace_set_sRGB(png_ptr, colorspace, 2401 (int)/*already checked*/png_get_uint_32(profile+64)); 2402 } 2403 #endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */ 2404 #endif /* sRGB */ 2405 2406 int /* PRIVATE */ 2407 png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace, 2408 png_const_charp name, png_uint_32 profile_length, png_const_bytep profile, 2409 int color_type) 2410 { 2411 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) 2412 return 0; 2413 2414 if (icc_check_length(png_ptr, colorspace, name, profile_length) != 0 && 2415 png_icc_check_header(png_ptr, colorspace, name, profile_length, profile, 2416 color_type) != 0 && 2417 png_icc_check_tag_table(png_ptr, colorspace, name, profile_length, 2418 profile) != 0) 2419 { 2420 # if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0 2421 /* If no sRGB support, don't try storing sRGB information */ 2422 png_icc_set_sRGB(png_ptr, colorspace, profile, 0); 2423 # endif 2424 return 1; 2425 } 2426 2427 /* Failure case */ 2428 return 0; 2429 } 2430 #endif /* iCCP */ 2431 2432 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED 2433 void /* PRIVATE */ 2434 png_colorspace_set_rgb_coefficients(png_structrp png_ptr) 2435 { 2436 /* Set the rgb_to_gray coefficients from the colorspace. */ 2437 if (png_ptr->rgb_to_gray_coefficients_set == 0 && 2438 (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) 2439 { 2440 /* png_set_background has not been called, get the coefficients from the Y 2441 * values of the colorspace colorants. 2442 */ 2443 png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y; 2444 png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y; 2445 png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y; 2446 png_fixed_point total = r+g+b; 2447 2448 if (total > 0 && 2449 r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 && 2450 g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 && 2451 b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 && 2452 r+g+b <= 32769) 2453 { 2454 /* We allow 0 coefficients here. r+g+b may be 32769 if two or 2455 * all of the coefficients were rounded up. Handle this by 2456 * reducing the *largest* coefficient by 1; this matches the 2457 * approach used for the default coefficients in pngrtran.c 2458 */ 2459 int add = 0; 2460 2461 if (r+g+b > 32768) 2462 add = -1; 2463 else if (r+g+b < 32768) 2464 add = 1; 2465 2466 if (add != 0) 2467 { 2468 if (g >= r && g >= b) 2469 g += add; 2470 else if (r >= g && r >= b) 2471 r += add; 2472 else 2473 b += add; 2474 } 2475 2476 /* Check for an internal error. */ 2477 if (r+g+b != 32768) 2478 png_error(png_ptr, 2479 "internal error handling cHRM coefficients"); 2480 2481 else 2482 { 2483 png_ptr->rgb_to_gray_red_coeff = (png_uint_16)r; 2484 png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g; 2485 } 2486 } 2487 2488 /* This is a png_error at present even though it could be ignored - 2489 * it should never happen, but it is important that if it does, the 2490 * bug is fixed. 2491 */ 2492 else 2493 png_error(png_ptr, "internal error handling cHRM->XYZ"); 2494 } 2495 } 2496 #endif /* READ_RGB_TO_GRAY */ 2497 2498 #endif /* COLORSPACE */ 2499 2500 #ifdef __GNUC__ 2501 /* This exists solely to work round a warning from GNU C. */ 2502 static int /* PRIVATE */ 2503 png_gt(size_t a, size_t b) 2504 { 2505 return a > b; 2506 } 2507 #else 2508 # define png_gt(a,b) ((a) > (b)) 2509 #endif 2510 2511 void /* PRIVATE */ 2512 png_check_IHDR(png_const_structrp png_ptr, 2513 png_uint_32 width, png_uint_32 height, int bit_depth, 2514 int color_type, int interlace_type, int compression_type, 2515 int filter_type) 2516 { 2517 int error = 0; 2518 2519 /* Check for width and height valid values */ 2520 if (width == 0) 2521 { 2522 png_warning(png_ptr, "Image width is zero in IHDR"); 2523 error = 1; 2524 } 2525 2526 if (width > PNG_UINT_31_MAX) 2527 { 2528 png_warning(png_ptr, "Invalid image width in IHDR"); 2529 error = 1; 2530 } 2531 2532 if (png_gt(((width + 7) & (~7)), 2533 ((PNG_SIZE_MAX 2534 - 48 /* big_row_buf hack */ 2535 - 1) /* filter byte */ 2536 / 8) /* 8-byte RGBA pixels */ 2537 - 1)) /* extra max_pixel_depth pad */ 2538 { 2539 /* The size of the row must be within the limits of this architecture. 2540 * Because the read code can perform arbitrary transformations the 2541 * maximum size is checked here. Because the code in png_read_start_row 2542 * adds extra space "for safety's sake" in several places a conservative 2543 * limit is used here. 2544 * 2545 * NOTE: it would be far better to check the size that is actually used, 2546 * but the effect in the real world is minor and the changes are more 2547 * extensive, therefore much more dangerous and much more difficult to 2548 * write in a way that avoids compiler warnings. 2549 */ 2550 png_warning(png_ptr, "Image width is too large for this architecture"); 2551 error = 1; 2552 } 2553 2554 #ifdef PNG_SET_USER_LIMITS_SUPPORTED 2555 if (width > png_ptr->user_width_max) 2556 #else 2557 if (width > PNG_USER_WIDTH_MAX) 2558 #endif 2559 { 2560 png_warning(png_ptr, "Image width exceeds user limit in IHDR"); 2561 error = 1; 2562 } 2563 2564 if (height == 0) 2565 { 2566 png_warning(png_ptr, "Image height is zero in IHDR"); 2567 error = 1; 2568 } 2569 2570 if (height > PNG_UINT_31_MAX) 2571 { 2572 png_warning(png_ptr, "Invalid image height in IHDR"); 2573 error = 1; 2574 } 2575 2576 #ifdef PNG_SET_USER_LIMITS_SUPPORTED 2577 if (height > png_ptr->user_height_max) 2578 #else 2579 if (height > PNG_USER_HEIGHT_MAX) 2580 #endif 2581 { 2582 png_warning(png_ptr, "Image height exceeds user limit in IHDR"); 2583 error = 1; 2584 } 2585 2586 /* Check other values */ 2587 if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && 2588 bit_depth != 8 && bit_depth != 16) 2589 { 2590 png_warning(png_ptr, "Invalid bit depth in IHDR"); 2591 error = 1; 2592 } 2593 2594 if (color_type < 0 || color_type == 1 || 2595 color_type == 5 || color_type > 6) 2596 { 2597 png_warning(png_ptr, "Invalid color type in IHDR"); 2598 error = 1; 2599 } 2600 2601 if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) || 2602 ((color_type == PNG_COLOR_TYPE_RGB || 2603 color_type == PNG_COLOR_TYPE_GRAY_ALPHA || 2604 color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8)) 2605 { 2606 png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR"); 2607 error = 1; 2608 } 2609 2610 if (interlace_type >= PNG_INTERLACE_LAST) 2611 { 2612 png_warning(png_ptr, "Unknown interlace method in IHDR"); 2613 error = 1; 2614 } 2615 2616 if (compression_type != PNG_COMPRESSION_TYPE_BASE) 2617 { 2618 png_warning(png_ptr, "Unknown compression method in IHDR"); 2619 error = 1; 2620 } 2621 2622 #ifdef PNG_MNG_FEATURES_SUPPORTED 2623 /* Accept filter_method 64 (intrapixel differencing) only if 2624 * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and 2625 * 2. Libpng did not read a PNG signature (this filter_method is only 2626 * used in PNG datastreams that are embedded in MNG datastreams) and 2627 * 3. The application called png_permit_mng_features with a mask that 2628 * included PNG_FLAG_MNG_FILTER_64 and 2629 * 4. The filter_method is 64 and 2630 * 5. The color_type is RGB or RGBA 2631 */ 2632 if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && 2633 png_ptr->mng_features_permitted != 0) 2634 png_warning(png_ptr, "MNG features are not allowed in a PNG datastream"); 2635 2636 if (filter_type != PNG_FILTER_TYPE_BASE) 2637 { 2638 if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 && 2639 (filter_type == PNG_INTRAPIXEL_DIFFERENCING) && 2640 ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) && 2641 (color_type == PNG_COLOR_TYPE_RGB || 2642 color_type == PNG_COLOR_TYPE_RGB_ALPHA))) 2643 { 2644 png_warning(png_ptr, "Unknown filter method in IHDR"); 2645 error = 1; 2646 } 2647 2648 if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0) 2649 { 2650 png_warning(png_ptr, "Invalid filter method in IHDR"); 2651 error = 1; 2652 } 2653 } 2654 2655 #else 2656 if (filter_type != PNG_FILTER_TYPE_BASE) 2657 { 2658 png_warning(png_ptr, "Unknown filter method in IHDR"); 2659 error = 1; 2660 } 2661 #endif 2662 2663 if (error == 1) 2664 png_error(png_ptr, "Invalid IHDR data"); 2665 } 2666 2667 #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED) 2668 /* ASCII to fp functions */ 2669 /* Check an ASCII formated floating point value, see the more detailed 2670 * comments in pngpriv.h 2671 */ 2672 /* The following is used internally to preserve the sticky flags */ 2673 #define png_fp_add(state, flags) ((state) |= (flags)) 2674 #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY)) 2675 2676 int /* PRIVATE */ 2677 png_check_fp_number(png_const_charp string, png_size_t size, int *statep, 2678 png_size_tp whereami) 2679 { 2680 int state = *statep; 2681 png_size_t i = *whereami; 2682 2683 while (i < size) 2684 { 2685 int type; 2686 /* First find the type of the next character */ 2687 switch (string[i]) 2688 { 2689 case 43: type = PNG_FP_SAW_SIGN; break; 2690 case 45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break; 2691 case 46: type = PNG_FP_SAW_DOT; break; 2692 case 48: type = PNG_FP_SAW_DIGIT; break; 2693 case 49: case 50: case 51: case 52: 2694 case 53: case 54: case 55: case 56: 2695 case 57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break; 2696 case 69: 2697 case 101: type = PNG_FP_SAW_E; break; 2698 default: goto PNG_FP_End; 2699 } 2700 2701 /* Now deal with this type according to the current 2702 * state, the type is arranged to not overlap the 2703 * bits of the PNG_FP_STATE. 2704 */ 2705 switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY)) 2706 { 2707 case PNG_FP_INTEGER + PNG_FP_SAW_SIGN: 2708 if ((state & PNG_FP_SAW_ANY) != 0) 2709 goto PNG_FP_End; /* not a part of the number */ 2710 2711 png_fp_add(state, type); 2712 break; 2713 2714 case PNG_FP_INTEGER + PNG_FP_SAW_DOT: 2715 /* Ok as trailer, ok as lead of fraction. */ 2716 if ((state & PNG_FP_SAW_DOT) != 0) /* two dots */ 2717 goto PNG_FP_End; 2718 2719 else if ((state & PNG_FP_SAW_DIGIT) != 0) /* trailing dot? */ 2720 png_fp_add(state, type); 2721 2722 else 2723 png_fp_set(state, PNG_FP_FRACTION | type); 2724 2725 break; 2726 2727 case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT: 2728 if ((state & PNG_FP_SAW_DOT) != 0) /* delayed fraction */ 2729 png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT); 2730 2731 png_fp_add(state, type | PNG_FP_WAS_VALID); 2732 2733 break; 2734 2735 case PNG_FP_INTEGER + PNG_FP_SAW_E: 2736 if ((state & PNG_FP_SAW_DIGIT) == 0) 2737 goto PNG_FP_End; 2738 2739 png_fp_set(state, PNG_FP_EXPONENT); 2740 2741 break; 2742 2743 /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN: 2744 goto PNG_FP_End; ** no sign in fraction */ 2745 2746 /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT: 2747 goto PNG_FP_End; ** Because SAW_DOT is always set */ 2748 2749 case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT: 2750 png_fp_add(state, type | PNG_FP_WAS_VALID); 2751 break; 2752 2753 case PNG_FP_FRACTION + PNG_FP_SAW_E: 2754 /* This is correct because the trailing '.' on an 2755 * integer is handled above - so we can only get here 2756 * with the sequence ".E" (with no preceding digits). 2757 */ 2758 if ((state & PNG_FP_SAW_DIGIT) == 0) 2759 goto PNG_FP_End; 2760 2761 png_fp_set(state, PNG_FP_EXPONENT); 2762 2763 break; 2764 2765 case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN: 2766 if ((state & PNG_FP_SAW_ANY) != 0) 2767 goto PNG_FP_End; /* not a part of the number */ 2768 2769 png_fp_add(state, PNG_FP_SAW_SIGN); 2770 2771 break; 2772 2773 /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT: 2774 goto PNG_FP_End; */ 2775 2776 case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT: 2777 png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID); 2778 2779 break; 2780 2781 /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E: 2782 goto PNG_FP_End; */ 2783 2784 default: goto PNG_FP_End; /* I.e. break 2 */ 2785 } 2786 2787 /* The character seems ok, continue. */ 2788 ++i; 2789 } 2790 2791 PNG_FP_End: 2792 /* Here at the end, update the state and return the correct 2793 * return code. 2794 */ 2795 *statep = state; 2796 *whereami = i; 2797 2798 return (state & PNG_FP_SAW_DIGIT) != 0; 2799 } 2800 2801 2802 /* The same but for a complete string. */ 2803 int 2804 png_check_fp_string(png_const_charp string, png_size_t size) 2805 { 2806 int state=0; 2807 png_size_t char_index=0; 2808 2809 if (png_check_fp_number(string, size, &state, &char_index) != 0 && 2810 (char_index == size || string[char_index] == 0)) 2811 return state /* must be non-zero - see above */; 2812 2813 return 0; /* i.e. fail */ 2814 } 2815 #endif /* pCAL || sCAL */ 2816 2817 #ifdef PNG_sCAL_SUPPORTED 2818 # ifdef PNG_FLOATING_POINT_SUPPORTED 2819 /* Utility used below - a simple accurate power of ten from an integral 2820 * exponent. 2821 */ 2822 static double 2823 png_pow10(int power) 2824 { 2825 int recip = 0; 2826 double d = 1; 2827 2828 /* Handle negative exponent with a reciprocal at the end because 2829 * 10 is exact whereas .1 is inexact in base 2 2830 */ 2831 if (power < 0) 2832 { 2833 if (power < DBL_MIN_10_EXP) return 0; 2834 recip = 1, power = -power; 2835 } 2836 2837 if (power > 0) 2838 { 2839 /* Decompose power bitwise. */ 2840 double mult = 10; 2841 do 2842 { 2843 if (power & 1) d *= mult; 2844 mult *= mult; 2845 power >>= 1; 2846 } 2847 while (power > 0); 2848 2849 if (recip != 0) d = 1/d; 2850 } 2851 /* else power is 0 and d is 1 */ 2852 2853 return d; 2854 } 2855 2856 /* Function to format a floating point value in ASCII with a given 2857 * precision. 2858 */ 2859 void /* PRIVATE */ 2860 png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size, 2861 double fp, unsigned int precision) 2862 { 2863 /* We use standard functions from math.h, but not printf because 2864 * that would require stdio. The caller must supply a buffer of 2865 * sufficient size or we will png_error. The tests on size and 2866 * the space in ascii[] consumed are indicated below. 2867 */ 2868 if (precision < 1) 2869 precision = DBL_DIG; 2870 2871 /* Enforce the limit of the implementation precision too. */ 2872 if (precision > DBL_DIG+1) 2873 precision = DBL_DIG+1; 2874 2875 /* Basic sanity checks */ 2876 if (size >= precision+5) /* See the requirements below. */ 2877 { 2878 if (fp < 0) 2879 { 2880 fp = -fp; 2881 *ascii++ = 45; /* '-' PLUS 1 TOTAL 1 */ 2882 --size; 2883 } 2884 2885 if (fp >= DBL_MIN && fp <= DBL_MAX) 2886 { 2887 int exp_b10; /* A base 10 exponent */ 2888 double base; /* 10^exp_b10 */ 2889 2890 /* First extract a base 10 exponent of the number, 2891 * the calculation below rounds down when converting 2892 * from base 2 to base 10 (multiply by log10(2) - 2893 * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to 2894 * be increased. Note that the arithmetic shift 2895 * performs a floor() unlike C arithmetic - using a 2896 * C multiply would break the following for negative 2897 * exponents. 2898 */ 2899 (void)frexp(fp, &exp_b10); /* exponent to base 2 */ 2900 2901 exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */ 2902 2903 /* Avoid underflow here. */ 2904 base = png_pow10(exp_b10); /* May underflow */ 2905 2906 while (base < DBL_MIN || base < fp) 2907 { 2908 /* And this may overflow. */ 2909 double test = png_pow10(exp_b10+1); 2910 2911 if (test <= DBL_MAX) 2912 ++exp_b10, base = test; 2913 2914 else 2915 break; 2916 } 2917 2918 /* Normalize fp and correct exp_b10, after this fp is in the 2919 * range [.1,1) and exp_b10 is both the exponent and the digit 2920 * *before* which the decimal point should be inserted 2921 * (starting with 0 for the first digit). Note that this 2922 * works even if 10^exp_b10 is out of range because of the 2923 * test on DBL_MAX above. 2924 */ 2925 fp /= base; 2926 while (fp >= 1) fp /= 10, ++exp_b10; 2927 2928 /* Because of the code above fp may, at this point, be 2929 * less than .1, this is ok because the code below can 2930 * handle the leading zeros this generates, so no attempt 2931 * is made to correct that here. 2932 */ 2933 2934 { 2935 unsigned int czero, clead, cdigits; 2936 char exponent[10]; 2937 2938 /* Allow up to two leading zeros - this will not lengthen 2939 * the number compared to using E-n. 2940 */ 2941 if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */ 2942 { 2943 czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */ 2944 exp_b10 = 0; /* Dot added below before first output. */ 2945 } 2946 else 2947 czero = 0; /* No zeros to add */ 2948 2949 /* Generate the digit list, stripping trailing zeros and 2950 * inserting a '.' before a digit if the exponent is 0. 2951 */ 2952 clead = czero; /* Count of leading zeros */ 2953 cdigits = 0; /* Count of digits in list. */ 2954 2955 do 2956 { 2957 double d; 2958 2959 fp *= 10; 2960 /* Use modf here, not floor and subtract, so that 2961 * the separation is done in one step. At the end 2962 * of the loop don't break the number into parts so 2963 * that the final digit is rounded. 2964 */ 2965 if (cdigits+czero+1 < precision+clead) 2966 fp = modf(fp, &d); 2967 2968 else 2969 { 2970 d = floor(fp + .5); 2971 2972 if (d > 9) 2973 { 2974 /* Rounding up to 10, handle that here. */ 2975 if (czero > 0) 2976 { 2977 --czero, d = 1; 2978 if (cdigits == 0) --clead; 2979 } 2980 else 2981 { 2982 while (cdigits > 0 && d > 9) 2983 { 2984 int ch = *--ascii; 2985 2986 if (exp_b10 != (-1)) 2987 ++exp_b10; 2988 2989 else if (ch == 46) 2990 { 2991 ch = *--ascii, ++size; 2992 /* Advance exp_b10 to '1', so that the 2993 * decimal point happens after the 2994 * previous digit. 2995 */ 2996 exp_b10 = 1; 2997 } 2998 2999 --cdigits; 3000 d = ch - 47; /* I.e. 1+(ch-48) */ 3001 } 3002 3003 /* Did we reach the beginning? If so adjust the 3004 * exponent but take into account the leading 3005 * decimal point. 3006 */ 3007 if (d > 9) /* cdigits == 0 */ 3008 { 3009 if (exp_b10 == (-1)) 3010 { 3011 /* Leading decimal point (plus zeros?), if 3012 * we lose the decimal point here it must 3013 * be reentered below. 3014 */ 3015 int ch = *--ascii; 3016 3017 if (ch == 46) 3018 ++size, exp_b10 = 1; 3019 3020 /* Else lost a leading zero, so 'exp_b10' is 3021 * still ok at (-1) 3022 */ 3023 } 3024 else 3025 ++exp_b10; 3026 3027 /* In all cases we output a '1' */ 3028 d = 1; 3029 } 3030 } 3031 } 3032 fp = 0; /* Guarantees termination below. */ 3033 } 3034 3035 if (d == 0) 3036 { 3037 ++czero; 3038 if (cdigits == 0) ++clead; 3039 } 3040 else 3041 { 3042 /* Included embedded zeros in the digit count. */ 3043 cdigits += czero - clead; 3044 clead = 0; 3045 3046 while (czero > 0) 3047 { 3048 /* exp_b10 == (-1) means we just output the decimal 3049 * place - after the DP don't adjust 'exp_b10' any 3050 * more! 3051 */ 3052 if (exp_b10 != (-1)) 3053 { 3054 if (exp_b10 == 0) *ascii++ = 46, --size; 3055 /* PLUS 1: TOTAL 4 */ 3056 --exp_b10; 3057 } 3058 *ascii++ = 48, --czero; 3059 } 3060 3061 if (exp_b10 != (-1)) 3062 { 3063 if (exp_b10 == 0) 3064 *ascii++ = 46, --size; /* counted above */ 3065 3066 --exp_b10; 3067 } 3068 *ascii++ = (char)(48 + (int)d), ++cdigits; 3069 } 3070 } 3071 while (cdigits+czero < precision+clead && fp > DBL_MIN); 3072 3073 /* The total output count (max) is now 4+precision */ 3074 3075 /* Check for an exponent, if we don't need one we are 3076 * done and just need to terminate the string. At 3077 * this point exp_b10==(-1) is effectively if flag - it got 3078 * to '-1' because of the decrement after outputting 3079 * the decimal point above (the exponent required is 3080 * *not* -1!) 3081 */ 3082 if (exp_b10 >= (-1) && exp_b10 <= 2) 3083 { 3084 /* The following only happens if we didn't output the 3085 * leading zeros above for negative exponent, so this 3086 * doesn't add to the digit requirement. Note that the 3087 * two zeros here can only be output if the two leading 3088 * zeros were *not* output, so this doesn't increase 3089 * the output count. 3090 */ 3091 while (--exp_b10 >= 0) *ascii++ = 48; 3092 3093 *ascii = 0; 3094 3095 /* Total buffer requirement (including the '\0') is 3096 * 5+precision - see check at the start. 3097 */ 3098 return; 3099 } 3100 3101 /* Here if an exponent is required, adjust size for 3102 * the digits we output but did not count. The total 3103 * digit output here so far is at most 1+precision - no 3104 * decimal point and no leading or trailing zeros have 3105 * been output. 3106 */ 3107 size -= cdigits; 3108 3109 *ascii++ = 69, --size; /* 'E': PLUS 1 TOTAL 2+precision */ 3110 3111 /* The following use of an unsigned temporary avoids ambiguities in 3112 * the signed arithmetic on exp_b10 and permits GCC at least to do 3113 * better optimization. 3114 */ 3115 { 3116 unsigned int uexp_b10; 3117 3118 if (exp_b10 < 0) 3119 { 3120 *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */ 3121 uexp_b10 = -exp_b10; 3122 } 3123 3124 else 3125 uexp_b10 = exp_b10; 3126 3127 cdigits = 0; 3128 3129 while (uexp_b10 > 0) 3130 { 3131 exponent[cdigits++] = (char)(48 + uexp_b10 % 10); 3132 uexp_b10 /= 10; 3133 } 3134 } 3135 3136 /* Need another size check here for the exponent digits, so 3137 * this need not be considered above. 3138 */ 3139 if (size > cdigits) 3140 { 3141 while (cdigits > 0) *ascii++ = exponent[--cdigits]; 3142 3143 *ascii = 0; 3144 3145 return; 3146 } 3147 } 3148 } 3149 else if (!(fp >= DBL_MIN)) 3150 { 3151 *ascii++ = 48; /* '0' */ 3152 *ascii = 0; 3153 return; 3154 } 3155 else 3156 { 3157 *ascii++ = 105; /* 'i' */ 3158 *ascii++ = 110; /* 'n' */ 3159 *ascii++ = 102; /* 'f' */ 3160 *ascii = 0; 3161 return; 3162 } 3163 } 3164 3165 /* Here on buffer too small. */ 3166 png_error(png_ptr, "ASCII conversion buffer too small"); 3167 } 3168 3169 # endif /* FLOATING_POINT */ 3170 3171 # ifdef PNG_FIXED_POINT_SUPPORTED 3172 /* Function to format a fixed point value in ASCII. 3173 */ 3174 void /* PRIVATE */ 3175 png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii, 3176 png_size_t size, png_fixed_point fp) 3177 { 3178 /* Require space for 10 decimal digits, a decimal point, a minus sign and a 3179 * trailing \0, 13 characters: 3180 */ 3181 if (size > 12) 3182 { 3183 png_uint_32 num; 3184 3185 /* Avoid overflow here on the minimum integer. */ 3186 if (fp < 0) 3187 *ascii++ = 45, num = -fp; 3188 else 3189 num = fp; 3190 3191 if (num <= 0x80000000) /* else overflowed */ 3192 { 3193 unsigned int ndigits = 0, first = 16 /* flag value */; 3194 char digits[10]; 3195 3196 while (num) 3197 { 3198 /* Split the low digit off num: */ 3199 unsigned int tmp = num/10; 3200 num -= tmp*10; 3201 digits[ndigits++] = (char)(48 + num); 3202 /* Record the first non-zero digit, note that this is a number 3203 * starting at 1, it's not actually the array index. 3204 */ 3205 if (first == 16 && num > 0) 3206 first = ndigits; 3207 num = tmp; 3208 } 3209 3210 if (ndigits > 0) 3211 { 3212 while (ndigits > 5) *ascii++ = digits[--ndigits]; 3213 /* The remaining digits are fractional digits, ndigits is '5' or 3214 * smaller at this point. It is certainly not zero. Check for a 3215 * non-zero fractional digit: 3216 */ 3217 if (first <= 5) 3218 { 3219 unsigned int i; 3220 *ascii++ = 46; /* decimal point */ 3221 /* ndigits may be <5 for small numbers, output leading zeros 3222 * then ndigits digits to first: 3223 */ 3224 i = 5; 3225 while (ndigits < i) *ascii++ = 48, --i; 3226 while (ndigits >= first) *ascii++ = digits[--ndigits]; 3227 /* Don't output the trailing zeros! */ 3228 } 3229 } 3230 else 3231 *ascii++ = 48; 3232 3233 /* And null terminate the string: */ 3234 *ascii = 0; 3235 return; 3236 } 3237 } 3238 3239 /* Here on buffer too small. */ 3240 png_error(png_ptr, "ASCII conversion buffer too small"); 3241 } 3242 # endif /* FIXED_POINT */ 3243 #endif /* SCAL */ 3244 3245 #if defined(PNG_FLOATING_POINT_SUPPORTED) && \ 3246 !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \ 3247 (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \ 3248 defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \ 3249 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \ 3250 (defined(PNG_sCAL_SUPPORTED) && \ 3251 defined(PNG_FLOATING_ARITHMETIC_SUPPORTED)) 3252 png_fixed_point 3253 png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text) 3254 { 3255 double r = floor(100000 * fp + .5); 3256 3257 if (r > 2147483647. || r < -2147483648.) 3258 png_fixed_error(png_ptr, text); 3259 3260 # ifndef PNG_ERROR_TEXT_SUPPORTED 3261 PNG_UNUSED(text) 3262 # endif 3263 3264 return (png_fixed_point)r; 3265 } 3266 #endif 3267 3268 #if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\ 3269 defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED) 3270 /* muldiv functions */ 3271 /* This API takes signed arguments and rounds the result to the nearest 3272 * integer (or, for a fixed point number - the standard argument - to 3273 * the nearest .00001). Overflow and divide by zero are signalled in 3274 * the result, a boolean - true on success, false on overflow. 3275 */ 3276 int 3277 png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times, 3278 png_int_32 divisor) 3279 { 3280 /* Return a * times / divisor, rounded. */ 3281 if (divisor != 0) 3282 { 3283 if (a == 0 || times == 0) 3284 { 3285 *res = 0; 3286 return 1; 3287 } 3288 else 3289 { 3290 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3291 double r = a; 3292 r *= times; 3293 r /= divisor; 3294 r = floor(r+.5); 3295 3296 /* A png_fixed_point is a 32-bit integer. */ 3297 if (r <= 2147483647. && r >= -2147483648.) 3298 { 3299 *res = (png_fixed_point)r; 3300 return 1; 3301 } 3302 #else 3303 int negative = 0; 3304 png_uint_32 A, T, D; 3305 png_uint_32 s16, s32, s00; 3306 3307 if (a < 0) 3308 negative = 1, A = -a; 3309 else 3310 A = a; 3311 3312 if (times < 0) 3313 negative = !negative, T = -times; 3314 else 3315 T = times; 3316 3317 if (divisor < 0) 3318 negative = !negative, D = -divisor; 3319 else 3320 D = divisor; 3321 3322 /* Following can't overflow because the arguments only 3323 * have 31 bits each, however the result may be 32 bits. 3324 */ 3325 s16 = (A >> 16) * (T & 0xffff) + 3326 (A & 0xffff) * (T >> 16); 3327 /* Can't overflow because the a*times bit is only 30 3328 * bits at most. 3329 */ 3330 s32 = (A >> 16) * (T >> 16) + (s16 >> 16); 3331 s00 = (A & 0xffff) * (T & 0xffff); 3332 3333 s16 = (s16 & 0xffff) << 16; 3334 s00 += s16; 3335 3336 if (s00 < s16) 3337 ++s32; /* carry */ 3338 3339 if (s32 < D) /* else overflow */ 3340 { 3341 /* s32.s00 is now the 64-bit product, do a standard 3342 * division, we know that s32 < D, so the maximum 3343 * required shift is 31. 3344 */ 3345 int bitshift = 32; 3346 png_fixed_point result = 0; /* NOTE: signed */ 3347 3348 while (--bitshift >= 0) 3349 { 3350 png_uint_32 d32, d00; 3351 3352 if (bitshift > 0) 3353 d32 = D >> (32-bitshift), d00 = D << bitshift; 3354 3355 else 3356 d32 = 0, d00 = D; 3357 3358 if (s32 > d32) 3359 { 3360 if (s00 < d00) --s32; /* carry */ 3361 s32 -= d32, s00 -= d00, result += 1<<bitshift; 3362 } 3363 3364 else 3365 if (s32 == d32 && s00 >= d00) 3366 s32 = 0, s00 -= d00, result += 1<<bitshift; 3367 } 3368 3369 /* Handle the rounding. */ 3370 if (s00 >= (D >> 1)) 3371 ++result; 3372 3373 if (negative != 0) 3374 result = -result; 3375 3376 /* Check for overflow. */ 3377 if ((negative != 0 && result <= 0) || 3378 (negative == 0 && result >= 0)) 3379 { 3380 *res = result; 3381 return 1; 3382 } 3383 } 3384 #endif 3385 } 3386 } 3387 3388 return 0; 3389 } 3390 #endif /* READ_GAMMA || INCH_CONVERSIONS */ 3391 3392 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED) 3393 /* The following is for when the caller doesn't much care about the 3394 * result. 3395 */ 3396 png_fixed_point 3397 png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times, 3398 png_int_32 divisor) 3399 { 3400 png_fixed_point result; 3401 3402 if (png_muldiv(&result, a, times, divisor) != 0) 3403 return result; 3404 3405 png_warning(png_ptr, "fixed point overflow ignored"); 3406 return 0; 3407 } 3408 #endif 3409 3410 #ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */ 3411 /* Calculate a reciprocal, return 0 on div-by-zero or overflow. */ 3412 png_fixed_point 3413 png_reciprocal(png_fixed_point a) 3414 { 3415 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3416 double r = floor(1E10/a+.5); 3417 3418 if (r <= 2147483647. && r >= -2147483648.) 3419 return (png_fixed_point)r; 3420 #else 3421 png_fixed_point res; 3422 3423 if (png_muldiv(&res, 100000, 100000, a) != 0) 3424 return res; 3425 #endif 3426 3427 return 0; /* error/overflow */ 3428 } 3429 3430 /* This is the shared test on whether a gamma value is 'significant' - whether 3431 * it is worth doing gamma correction. 3432 */ 3433 int /* PRIVATE */ 3434 png_gamma_significant(png_fixed_point gamma_val) 3435 { 3436 return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED || 3437 gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED; 3438 } 3439 #endif 3440 3441 #ifdef PNG_READ_GAMMA_SUPPORTED 3442 #ifdef PNG_16BIT_SUPPORTED 3443 /* A local convenience routine. */ 3444 static png_fixed_point 3445 png_product2(png_fixed_point a, png_fixed_point b) 3446 { 3447 /* The required result is 1/a * 1/b; the following preserves accuracy. */ 3448 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3449 double r = a * 1E-5; 3450 r *= b; 3451 r = floor(r+.5); 3452 3453 if (r <= 2147483647. && r >= -2147483648.) 3454 return (png_fixed_point)r; 3455 #else 3456 png_fixed_point res; 3457 3458 if (png_muldiv(&res, a, b, 100000) != 0) 3459 return res; 3460 #endif 3461 3462 return 0; /* overflow */ 3463 } 3464 #endif /* 16BIT */ 3465 3466 /* The inverse of the above. */ 3467 png_fixed_point 3468 png_reciprocal2(png_fixed_point a, png_fixed_point b) 3469 { 3470 /* The required result is 1/a * 1/b; the following preserves accuracy. */ 3471 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3472 if (a != 0 && b != 0) 3473 { 3474 double r = 1E15/a; 3475 r /= b; 3476 r = floor(r+.5); 3477 3478 if (r <= 2147483647. && r >= -2147483648.) 3479 return (png_fixed_point)r; 3480 } 3481 #else 3482 /* This may overflow because the range of png_fixed_point isn't symmetric, 3483 * but this API is only used for the product of file and screen gamma so it 3484 * doesn't matter that the smallest number it can produce is 1/21474, not 3485 * 1/100000 3486 */ 3487 png_fixed_point res = png_product2(a, b); 3488 3489 if (res != 0) 3490 return png_reciprocal(res); 3491 #endif 3492 3493 return 0; /* overflow */ 3494 } 3495 #endif /* READ_GAMMA */ 3496 3497 #ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */ 3498 #ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED 3499 /* Fixed point gamma. 3500 * 3501 * The code to calculate the tables used below can be found in the shell script 3502 * contrib/tools/intgamma.sh 3503 * 3504 * To calculate gamma this code implements fast log() and exp() calls using only 3505 * fixed point arithmetic. This code has sufficient precision for either 8-bit 3506 * or 16-bit sample values. 3507 * 3508 * The tables used here were calculated using simple 'bc' programs, but C double 3509 * precision floating point arithmetic would work fine. 3510 * 3511 * 8-bit log table 3512 * This is a table of -log(value/255)/log(2) for 'value' in the range 128 to 3513 * 255, so it's the base 2 logarithm of a normalized 8-bit floating point 3514 * mantissa. The numbers are 32-bit fractions. 3515 */ 3516 static const png_uint_32 3517 png_8bit_l2[128] = 3518 { 3519 4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U, 3520 3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U, 3521 3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U, 3522 3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U, 3523 3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U, 3524 2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U, 3525 2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U, 3526 2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U, 3527 2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U, 3528 2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U, 3529 1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U, 3530 1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U, 3531 1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U, 3532 1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U, 3533 1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U, 3534 971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U, 3535 803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U, 3536 639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U, 3537 479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U, 3538 324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U, 3539 172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U, 3540 24347096U, 0U 3541 3542 #if 0 3543 /* The following are the values for 16-bit tables - these work fine for the 3544 * 8-bit conversions but produce very slightly larger errors in the 16-bit 3545 * log (about 1.2 as opposed to 0.7 absolute error in the final value). To 3546 * use these all the shifts below must be adjusted appropriately. 3547 */ 3548 65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054, 3549 57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803, 3550 50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068, 3551 43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782, 3552 37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887, 3553 31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339, 3554 25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098, 3555 20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132, 3556 15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415, 3557 10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523, 3558 6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495, 3559 1119, 744, 372 3560 #endif 3561 }; 3562 3563 static png_int_32 3564 png_log8bit(unsigned int x) 3565 { 3566 unsigned int lg2 = 0; 3567 /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log, 3568 * because the log is actually negate that means adding 1. The final 3569 * returned value thus has the range 0 (for 255 input) to 7.994 (for 1 3570 * input), return -1 for the overflow (log 0) case, - so the result is 3571 * always at most 19 bits. 3572 */ 3573 if ((x &= 0xff) == 0) 3574 return -1; 3575 3576 if ((x & 0xf0) == 0) 3577 lg2 = 4, x <<= 4; 3578 3579 if ((x & 0xc0) == 0) 3580 lg2 += 2, x <<= 2; 3581 3582 if ((x & 0x80) == 0) 3583 lg2 += 1, x <<= 1; 3584 3585 /* result is at most 19 bits, so this cast is safe: */ 3586 return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16)); 3587 } 3588 3589 /* The above gives exact (to 16 binary places) log2 values for 8-bit images, 3590 * for 16-bit images we use the most significant 8 bits of the 16-bit value to 3591 * get an approximation then multiply the approximation by a correction factor 3592 * determined by the remaining up to 8 bits. This requires an additional step 3593 * in the 16-bit case. 3594 * 3595 * We want log2(value/65535), we have log2(v'/255), where: 3596 * 3597 * value = v' * 256 + v'' 3598 * = v' * f 3599 * 3600 * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128 3601 * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less 3602 * than 258. The final factor also needs to correct for the fact that our 8-bit 3603 * value is scaled by 255, whereas the 16-bit values must be scaled by 65535. 3604 * 3605 * This gives a final formula using a calculated value 'x' which is value/v' and 3606 * scaling by 65536 to match the above table: 3607 * 3608 * log2(x/257) * 65536 3609 * 3610 * Since these numbers are so close to '1' we can use simple linear 3611 * interpolation between the two end values 256/257 (result -368.61) and 258/257 3612 * (result 367.179). The values used below are scaled by a further 64 to give 3613 * 16-bit precision in the interpolation: 3614 * 3615 * Start (256): -23591 3616 * Zero (257): 0 3617 * End (258): 23499 3618 */ 3619 #ifdef PNG_16BIT_SUPPORTED 3620 static png_int_32 3621 png_log16bit(png_uint_32 x) 3622 { 3623 unsigned int lg2 = 0; 3624 3625 /* As above, but now the input has 16 bits. */ 3626 if ((x &= 0xffff) == 0) 3627 return -1; 3628 3629 if ((x & 0xff00) == 0) 3630 lg2 = 8, x <<= 8; 3631 3632 if ((x & 0xf000) == 0) 3633 lg2 += 4, x <<= 4; 3634 3635 if ((x & 0xc000) == 0) 3636 lg2 += 2, x <<= 2; 3637 3638 if ((x & 0x8000) == 0) 3639 lg2 += 1, x <<= 1; 3640 3641 /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional 3642 * value. 3643 */ 3644 lg2 <<= 28; 3645 lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4; 3646 3647 /* Now we need to interpolate the factor, this requires a division by the top 3648 * 8 bits. Do this with maximum precision. 3649 */ 3650 x = ((x << 16) + (x >> 9)) / (x >> 8); 3651 3652 /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24, 3653 * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly 3654 * 16 bits to interpolate to get the low bits of the result. Round the 3655 * answer. Note that the end point values are scaled by 64 to retain overall 3656 * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust 3657 * the overall scaling by 6-12. Round at every step. 3658 */ 3659 x -= 1U << 24; 3660 3661 if (x <= 65536U) /* <= '257' */ 3662 lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12); 3663 3664 else 3665 lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12); 3666 3667 /* Safe, because the result can't have more than 20 bits: */ 3668 return (png_int_32)((lg2 + 2048) >> 12); 3669 } 3670 #endif /* 16BIT */ 3671 3672 /* The 'exp()' case must invert the above, taking a 20-bit fixed point 3673 * logarithmic value and returning a 16 or 8-bit number as appropriate. In 3674 * each case only the low 16 bits are relevant - the fraction - since the 3675 * integer bits (the top 4) simply determine a shift. 3676 * 3677 * The worst case is the 16-bit distinction between 65535 and 65534. This 3678 * requires perhaps spurious accuracy in the decoding of the logarithm to 3679 * distinguish log2(65535/65534.5) - 10^-5 or 17 bits. There is little chance 3680 * of getting this accuracy in practice. 3681 * 3682 * To deal with this the following exp() function works out the exponent of the 3683 * frational part of the logarithm by using an accurate 32-bit value from the 3684 * top four fractional bits then multiplying in the remaining bits. 3685 */ 3686 static const png_uint_32 3687 png_32bit_exp[16] = 3688 { 3689 /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */ 3690 4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U, 3691 3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U, 3692 2553802834U, 2445529972U, 2341847524U, 2242560872U 3693 }; 3694 3695 /* Adjustment table; provided to explain the numbers in the code below. */ 3696 #if 0 3697 for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"} 3698 11 44937.64284865548751208448 3699 10 45180.98734845585101160448 3700 9 45303.31936980687359311872 3701 8 45364.65110595323018870784 3702 7 45395.35850361789624614912 3703 6 45410.72259715102037508096 3704 5 45418.40724413220722311168 3705 4 45422.25021786898173001728 3706 3 45424.17186732298419044352 3707 2 45425.13273269940811464704 3708 1 45425.61317555035558641664 3709 0 45425.85339951654943850496 3710 #endif 3711 3712 static png_uint_32 3713 png_exp(png_fixed_point x) 3714 { 3715 if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */ 3716 { 3717 /* Obtain a 4-bit approximation */ 3718 png_uint_32 e = png_32bit_exp[(x >> 12) & 0x0f]; 3719 3720 /* Incorporate the low 12 bits - these decrease the returned value by 3721 * multiplying by a number less than 1 if the bit is set. The multiplier 3722 * is determined by the above table and the shift. Notice that the values 3723 * converge on 45426 and this is used to allow linear interpolation of the 3724 * low bits. 3725 */ 3726 if (x & 0x800) 3727 e -= (((e >> 16) * 44938U) + 16U) >> 5; 3728 3729 if (x & 0x400) 3730 e -= (((e >> 16) * 45181U) + 32U) >> 6; 3731 3732 if (x & 0x200) 3733 e -= (((e >> 16) * 45303U) + 64U) >> 7; 3734 3735 if (x & 0x100) 3736 e -= (((e >> 16) * 45365U) + 128U) >> 8; 3737 3738 if (x & 0x080) 3739 e -= (((e >> 16) * 45395U) + 256U) >> 9; 3740 3741 if (x & 0x040) 3742 e -= (((e >> 16) * 45410U) + 512U) >> 10; 3743 3744 /* And handle the low 6 bits in a single block. */ 3745 e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9; 3746 3747 /* Handle the upper bits of x. */ 3748 e >>= x >> 16; 3749 return e; 3750 } 3751 3752 /* Check for overflow */ 3753 if (x <= 0) 3754 return png_32bit_exp[0]; 3755 3756 /* Else underflow */ 3757 return 0; 3758 } 3759 3760 static png_byte 3761 png_exp8bit(png_fixed_point lg2) 3762 { 3763 /* Get a 32-bit value: */ 3764 png_uint_32 x = png_exp(lg2); 3765 3766 /* Convert the 32-bit value to 0..255 by multiplying by 256-1. Note that the 3767 * second, rounding, step can't overflow because of the first, subtraction, 3768 * step. 3769 */ 3770 x -= x >> 8; 3771 return (png_byte)(((x + 0x7fffffU) >> 24) & 0xff); 3772 } 3773 3774 #ifdef PNG_16BIT_SUPPORTED 3775 static png_uint_16 3776 png_exp16bit(png_fixed_point lg2) 3777 { 3778 /* Get a 32-bit value: */ 3779 png_uint_32 x = png_exp(lg2); 3780 3781 /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */ 3782 x -= x >> 16; 3783 return (png_uint_16)((x + 32767U) >> 16); 3784 } 3785 #endif /* 16BIT */ 3786 #endif /* FLOATING_ARITHMETIC */ 3787 3788 png_byte 3789 png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val) 3790 { 3791 if (value > 0 && value < 255) 3792 { 3793 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3794 /* 'value' is unsigned, ANSI-C90 requires the compiler to correctly 3795 * convert this to a floating point value. This includes values that 3796 * would overflow if 'value' were to be converted to 'int'. 3797 * 3798 * Apparently GCC, however, does an intermediate conversion to (int) 3799 * on some (ARM) but not all (x86) platforms, possibly because of 3800 * hardware FP limitations. (E.g. if the hardware conversion always 3801 * assumes the integer register contains a signed value.) This results 3802 * in ANSI-C undefined behavior for large values. 3803 * 3804 * Other implementations on the same machine might actually be ANSI-C90 3805 * conformant and therefore compile spurious extra code for the large 3806 * values. 3807 * 3808 * We can be reasonably sure that an unsigned to float conversion 3809 * won't be faster than an int to float one. Therefore this code 3810 * assumes responsibility for the undefined behavior, which it knows 3811 * can't happen because of the check above. 3812 * 3813 * Note the argument to this routine is an (unsigned int) because, on 3814 * 16-bit platforms, it is assigned a value which might be out of 3815 * range for an (int); that would result in undefined behavior in the 3816 * caller if the *argument* ('value') were to be declared (int). 3817 */ 3818 double r = floor(255*pow((int)/*SAFE*/value/255.,gamma_val*.00001)+.5); 3819 return (png_byte)r; 3820 # else 3821 png_int_32 lg2 = png_log8bit(value); 3822 png_fixed_point res; 3823 3824 if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0) 3825 return png_exp8bit(res); 3826 3827 /* Overflow. */ 3828 value = 0; 3829 # endif 3830 } 3831 3832 return (png_byte)(value & 0xff); 3833 } 3834 3835 #ifdef PNG_16BIT_SUPPORTED 3836 png_uint_16 3837 png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val) 3838 { 3839 if (value > 0 && value < 65535) 3840 { 3841 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3842 /* The same (unsigned int)->(double) constraints apply here as above, 3843 * however in this case the (unsigned int) to (int) conversion can 3844 * overflow on an ANSI-C90 compliant system so the cast needs to ensure 3845 * that this is not possible. 3846 */ 3847 double r = floor(65535*pow((png_int_32)value/65535., 3848 gamma_val*.00001)+.5); 3849 return (png_uint_16)r; 3850 # else 3851 png_int_32 lg2 = png_log16bit(value); 3852 png_fixed_point res; 3853 3854 if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0) 3855 return png_exp16bit(res); 3856 3857 /* Overflow. */ 3858 value = 0; 3859 # endif 3860 } 3861 3862 return (png_uint_16)value; 3863 } 3864 #endif /* 16BIT */ 3865 3866 /* This does the right thing based on the bit_depth field of the 3867 * png_struct, interpreting values as 8-bit or 16-bit. While the result 3868 * is nominally a 16-bit value if bit depth is 8 then the result is 3869 * 8-bit (as are the arguments.) 3870 */ 3871 png_uint_16 /* PRIVATE */ 3872 png_gamma_correct(png_structrp png_ptr, unsigned int value, 3873 png_fixed_point gamma_val) 3874 { 3875 if (png_ptr->bit_depth == 8) 3876 return png_gamma_8bit_correct(value, gamma_val); 3877 3878 #ifdef PNG_16BIT_SUPPORTED 3879 else 3880 return png_gamma_16bit_correct(value, gamma_val); 3881 #else 3882 /* should not reach this */ 3883 return 0; 3884 #endif /* 16BIT */ 3885 } 3886 3887 #ifdef PNG_16BIT_SUPPORTED 3888 /* Internal function to build a single 16-bit table - the table consists of 3889 * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount 3890 * to shift the input values right (or 16-number_of_signifiant_bits). 3891 * 3892 * The caller is responsible for ensuring that the table gets cleaned up on 3893 * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument 3894 * should be somewhere that will be cleaned. 3895 */ 3896 static void 3897 png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable, 3898 PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val) 3899 { 3900 /* Various values derived from 'shift': */ 3901 PNG_CONST unsigned int num = 1U << (8U - shift); 3902 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3903 /* CSE the division and work round wacky GCC warnings (see the comments 3904 * in png_gamma_8bit_correct for where these come from.) 3905 */ 3906 PNG_CONST double fmax = 1./(((png_int_32)1 << (16U - shift))-1); 3907 #endif 3908 PNG_CONST unsigned int max = (1U << (16U - shift))-1U; 3909 PNG_CONST unsigned int max_by_2 = 1U << (15U-shift); 3910 unsigned int i; 3911 3912 png_uint_16pp table = *ptable = 3913 (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p))); 3914 3915 for (i = 0; i < num; i++) 3916 { 3917 png_uint_16p sub_table = table[i] = 3918 (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16))); 3919 3920 /* The 'threshold' test is repeated here because it can arise for one of 3921 * the 16-bit tables even if the others don't hit it. 3922 */ 3923 if (png_gamma_significant(gamma_val) != 0) 3924 { 3925 /* The old code would overflow at the end and this would cause the 3926 * 'pow' function to return a result >1, resulting in an 3927 * arithmetic error. This code follows the spec exactly; ig is 3928 * the recovered input sample, it always has 8-16 bits. 3929 * 3930 * We want input * 65535/max, rounded, the arithmetic fits in 32 3931 * bits (unsigned) so long as max <= 32767. 3932 */ 3933 unsigned int j; 3934 for (j = 0; j < 256; j++) 3935 { 3936 png_uint_32 ig = (j << (8-shift)) + i; 3937 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED 3938 /* Inline the 'max' scaling operation: */ 3939 /* See png_gamma_8bit_correct for why the cast to (int) is 3940 * required here. 3941 */ 3942 double d = floor(65535.*pow(ig*fmax, gamma_val*.00001)+.5); 3943 sub_table[j] = (png_uint_16)d; 3944 # else 3945 if (shift != 0) 3946 ig = (ig * 65535U + max_by_2)/max; 3947 3948 sub_table[j] = png_gamma_16bit_correct(ig, gamma_val); 3949 # endif 3950 } 3951 } 3952 else 3953 { 3954 /* We must still build a table, but do it the fast way. */ 3955 unsigned int j; 3956 3957 for (j = 0; j < 256; j++) 3958 { 3959 png_uint_32 ig = (j << (8-shift)) + i; 3960 3961 if (shift != 0) 3962 ig = (ig * 65535U + max_by_2)/max; 3963 3964 sub_table[j] = (png_uint_16)ig; 3965 } 3966 } 3967 } 3968 } 3969 3970 /* NOTE: this function expects the *inverse* of the overall gamma transformation 3971 * required. 3972 */ 3973 static void 3974 png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable, 3975 PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val) 3976 { 3977 PNG_CONST unsigned int num = 1U << (8U - shift); 3978 PNG_CONST unsigned int max = (1U << (16U - shift))-1U; 3979 unsigned int i; 3980 png_uint_32 last; 3981 3982 png_uint_16pp table = *ptable = 3983 (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p))); 3984 3985 /* 'num' is the number of tables and also the number of low bits of low 3986 * bits of the input 16-bit value used to select a table. Each table is 3987 * itself indexed by the high 8 bits of the value. 3988 */ 3989 for (i = 0; i < num; i++) 3990 table[i] = (png_uint_16p)png_malloc(png_ptr, 3991 256 * (sizeof (png_uint_16))); 3992 3993 /* 'gamma_val' is set to the reciprocal of the value calculated above, so 3994 * pow(out,g) is an *input* value. 'last' is the last input value set. 3995 * 3996 * In the loop 'i' is used to find output values. Since the output is 3997 * 8-bit there are only 256 possible values. The tables are set up to 3998 * select the closest possible output value for each input by finding 3999 * the input value at the boundary between each pair of output values 4000 * and filling the table up to that boundary with the lower output 4001 * value. 4002 * 4003 * The boundary values are 0.5,1.5..253.5,254.5. Since these are 9-bit 4004 * values the code below uses a 16-bit value in i; the values start at 4005 * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last 4006 * entries are filled with 255). Start i at 128 and fill all 'last' 4007 * table entries <= 'max' 4008 */ 4009 last = 0; 4010 for (i = 0; i < 255; ++i) /* 8-bit output value */ 4011 { 4012 /* Find the corresponding maximum input value */ 4013 png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */ 4014 4015 /* Find the boundary value in 16 bits: */ 4016 png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val); 4017 4018 /* Adjust (round) to (16-shift) bits: */ 4019 bound = (bound * max + 32768U)/65535U + 1U; 4020 4021 while (last < bound) 4022 { 4023 table[last & (0xffU >> shift)][last >> (8U - shift)] = out; 4024 last++; 4025 } 4026 } 4027 4028 /* And fill in the final entries. */ 4029 while (last < (num << 8)) 4030 { 4031 table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U; 4032 last++; 4033 } 4034 } 4035 #endif /* 16BIT */ 4036 4037 /* Build a single 8-bit table: same as the 16-bit case but much simpler (and 4038 * typically much faster). Note that libpng currently does no sBIT processing 4039 * (apparently contrary to the spec) so a 256-entry table is always generated. 4040 */ 4041 static void 4042 png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable, 4043 PNG_CONST png_fixed_point gamma_val) 4044 { 4045 unsigned int i; 4046 png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256); 4047 4048 if (png_gamma_significant(gamma_val) != 0) 4049 for (i=0; i<256; i++) 4050 table[i] = png_gamma_8bit_correct(i, gamma_val); 4051 4052 else 4053 for (i=0; i<256; ++i) 4054 table[i] = (png_byte)(i & 0xff); 4055 } 4056 4057 /* Used from png_read_destroy and below to release the memory used by the gamma 4058 * tables. 4059 */ 4060 void /* PRIVATE */ 4061 png_destroy_gamma_table(png_structrp png_ptr) 4062 { 4063 png_free(png_ptr, png_ptr->gamma_table); 4064 png_ptr->gamma_table = NULL; 4065 4066 #ifdef PNG_16BIT_SUPPORTED 4067 if (png_ptr->gamma_16_table != NULL) 4068 { 4069 int i; 4070 int istop = (1 << (8 - png_ptr->gamma_shift)); 4071 for (i = 0; i < istop; i++) 4072 { 4073 png_free(png_ptr, png_ptr->gamma_16_table[i]); 4074 } 4075 png_free(png_ptr, png_ptr->gamma_16_table); 4076 png_ptr->gamma_16_table = NULL; 4077 } 4078 #endif /* 16BIT */ 4079 4080 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ 4081 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ 4082 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) 4083 png_free(png_ptr, png_ptr->gamma_from_1); 4084 png_ptr->gamma_from_1 = NULL; 4085 png_free(png_ptr, png_ptr->gamma_to_1); 4086 png_ptr->gamma_to_1 = NULL; 4087 4088 #ifdef PNG_16BIT_SUPPORTED 4089 if (png_ptr->gamma_16_from_1 != NULL) 4090 { 4091 int i; 4092 int istop = (1 << (8 - png_ptr->gamma_shift)); 4093 for (i = 0; i < istop; i++) 4094 { 4095 png_free(png_ptr, png_ptr->gamma_16_from_1[i]); 4096 } 4097 png_free(png_ptr, png_ptr->gamma_16_from_1); 4098 png_ptr->gamma_16_from_1 = NULL; 4099 } 4100 if (png_ptr->gamma_16_to_1 != NULL) 4101 { 4102 int i; 4103 int istop = (1 << (8 - png_ptr->gamma_shift)); 4104 for (i = 0; i < istop; i++) 4105 { 4106 png_free(png_ptr, png_ptr->gamma_16_to_1[i]); 4107 } 4108 png_free(png_ptr, png_ptr->gamma_16_to_1); 4109 png_ptr->gamma_16_to_1 = NULL; 4110 } 4111 #endif /* 16BIT */ 4112 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ 4113 } 4114 4115 /* We build the 8- or 16-bit gamma tables here. Note that for 16-bit 4116 * tables, we don't make a full table if we are reducing to 8-bit in 4117 * the future. Note also how the gamma_16 tables are segmented so that 4118 * we don't need to allocate > 64K chunks for a full 16-bit table. 4119 */ 4120 void /* PRIVATE */ 4121 png_build_gamma_table(png_structrp png_ptr, int bit_depth) 4122 { 4123 png_debug(1, "in png_build_gamma_table"); 4124 4125 /* Remove any existing table; this copes with multiple calls to 4126 * png_read_update_info. The warning is because building the gamma tables 4127 * multiple times is a performance hit - it's harmless but the ability to 4128 * call png_read_update_info() multiple times is new in 1.5.6 so it seems 4129 * sensible to warn if the app introduces such a hit. 4130 */ 4131 if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL) 4132 { 4133 png_warning(png_ptr, "gamma table being rebuilt"); 4134 png_destroy_gamma_table(png_ptr); 4135 } 4136 4137 if (bit_depth <= 8) 4138 { 4139 png_build_8bit_table(png_ptr, &png_ptr->gamma_table, 4140 png_ptr->screen_gamma > 0 ? 4141 png_reciprocal2(png_ptr->colorspace.gamma, 4142 png_ptr->screen_gamma) : PNG_FP_1); 4143 4144 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ 4145 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ 4146 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) 4147 if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0) 4148 { 4149 png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1, 4150 png_reciprocal(png_ptr->colorspace.gamma)); 4151 4152 png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1, 4153 png_ptr->screen_gamma > 0 ? 4154 png_reciprocal(png_ptr->screen_gamma) : 4155 png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */); 4156 } 4157 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ 4158 } 4159 #ifdef PNG_16BIT_SUPPORTED 4160 else 4161 { 4162 png_byte shift, sig_bit; 4163 4164 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0) 4165 { 4166 sig_bit = png_ptr->sig_bit.red; 4167 4168 if (png_ptr->sig_bit.green > sig_bit) 4169 sig_bit = png_ptr->sig_bit.green; 4170 4171 if (png_ptr->sig_bit.blue > sig_bit) 4172 sig_bit = png_ptr->sig_bit.blue; 4173 } 4174 else 4175 sig_bit = png_ptr->sig_bit.gray; 4176 4177 /* 16-bit gamma code uses this equation: 4178 * 4179 * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8] 4180 * 4181 * Where 'iv' is the input color value and 'ov' is the output value - 4182 * pow(iv, gamma). 4183 * 4184 * Thus the gamma table consists of up to 256 256-entry tables. The table 4185 * is selected by the (8-gamma_shift) most significant of the low 8 bits 4186 * of the color value then indexed by the upper 8 bits: 4187 * 4188 * table[low bits][high 8 bits] 4189 * 4190 * So the table 'n' corresponds to all those 'iv' of: 4191 * 4192 * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1> 4193 * 4194 */ 4195 if (sig_bit > 0 && sig_bit < 16U) 4196 /* shift == insignificant bits */ 4197 shift = (png_byte)((16U - sig_bit) & 0xff); 4198 4199 else 4200 shift = 0; /* keep all 16 bits */ 4201 4202 if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0) 4203 { 4204 /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively 4205 * the significant bits in the *input* when the output will 4206 * eventually be 8 bits. By default it is 11. 4207 */ 4208 if (shift < (16U - PNG_MAX_GAMMA_8)) 4209 shift = (16U - PNG_MAX_GAMMA_8); 4210 } 4211 4212 if (shift > 8U) 4213 shift = 8U; /* Guarantees at least one table! */ 4214 4215 png_ptr->gamma_shift = shift; 4216 4217 /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now 4218 * PNG_COMPOSE). This effectively smashed the background calculation for 4219 * 16-bit output because the 8-bit table assumes the result will be 4220 * reduced to 8 bits. 4221 */ 4222 if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0) 4223 png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift, 4224 png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma, 4225 png_ptr->screen_gamma) : PNG_FP_1); 4226 4227 else 4228 png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift, 4229 png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma, 4230 png_ptr->screen_gamma) : PNG_FP_1); 4231 4232 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ 4233 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ 4234 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) 4235 if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0) 4236 { 4237 png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift, 4238 png_reciprocal(png_ptr->colorspace.gamma)); 4239 4240 /* Notice that the '16 from 1' table should be full precision, however 4241 * the lookup on this table still uses gamma_shift, so it can't be. 4242 * TODO: fix this. 4243 */ 4244 png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift, 4245 png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) : 4246 png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */); 4247 } 4248 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ 4249 } 4250 #endif /* 16BIT */ 4251 } 4252 #endif /* READ_GAMMA */ 4253 4254 /* HARDWARE OR SOFTWARE OPTION SUPPORT */ 4255 #ifdef PNG_SET_OPTION_SUPPORTED 4256 int PNGAPI 4257 png_set_option(png_structrp png_ptr, int option, int onoff) 4258 { 4259 if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT && 4260 (option & 1) == 0) 4261 { 4262 int mask = 3 << option; 4263 int setting = (2 + (onoff != 0)) << option; 4264 int current = png_ptr->options; 4265 4266 png_ptr->options = (png_byte)(((current & ~mask) | setting) & 0xff); 4267 4268 return (current & mask) >> option; 4269 } 4270 4271 return PNG_OPTION_INVALID; 4272 } 4273 #endif 4274 4275 /* sRGB support */ 4276 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\ 4277 defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) 4278 /* sRGB conversion tables; these are machine generated with the code in 4279 * contrib/tools/makesRGB.c. The actual sRGB transfer curve defined in the 4280 * specification (see the article at http://en.wikipedia.org/wiki/SRGB) 4281 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng. 4282 * The sRGB to linear table is exact (to the nearest 16-bit linear fraction). 4283 * The inverse (linear to sRGB) table has accuracies as follows: 4284 * 4285 * For all possible (255*65535+1) input values: 4286 * 4287 * error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact 4288 * 4289 * For the input values corresponding to the 65536 16-bit values: 4290 * 4291 * error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact 4292 * 4293 * In all cases the inexact readings are only off by one. 4294 */ 4295 4296 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED 4297 /* The convert-to-sRGB table is only currently required for read. */ 4298 const png_uint_16 png_sRGB_table[256] = 4299 { 4300 0,20,40,60,80,99,119,139, 4301 159,179,199,219,241,264,288,313, 4302 340,367,396,427,458,491,526,562, 4303 599,637,677,718,761,805,851,898, 4304 947,997,1048,1101,1156,1212,1270,1330, 4305 1391,1453,1517,1583,1651,1720,1790,1863, 4306 1937,2013,2090,2170,2250,2333,2418,2504, 4307 2592,2681,2773,2866,2961,3058,3157,3258, 4308 3360,3464,3570,3678,3788,3900,4014,4129, 4309 4247,4366,4488,4611,4736,4864,4993,5124, 4310 5257,5392,5530,5669,5810,5953,6099,6246, 4311 6395,6547,6700,6856,7014,7174,7335,7500, 4312 7666,7834,8004,8177,8352,8528,8708,8889, 4313 9072,9258,9445,9635,9828,10022,10219,10417, 4314 10619,10822,11028,11235,11446,11658,11873,12090, 4315 12309,12530,12754,12980,13209,13440,13673,13909, 4316 14146,14387,14629,14874,15122,15371,15623,15878, 4317 16135,16394,16656,16920,17187,17456,17727,18001, 4318 18277,18556,18837,19121,19407,19696,19987,20281, 4319 20577,20876,21177,21481,21787,22096,22407,22721, 4320 23038,23357,23678,24002,24329,24658,24990,25325, 4321 25662,26001,26344,26688,27036,27386,27739,28094, 4322 28452,28813,29176,29542,29911,30282,30656,31033, 4323 31412,31794,32179,32567,32957,33350,33745,34143, 4324 34544,34948,35355,35764,36176,36591,37008,37429, 4325 37852,38278,38706,39138,39572,40009,40449,40891, 4326 41337,41785,42236,42690,43147,43606,44069,44534, 4327 45002,45473,45947,46423,46903,47385,47871,48359, 4328 48850,49344,49841,50341,50844,51349,51858,52369, 4329 52884,53401,53921,54445,54971,55500,56032,56567, 4330 57105,57646,58190,58737,59287,59840,60396,60955, 4331 61517,62082,62650,63221,63795,64372,64952,65535 4332 }; 4333 #endif /* SIMPLIFIED_READ */ 4334 4335 /* The base/delta tables are required for both read and write (but currently 4336 * only the simplified versions.) 4337 */ 4338 const png_uint_16 png_sRGB_base[512] = 4339 { 4340 128,1782,3383,4644,5675,6564,7357,8074, 4341 8732,9346,9921,10463,10977,11466,11935,12384, 4342 12816,13233,13634,14024,14402,14769,15125,15473, 4343 15812,16142,16466,16781,17090,17393,17690,17981, 4344 18266,18546,18822,19093,19359,19621,19879,20133, 4345 20383,20630,20873,21113,21349,21583,21813,22041, 4346 22265,22487,22707,22923,23138,23350,23559,23767, 4347 23972,24175,24376,24575,24772,24967,25160,25352, 4348 25542,25730,25916,26101,26284,26465,26645,26823, 4349 27000,27176,27350,27523,27695,27865,28034,28201, 4350 28368,28533,28697,28860,29021,29182,29341,29500, 4351 29657,29813,29969,30123,30276,30429,30580,30730, 4352 30880,31028,31176,31323,31469,31614,31758,31902, 4353 32045,32186,32327,32468,32607,32746,32884,33021, 4354 33158,33294,33429,33564,33697,33831,33963,34095, 4355 34226,34357,34486,34616,34744,34873,35000,35127, 4356 35253,35379,35504,35629,35753,35876,35999,36122, 4357 36244,36365,36486,36606,36726,36845,36964,37083, 4358 37201,37318,37435,37551,37668,37783,37898,38013, 4359 38127,38241,38354,38467,38580,38692,38803,38915, 4360 39026,39136,39246,39356,39465,39574,39682,39790, 4361 39898,40005,40112,40219,40325,40431,40537,40642, 4362 40747,40851,40955,41059,41163,41266,41369,41471, 4363 41573,41675,41777,41878,41979,42079,42179,42279, 4364 42379,42478,42577,42676,42775,42873,42971,43068, 4365 43165,43262,43359,43456,43552,43648,43743,43839, 4366 43934,44028,44123,44217,44311,44405,44499,44592, 4367 44685,44778,44870,44962,45054,45146,45238,45329, 4368 45420,45511,45601,45692,45782,45872,45961,46051, 4369 46140,46229,46318,46406,46494,46583,46670,46758, 4370 46846,46933,47020,47107,47193,47280,47366,47452, 4371 47538,47623,47709,47794,47879,47964,48048,48133, 4372 48217,48301,48385,48468,48552,48635,48718,48801, 4373 48884,48966,49048,49131,49213,49294,49376,49458, 4374 49539,49620,49701,49782,49862,49943,50023,50103, 4375 50183,50263,50342,50422,50501,50580,50659,50738, 4376 50816,50895,50973,51051,51129,51207,51285,51362, 4377 51439,51517,51594,51671,51747,51824,51900,51977, 4378 52053,52129,52205,52280,52356,52432,52507,52582, 4379 52657,52732,52807,52881,52956,53030,53104,53178, 4380 53252,53326,53400,53473,53546,53620,53693,53766, 4381 53839,53911,53984,54056,54129,54201,54273,54345, 4382 54417,54489,54560,54632,54703,54774,54845,54916, 4383 54987,55058,55129,55199,55269,55340,55410,55480, 4384 55550,55620,55689,55759,55828,55898,55967,56036, 4385 56105,56174,56243,56311,56380,56448,56517,56585, 4386 56653,56721,56789,56857,56924,56992,57059,57127, 4387 57194,57261,57328,57395,57462,57529,57595,57662, 4388 57728,57795,57861,57927,57993,58059,58125,58191, 4389 58256,58322,58387,58453,58518,58583,58648,58713, 4390 58778,58843,58908,58972,59037,59101,59165,59230, 4391 59294,59358,59422,59486,59549,59613,59677,59740, 4392 59804,59867,59930,59993,60056,60119,60182,60245, 4393 60308,60370,60433,60495,60558,60620,60682,60744, 4394 60806,60868,60930,60992,61054,61115,61177,61238, 4395 61300,61361,61422,61483,61544,61605,61666,61727, 4396 61788,61848,61909,61969,62030,62090,62150,62211, 4397 62271,62331,62391,62450,62510,62570,62630,62689, 4398 62749,62808,62867,62927,62986,63045,63104,63163, 4399 63222,63281,63340,63398,63457,63515,63574,63632, 4400 63691,63749,63807,63865,63923,63981,64039,64097, 4401 64155,64212,64270,64328,64385,64443,64500,64557, 4402 64614,64672,64729,64786,64843,64900,64956,65013, 4403 65070,65126,65183,65239,65296,65352,65409,65465 4404 }; 4405 4406 const png_byte png_sRGB_delta[512] = 4407 { 4408 207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54, 4409 52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36, 4410 35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28, 4411 28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24, 4412 23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21, 4413 21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19, 4414 19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17, 4415 17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16, 4416 16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15, 4417 15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14, 4418 14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13, 4419 13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12, 4420 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12, 4421 12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11, 4422 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11, 4423 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11, 4424 11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 4425 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 4426 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 4427 10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 4428 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 4429 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 4430 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 4431 9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 4432 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 4433 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 4434 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 4435 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 4436 8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7, 4437 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 4438 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 4439 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 4440 }; 4441 #endif /* SIMPLIFIED READ/WRITE sRGB support */ 4442 4443 /* SIMPLIFIED READ/WRITE SUPPORT */ 4444 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\ 4445 defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) 4446 static int 4447 png_image_free_function(png_voidp argument) 4448 { 4449 png_imagep image = png_voidcast(png_imagep, argument); 4450 png_controlp cp = image->opaque; 4451 png_control c; 4452 4453 /* Double check that we have a png_ptr - it should be impossible to get here 4454 * without one. 4455 */ 4456 if (cp->png_ptr == NULL) 4457 return 0; 4458 4459 /* First free any data held in the control structure. */ 4460 # ifdef PNG_STDIO_SUPPORTED 4461 if (cp->owned_file != 0) 4462 { 4463 FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr); 4464 cp->owned_file = 0; 4465 4466 /* Ignore errors here. */ 4467 if (fp != NULL) 4468 { 4469 cp->png_ptr->io_ptr = NULL; 4470 (void)fclose(fp); 4471 } 4472 } 4473 # endif 4474 4475 /* Copy the control structure so that the original, allocated, version can be 4476 * safely freed. Notice that a png_error here stops the remainder of the 4477 * cleanup, but this is probably fine because that would indicate bad memory 4478 * problems anyway. 4479 */ 4480 c = *cp; 4481 image->opaque = &c; 4482 png_free(c.png_ptr, cp); 4483 4484 /* Then the structures, calling the correct API. */ 4485 if (c.for_write != 0) 4486 { 4487 # ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED 4488 png_destroy_write_struct(&c.png_ptr, &c.info_ptr); 4489 # else 4490 png_error(c.png_ptr, "simplified write not supported"); 4491 # endif 4492 } 4493 else 4494 { 4495 # ifdef PNG_SIMPLIFIED_READ_SUPPORTED 4496 png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL); 4497 # else 4498 png_error(c.png_ptr, "simplified read not supported"); 4499 # endif 4500 } 4501 4502 /* Success. */ 4503 return 1; 4504 } 4505 4506 void PNGAPI 4507 png_image_free(png_imagep image) 4508 { 4509 /* Safely call the real function, but only if doing so is safe at this point 4510 * (if not inside an error handling context). Otherwise assume 4511 * png_safe_execute will call this API after the return. 4512 */ 4513 if (image != NULL && image->opaque != NULL && 4514 image->opaque->error_buf == NULL) 4515 { 4516 /* Ignore errors here: */ 4517 (void)png_safe_execute(image, png_image_free_function, image); 4518 image->opaque = NULL; 4519 } 4520 } 4521 4522 int /* PRIVATE */ 4523 png_image_error(png_imagep image, png_const_charp error_message) 4524 { 4525 /* Utility to log an error. */ 4526 png_safecat(image->message, (sizeof image->message), 0, error_message); 4527 image->warning_or_error |= PNG_IMAGE_ERROR; 4528 png_image_free(image); 4529 return 0; 4530 } 4531 4532 #endif /* SIMPLIFIED READ/WRITE */ 4533 #endif /* READ || WRITE */ 4534