1 2 /* pngread.c - read a PNG file 3 * 4 * Last changed in libpng 1.6.10 [March 6, 2014] 5 * Copyright (c) 1998-2014 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 * This file contains routines that an application calls directly to 14 * read a PNG file or stream. 15 */ 16 17 #include "pngpriv.h" 18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED) 19 # include <errno.h> 20 #endif 21 22 #ifdef PNG_READ_SUPPORTED 23 24 /* Create a PNG structure for reading, and allocate any memory needed. */ 25 PNG_FUNCTION(png_structp,PNGAPI 26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr, 27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED) 28 { 29 #ifndef PNG_USER_MEM_SUPPORTED 30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr, 31 error_fn, warn_fn, NULL, NULL, NULL); 32 #else 33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn, 34 warn_fn, NULL, NULL, NULL); 35 } 36 37 /* Alternate create PNG structure for reading, and allocate any memory 38 * needed. 39 */ 40 PNG_FUNCTION(png_structp,PNGAPI 41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr, 42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr, 43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED) 44 { 45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr, 46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn); 47 #endif /* PNG_USER_MEM_SUPPORTED */ 48 49 if (png_ptr != NULL) 50 { 51 png_ptr->mode = PNG_IS_READ_STRUCT; 52 53 /* Added in libpng-1.6.0; this can be used to detect a read structure if 54 * required (it will be zero in a write structure.) 55 */ 56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED 57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE; 58 # endif 59 60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED 61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN; 62 63 /* In stable builds only warn if an application error can be completely 64 * handled. 65 */ 66 # if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC 67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN; 68 # endif 69 # endif 70 71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't 72 * do it itself) avoiding setting the default function if it is not 73 * required. 74 */ 75 png_set_read_fn(png_ptr, NULL, NULL); 76 77 #ifdef PNG_INDEX_SUPPORTED 78 png_ptr->index = NULL; 79 #endif 80 } 81 82 return png_ptr; 83 } 84 85 86 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 87 /* Read the information before the actual image data. This has been 88 * changed in v0.90 to allow reading a file that already has the magic 89 * bytes read from the stream. You can tell libpng how many bytes have 90 * been read from the beginning of the stream (up to the maximum of 8) 91 * via png_set_sig_bytes(), and we will only check the remaining bytes 92 * here. The application can then have access to the signature bytes we 93 * read if it is determined that this isn't a valid PNG file. 94 */ 95 void PNGAPI 96 png_read_info(png_structrp png_ptr, png_inforp info_ptr) 97 { 98 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 99 int keep; 100 #endif 101 102 png_debug(1, "in png_read_info"); 103 104 if (png_ptr == NULL || info_ptr == NULL) 105 return; 106 107 /* Read and check the PNG file signature. */ 108 png_read_sig(png_ptr, info_ptr); 109 110 for (;;) 111 { 112 png_uint_32 length = png_read_chunk_header(png_ptr); 113 png_uint_32 chunk_name = png_ptr->chunk_name; 114 115 /* IDAT logic needs to happen here to simplify getting the two flags 116 * right. 117 */ 118 if (chunk_name == png_IDAT) 119 { 120 if (!(png_ptr->mode & PNG_HAVE_IHDR)) 121 png_chunk_error(png_ptr, "Missing IHDR before IDAT"); 122 123 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE && 124 !(png_ptr->mode & PNG_HAVE_PLTE)) 125 png_chunk_error(png_ptr, "Missing PLTE before IDAT"); 126 127 else if (png_ptr->mode & PNG_AFTER_IDAT) 128 png_chunk_benign_error(png_ptr, "Too many IDATs found"); 129 130 png_ptr->mode |= PNG_HAVE_IDAT; 131 } 132 133 else if (png_ptr->mode & PNG_HAVE_IDAT) 134 png_ptr->mode |= PNG_AFTER_IDAT; 135 136 /* This should be a binary subdivision search or a hash for 137 * matching the chunk name rather than a linear search. 138 */ 139 if (chunk_name == png_IHDR) 140 png_handle_IHDR(png_ptr, info_ptr, length); 141 142 else if (chunk_name == png_IEND) 143 png_handle_IEND(png_ptr, info_ptr, length); 144 145 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 146 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0) 147 { 148 png_handle_unknown(png_ptr, info_ptr, length, keep); 149 150 if (chunk_name == png_PLTE) 151 png_ptr->mode |= PNG_HAVE_PLTE; 152 153 else if (chunk_name == png_IDAT) 154 { 155 png_ptr->idat_size = 0; /* It has been consumed */ 156 break; 157 } 158 } 159 #endif 160 else if (chunk_name == png_PLTE) 161 png_handle_PLTE(png_ptr, info_ptr, length); 162 163 else if (chunk_name == png_IDAT) 164 { 165 png_ptr->idat_size = length; 166 break; 167 } 168 169 #ifdef PNG_READ_bKGD_SUPPORTED 170 else if (chunk_name == png_bKGD) 171 png_handle_bKGD(png_ptr, info_ptr, length); 172 #endif 173 174 #ifdef PNG_READ_cHRM_SUPPORTED 175 else if (chunk_name == png_cHRM) 176 png_handle_cHRM(png_ptr, info_ptr, length); 177 #endif 178 179 #ifdef PNG_READ_gAMA_SUPPORTED 180 else if (chunk_name == png_gAMA) 181 png_handle_gAMA(png_ptr, info_ptr, length); 182 #endif 183 184 #ifdef PNG_READ_hIST_SUPPORTED 185 else if (chunk_name == png_hIST) 186 png_handle_hIST(png_ptr, info_ptr, length); 187 #endif 188 189 #ifdef PNG_READ_oFFs_SUPPORTED 190 else if (chunk_name == png_oFFs) 191 png_handle_oFFs(png_ptr, info_ptr, length); 192 #endif 193 194 #ifdef PNG_READ_pCAL_SUPPORTED 195 else if (chunk_name == png_pCAL) 196 png_handle_pCAL(png_ptr, info_ptr, length); 197 #endif 198 199 #ifdef PNG_READ_sCAL_SUPPORTED 200 else if (chunk_name == png_sCAL) 201 png_handle_sCAL(png_ptr, info_ptr, length); 202 #endif 203 204 #ifdef PNG_READ_pHYs_SUPPORTED 205 else if (chunk_name == png_pHYs) 206 png_handle_pHYs(png_ptr, info_ptr, length); 207 #endif 208 209 #ifdef PNG_READ_sBIT_SUPPORTED 210 else if (chunk_name == png_sBIT) 211 png_handle_sBIT(png_ptr, info_ptr, length); 212 #endif 213 214 #ifdef PNG_READ_sRGB_SUPPORTED 215 else if (chunk_name == png_sRGB) 216 png_handle_sRGB(png_ptr, info_ptr, length); 217 #endif 218 219 #ifdef PNG_READ_iCCP_SUPPORTED 220 else if (chunk_name == png_iCCP) 221 png_handle_iCCP(png_ptr, info_ptr, length); 222 #endif 223 224 #ifdef PNG_READ_sPLT_SUPPORTED 225 else if (chunk_name == png_sPLT) 226 png_handle_sPLT(png_ptr, info_ptr, length); 227 #endif 228 229 #ifdef PNG_READ_tEXt_SUPPORTED 230 else if (chunk_name == png_tEXt) 231 png_handle_tEXt(png_ptr, info_ptr, length); 232 #endif 233 234 #ifdef PNG_READ_tIME_SUPPORTED 235 else if (chunk_name == png_tIME) 236 png_handle_tIME(png_ptr, info_ptr, length); 237 #endif 238 239 #ifdef PNG_READ_tRNS_SUPPORTED 240 else if (chunk_name == png_tRNS) 241 png_handle_tRNS(png_ptr, info_ptr, length); 242 #endif 243 244 #ifdef PNG_READ_zTXt_SUPPORTED 245 else if (chunk_name == png_zTXt) 246 png_handle_zTXt(png_ptr, info_ptr, length); 247 #endif 248 249 #ifdef PNG_READ_iTXt_SUPPORTED 250 else if (chunk_name == png_iTXt) 251 png_handle_iTXt(png_ptr, info_ptr, length); 252 #endif 253 254 else 255 png_handle_unknown(png_ptr, info_ptr, length, 256 PNG_HANDLE_CHUNK_AS_DEFAULT); 257 } 258 } 259 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 260 261 /* Optional call to update the users info_ptr structure */ 262 void PNGAPI 263 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr) 264 { 265 png_debug(1, "in png_read_update_info"); 266 267 if (png_ptr != NULL) 268 { 269 #ifdef PNG_INDEX_SUPPORTED 270 if (png_ptr->index) { 271 png_read_start_row(png_ptr); 272 } 273 #endif 274 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 275 { 276 png_read_start_row(png_ptr); 277 278 # ifdef PNG_READ_TRANSFORMS_SUPPORTED 279 png_read_transform_info(png_ptr, info_ptr); 280 # else 281 PNG_UNUSED(info_ptr) 282 # endif 283 } 284 #ifndef PNG_INDEX_SUPPORTED 285 /* New in 1.6.0 this avoids the bug of doing the initializations twice */ 286 else 287 png_app_error(png_ptr, 288 "png_read_update_info/png_start_read_image: duplicate call"); 289 #endif 290 } 291 } 292 293 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 294 /* Initialize palette, background, etc, after transformations 295 * are set, but before any reading takes place. This allows 296 * the user to obtain a gamma-corrected palette, for example. 297 * If the user doesn't call this, we will do it ourselves. 298 */ 299 void PNGAPI 300 png_start_read_image(png_structrp png_ptr) 301 { 302 png_debug(1, "in png_start_read_image"); 303 304 if (png_ptr != NULL) 305 { 306 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0) 307 png_read_start_row(png_ptr); 308 309 /* New in 1.6.0 this avoids the bug of doing the initializations twice */ 310 else 311 png_app_error(png_ptr, 312 "png_start_read_image/png_read_update_info: duplicate call"); 313 } 314 } 315 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 316 317 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 318 #ifdef PNG_MNG_FEATURES_SUPPORTED 319 /* Undoes intrapixel differencing, 320 * NOTE: this is apparently only supported in the 'sequential' reader. 321 */ 322 static void 323 png_do_read_intrapixel(png_row_infop row_info, png_bytep row) 324 { 325 png_debug(1, "in png_do_read_intrapixel"); 326 327 if ( 328 (row_info->color_type & PNG_COLOR_MASK_COLOR)) 329 { 330 int bytes_per_pixel; 331 png_uint_32 row_width = row_info->width; 332 333 if (row_info->bit_depth == 8) 334 { 335 png_bytep rp; 336 png_uint_32 i; 337 338 if (row_info->color_type == PNG_COLOR_TYPE_RGB) 339 bytes_per_pixel = 3; 340 341 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA) 342 bytes_per_pixel = 4; 343 344 else 345 return; 346 347 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel) 348 { 349 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff); 350 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff); 351 } 352 } 353 else if (row_info->bit_depth == 16) 354 { 355 png_bytep rp; 356 png_uint_32 i; 357 358 if (row_info->color_type == PNG_COLOR_TYPE_RGB) 359 bytes_per_pixel = 6; 360 361 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA) 362 bytes_per_pixel = 8; 363 364 else 365 return; 366 367 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel) 368 { 369 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1); 370 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3); 371 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5); 372 png_uint_32 red = (s0 + s1 + 65536) & 0xffff; 373 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff; 374 *(rp ) = (png_byte)((red >> 8) & 0xff); 375 *(rp + 1) = (png_byte)(red & 0xff); 376 *(rp + 4) = (png_byte)((blue >> 8) & 0xff); 377 *(rp + 5) = (png_byte)(blue & 0xff); 378 } 379 } 380 } 381 } 382 #endif /* PNG_MNG_FEATURES_SUPPORTED */ 383 384 void PNGAPI 385 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row) 386 { 387 png_row_info row_info; 388 389 if (png_ptr == NULL) 390 return; 391 392 png_debug2(1, "in png_read_row (row %lu, pass %d)", 393 (unsigned long)png_ptr->row_number, png_ptr->pass); 394 395 /* png_read_start_row sets the information (in particular iwidth) for this 396 * interlace pass. 397 */ 398 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT)) 399 png_read_start_row(png_ptr); 400 401 /* 1.5.6: row_info moved out of png_struct to a local here. */ 402 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */ 403 row_info.color_type = png_ptr->color_type; 404 row_info.bit_depth = png_ptr->bit_depth; 405 row_info.channels = png_ptr->channels; 406 row_info.pixel_depth = png_ptr->pixel_depth; 407 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width); 408 409 if (png_ptr->row_number == 0 && png_ptr->pass == 0) 410 { 411 /* Check for transforms that have been set but were defined out */ 412 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED) 413 if (png_ptr->transformations & PNG_INVERT_MONO) 414 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined"); 415 #endif 416 417 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED) 418 if (png_ptr->transformations & PNG_FILLER) 419 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined"); 420 #endif 421 422 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \ 423 !defined(PNG_READ_PACKSWAP_SUPPORTED) 424 if (png_ptr->transformations & PNG_PACKSWAP) 425 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined"); 426 #endif 427 428 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED) 429 if (png_ptr->transformations & PNG_PACK) 430 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined"); 431 #endif 432 433 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) 434 if (png_ptr->transformations & PNG_SHIFT) 435 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined"); 436 #endif 437 438 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED) 439 if (png_ptr->transformations & PNG_BGR) 440 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined"); 441 #endif 442 443 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED) 444 if (png_ptr->transformations & PNG_SWAP_BYTES) 445 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined"); 446 #endif 447 } 448 449 #ifdef PNG_READ_INTERLACING_SUPPORTED 450 /* If interlaced and we do not need a new row, combine row and return. 451 * Notice that the pixels we have from previous rows have been transformed 452 * already; we can only combine like with like (transformed or 453 * untransformed) and, because of the libpng API for interlaced images, this 454 * means we must transform before de-interlacing. 455 */ 456 if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE)) 457 { 458 switch (png_ptr->pass) 459 { 460 case 0: 461 if (png_ptr->row_number & 0x07) 462 { 463 if (dsp_row != NULL) 464 png_combine_row(png_ptr, dsp_row, 1/*display*/); 465 png_read_finish_row(png_ptr); 466 return; 467 } 468 break; 469 470 case 1: 471 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5) 472 { 473 if (dsp_row != NULL) 474 png_combine_row(png_ptr, dsp_row, 1/*display*/); 475 476 png_read_finish_row(png_ptr); 477 return; 478 } 479 break; 480 481 case 2: 482 if ((png_ptr->row_number & 0x07) != 4) 483 { 484 if (dsp_row != NULL && (png_ptr->row_number & 4)) 485 png_combine_row(png_ptr, dsp_row, 1/*display*/); 486 487 png_read_finish_row(png_ptr); 488 return; 489 } 490 break; 491 492 case 3: 493 if ((png_ptr->row_number & 3) || png_ptr->width < 3) 494 { 495 if (dsp_row != NULL) 496 png_combine_row(png_ptr, dsp_row, 1/*display*/); 497 498 png_read_finish_row(png_ptr); 499 return; 500 } 501 break; 502 503 case 4: 504 if ((png_ptr->row_number & 3) != 2) 505 { 506 if (dsp_row != NULL && (png_ptr->row_number & 2)) 507 png_combine_row(png_ptr, dsp_row, 1/*display*/); 508 509 png_read_finish_row(png_ptr); 510 return; 511 } 512 break; 513 514 case 5: 515 if ((png_ptr->row_number & 1) || png_ptr->width < 2) 516 { 517 if (dsp_row != NULL) 518 png_combine_row(png_ptr, dsp_row, 1/*display*/); 519 520 png_read_finish_row(png_ptr); 521 return; 522 } 523 break; 524 525 default: 526 case 6: 527 if (!(png_ptr->row_number & 1)) 528 { 529 png_read_finish_row(png_ptr); 530 return; 531 } 532 break; 533 } 534 } 535 #endif 536 537 if (!(png_ptr->mode & PNG_HAVE_IDAT)) 538 png_error(png_ptr, "Invalid attempt to read row data"); 539 540 /* Fill the row with IDAT data: */ 541 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1); 542 543 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE) 544 { 545 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST) 546 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1, 547 png_ptr->prev_row + 1, png_ptr->row_buf[0]); 548 else 549 png_error(png_ptr, "bad adaptive filter value"); 550 } 551 552 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before 553 * 1.5.6, while the buffer really is this big in current versions of libpng 554 * it may not be in the future, so this was changed just to copy the 555 * interlaced count: 556 */ 557 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1); 558 559 #ifdef PNG_MNG_FEATURES_SUPPORTED 560 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) && 561 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING)) 562 { 563 /* Intrapixel differencing */ 564 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1); 565 } 566 #endif 567 568 #ifdef PNG_READ_TRANSFORMS_SUPPORTED 569 if (png_ptr->transformations) 570 png_do_read_transformations(png_ptr, &row_info); 571 #endif 572 573 /* The transformed pixel depth should match the depth now in row_info. */ 574 if (png_ptr->transformed_pixel_depth == 0) 575 { 576 png_ptr->transformed_pixel_depth = row_info.pixel_depth; 577 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth) 578 png_error(png_ptr, "sequential row overflow"); 579 } 580 581 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth) 582 png_error(png_ptr, "internal sequential row size calculation error"); 583 584 #ifdef PNG_READ_INTERLACING_SUPPORTED 585 /* Blow up interlaced rows to full size */ 586 if (png_ptr->interlaced && 587 (png_ptr->transformations & PNG_INTERLACE)) 588 { 589 if (png_ptr->pass < 6) 590 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass, 591 png_ptr->transformations); 592 593 if (dsp_row != NULL) 594 png_combine_row(png_ptr, dsp_row, 1/*display*/); 595 596 if (row != NULL) 597 png_combine_row(png_ptr, row, 0/*row*/); 598 } 599 600 else 601 #endif 602 { 603 if (row != NULL) 604 png_combine_row(png_ptr, row, -1/*ignored*/); 605 606 if (dsp_row != NULL) 607 png_combine_row(png_ptr, dsp_row, -1/*ignored*/); 608 } 609 png_read_finish_row(png_ptr); 610 611 if (png_ptr->read_row_fn != NULL) 612 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass); 613 614 } 615 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 616 617 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 618 /* Read one or more rows of image data. If the image is interlaced, 619 * and png_set_interlace_handling() has been called, the rows need to 620 * contain the contents of the rows from the previous pass. If the 621 * image has alpha or transparency, and png_handle_alpha()[*] has been 622 * called, the rows contents must be initialized to the contents of the 623 * screen. 624 * 625 * "row" holds the actual image, and pixels are placed in it 626 * as they arrive. If the image is displayed after each pass, it will 627 * appear to "sparkle" in. "display_row" can be used to display a 628 * "chunky" progressive image, with finer detail added as it becomes 629 * available. If you do not want this "chunky" display, you may pass 630 * NULL for display_row. If you do not want the sparkle display, and 631 * you have not called png_handle_alpha(), you may pass NULL for rows. 632 * If you have called png_handle_alpha(), and the image has either an 633 * alpha channel or a transparency chunk, you must provide a buffer for 634 * rows. In this case, you do not have to provide a display_row buffer 635 * also, but you may. If the image is not interlaced, or if you have 636 * not called png_set_interlace_handling(), the display_row buffer will 637 * be ignored, so pass NULL to it. 638 * 639 * [*] png_handle_alpha() does not exist yet, as of this version of libpng 640 */ 641 642 void PNGAPI 643 png_read_rows(png_structrp png_ptr, png_bytepp row, 644 png_bytepp display_row, png_uint_32 num_rows) 645 { 646 png_uint_32 i; 647 png_bytepp rp; 648 png_bytepp dp; 649 650 png_debug(1, "in png_read_rows"); 651 652 if (png_ptr == NULL) 653 return; 654 655 rp = row; 656 dp = display_row; 657 if (rp != NULL && dp != NULL) 658 for (i = 0; i < num_rows; i++) 659 { 660 png_bytep rptr = *rp++; 661 png_bytep dptr = *dp++; 662 663 png_read_row(png_ptr, rptr, dptr); 664 } 665 666 else if (rp != NULL) 667 for (i = 0; i < num_rows; i++) 668 { 669 png_bytep rptr = *rp; 670 png_read_row(png_ptr, rptr, NULL); 671 rp++; 672 } 673 674 else if (dp != NULL) 675 for (i = 0; i < num_rows; i++) 676 { 677 png_bytep dptr = *dp; 678 png_read_row(png_ptr, NULL, dptr); 679 dp++; 680 } 681 } 682 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 683 684 #ifdef PNG_INDEX_SUPPORTED 685 #define IDAT_HEADER_SIZE 8 686 687 /* Set the png read position to a new position based on idat_position and 688 * offset. 689 */ 690 void 691 png_set_read_offset(png_structp png_ptr, 692 png_uint_32 idat_position, png_uint_32 bytes_left) 693 { 694 png_seek_data(png_ptr, idat_position); 695 png_ptr->idat_size = png_read_chunk_header(png_ptr); 696 697 // We need to add back IDAT_HEADER_SIZE because in zlib's perspective, 698 // IDAT_HEADER in PNG is already stripped out. 699 png_seek_data(png_ptr, idat_position + IDAT_HEADER_SIZE + png_ptr->idat_size - bytes_left); 700 png_ptr->idat_size = bytes_left; 701 } 702 703 /* Configure png decoder to decode the pass starting from *row. 704 * The requested row may be adjusted to align with an indexing row. 705 * The actual row for the decoder to start its decoding will be returned in 706 * *row. 707 */ 708 void PNGAPI 709 png_configure_decoder(png_structp png_ptr, int *row, int pass) 710 { 711 png_indexp index = png_ptr->index; 712 int n = *row / index->step[pass]; 713 png_line_indexp line_index = index->pass_line_index[pass][n]; 714 715 // Adjust row to an indexing row. 716 *row = n * index->step[pass]; 717 png_ptr->row_number = *row; 718 719 #ifdef PNG_READ_INTERLACING_SUPPORTED 720 if (png_ptr->interlaced) 721 png_set_interlaced_pass(png_ptr, pass); 722 #endif 723 724 long row_byte_length = 725 PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1; 726 727 inflateEnd(&png_ptr->zstream); 728 inflateCopy(&png_ptr->zstream, line_index->z_state); 729 730 // Set the png read position to line_index. 731 png_set_read_offset(png_ptr, line_index->stream_idat_position, 732 line_index->bytes_left_in_idat); 733 memcpy(png_ptr->prev_row, line_index->prev_row, row_byte_length); 734 png_ptr->zstream.avail_in = 0; 735 } 736 737 /* Build the line index and store the index in png_ptr->index. 738 */ 739 void PNGAPI 740 png_build_index(png_structp png_ptr) 741 { 742 // number of rows in a 8x8 block for each interlaced pass. 743 int number_rows_in_pass[7] = {1, 1, 1, 2, 2, 4, 4}; 744 745 int ret; 746 png_uint_32 i, j; 747 png_bytep rp; 748 int p, pass_number = 1; 749 750 #ifdef PNG_READ_INTERLACING_SUPPORTED 751 pass_number = png_set_interlace_handling(png_ptr); 752 #endif 753 754 if (png_ptr == NULL) 755 return; 756 757 png_read_start_row(png_ptr); 758 759 #ifdef PNG_READ_INTERLACING_SUPPORTED 760 if (!png_ptr->interlaced) 761 #endif 762 { 763 number_rows_in_pass[0] = 8; 764 } 765 766 rp = png_malloc(png_ptr, png_ptr->rowbytes); 767 768 png_indexp index = png_malloc(png_ptr, sizeof(png_index)); 769 png_ptr->index = index; 770 771 index->stream_idat_position = png_ptr->total_data_read - IDAT_HEADER_SIZE; 772 773 // Set the default size of index in each pass to 0, 774 // so that we can free index correctly in png_destroy_read_struct. 775 for (p = 0; p < 7; p++) 776 index->size[p] = 0; 777 778 for (p = 0; p < pass_number; p++) 779 { 780 // We adjust the index step in each pass to make sure each pass 781 // has roughly the same size of index. 782 // This way, we won't consume to much memory in recording index. 783 index->step[p] = INDEX_SAMPLE_SIZE * (8 / number_rows_in_pass[p]); 784 const int temp_size = 785 (png_ptr->height + index->step[p] - 1) / index->step[p]; 786 index->pass_line_index[p] = 787 png_malloc(png_ptr, temp_size * sizeof(png_line_indexp)); 788 789 // Get the row_byte_length seen by the filter. This value may be 790 // different from the row_byte_length of a bitmap in the case of 791 // color palette mode. 792 int row_byte_length = 793 PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1; 794 795 // Now, we record index for each indexing row. 796 for (i = 0; i < temp_size; i++) 797 { 798 png_line_indexp line_index = png_malloc(png_ptr, sizeof(png_line_index)); 799 index->pass_line_index[p][i] = line_index; 800 801 line_index->z_state = png_malloc(png_ptr, sizeof(z_stream)); 802 inflateCopy(line_index->z_state, &png_ptr->zstream); 803 line_index->prev_row = png_malloc(png_ptr, row_byte_length); 804 memcpy(line_index->prev_row, png_ptr->prev_row, row_byte_length); 805 line_index->stream_idat_position = index->stream_idat_position; 806 line_index->bytes_left_in_idat = png_ptr->idat_size + png_ptr->zstream.avail_in; 807 808 // increment the size now that we have the backing data structures. 809 // This prevents a crash in the event that png_read_row fails and 810 // we need to cleanup the partially constructed png_index_struct; 811 index->size[p] += 1; 812 813 // Skip the "step" number of rows to the next indexing row. 814 for (j = 0; j < index->step[p] && 815 i * index->step[p] + j < png_ptr->height; j++) 816 { 817 png_read_row(png_ptr, rp, NULL); 818 } 819 } 820 } 821 png_free(png_ptr, rp); 822 } 823 #endif 824 825 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 826 /* Read the entire image. If the image has an alpha channel or a tRNS 827 * chunk, and you have called png_handle_alpha()[*], you will need to 828 * initialize the image to the current image that PNG will be overlaying. 829 * We set the num_rows again here, in case it was incorrectly set in 830 * png_read_start_row() by a call to png_read_update_info() or 831 * png_start_read_image() if png_set_interlace_handling() wasn't called 832 * prior to either of these functions like it should have been. You can 833 * only call this function once. If you desire to have an image for 834 * each pass of a interlaced image, use png_read_rows() instead. 835 * 836 * [*] png_handle_alpha() does not exist yet, as of this version of libpng 837 */ 838 void PNGAPI 839 png_read_image(png_structrp png_ptr, png_bytepp image) 840 { 841 png_uint_32 i, image_height; 842 int pass, j; 843 png_bytepp rp; 844 845 png_debug(1, "in png_read_image"); 846 847 if (png_ptr == NULL) 848 return; 849 850 #ifdef PNG_READ_INTERLACING_SUPPORTED 851 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT)) 852 { 853 pass = png_set_interlace_handling(png_ptr); 854 /* And make sure transforms are initialized. */ 855 png_start_read_image(png_ptr); 856 } 857 else 858 { 859 if (png_ptr->interlaced && !(png_ptr->transformations & PNG_INTERLACE)) 860 { 861 /* Caller called png_start_read_image or png_read_update_info without 862 * first turning on the PNG_INTERLACE transform. We can fix this here, 863 * but the caller should do it! 864 */ 865 png_warning(png_ptr, "Interlace handling should be turned on when " 866 "using png_read_image"); 867 /* Make sure this is set correctly */ 868 png_ptr->num_rows = png_ptr->height; 869 } 870 871 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in 872 * the above error case. 873 */ 874 pass = png_set_interlace_handling(png_ptr); 875 } 876 #else 877 if (png_ptr->interlaced) 878 png_error(png_ptr, 879 "Cannot read interlaced image -- interlace handler disabled"); 880 881 pass = 1; 882 #endif 883 884 image_height=png_ptr->height; 885 886 for (j = 0; j < pass; j++) 887 { 888 rp = image; 889 for (i = 0; i < image_height; i++) 890 { 891 png_read_row(png_ptr, *rp, NULL); 892 rp++; 893 } 894 } 895 } 896 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 897 898 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 899 /* Read the end of the PNG file. Will not read past the end of the 900 * file, will verify the end is accurate, and will read any comments 901 * or time information at the end of the file, if info is not NULL. 902 */ 903 void PNGAPI 904 png_read_end(png_structrp png_ptr, png_inforp info_ptr) 905 { 906 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 907 int keep; 908 #endif 909 910 png_debug(1, "in png_read_end"); 911 912 if (png_ptr == NULL) 913 return; 914 915 /* If png_read_end is called in the middle of reading the rows there may 916 * still be pending IDAT data and an owned zstream. Deal with this here. 917 */ 918 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 919 if (!png_chunk_unknown_handling(png_ptr, png_IDAT)) 920 #endif 921 png_read_finish_IDAT(png_ptr); 922 923 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED 924 /* Report invalid palette index; added at libng-1.5.10 */ 925 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE && 926 png_ptr->num_palette_max > png_ptr->num_palette) 927 png_benign_error(png_ptr, "Read palette index exceeding num_palette"); 928 #endif 929 930 do 931 { 932 png_uint_32 length = png_read_chunk_header(png_ptr); 933 png_uint_32 chunk_name = png_ptr->chunk_name; 934 935 if (chunk_name == png_IEND) 936 png_handle_IEND(png_ptr, info_ptr, length); 937 938 else if (chunk_name == png_IHDR) 939 png_handle_IHDR(png_ptr, info_ptr, length); 940 941 else if (info_ptr == NULL) 942 png_crc_finish(png_ptr, length); 943 944 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 945 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0) 946 { 947 if (chunk_name == png_IDAT) 948 { 949 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT)) 950 png_benign_error(png_ptr, "Too many IDATs found"); 951 } 952 png_handle_unknown(png_ptr, info_ptr, length, keep); 953 if (chunk_name == png_PLTE) 954 png_ptr->mode |= PNG_HAVE_PLTE; 955 } 956 #endif 957 958 else if (chunk_name == png_IDAT) 959 { 960 /* Zero length IDATs are legal after the last IDAT has been 961 * read, but not after other chunks have been read. 962 */ 963 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT)) 964 png_benign_error(png_ptr, "Too many IDATs found"); 965 966 png_crc_finish(png_ptr, length); 967 } 968 else if (chunk_name == png_PLTE) 969 png_handle_PLTE(png_ptr, info_ptr, length); 970 971 #ifdef PNG_READ_bKGD_SUPPORTED 972 else if (chunk_name == png_bKGD) 973 png_handle_bKGD(png_ptr, info_ptr, length); 974 #endif 975 976 #ifdef PNG_READ_cHRM_SUPPORTED 977 else if (chunk_name == png_cHRM) 978 png_handle_cHRM(png_ptr, info_ptr, length); 979 #endif 980 981 #ifdef PNG_READ_gAMA_SUPPORTED 982 else if (chunk_name == png_gAMA) 983 png_handle_gAMA(png_ptr, info_ptr, length); 984 #endif 985 986 #ifdef PNG_READ_hIST_SUPPORTED 987 else if (chunk_name == png_hIST) 988 png_handle_hIST(png_ptr, info_ptr, length); 989 #endif 990 991 #ifdef PNG_READ_oFFs_SUPPORTED 992 else if (chunk_name == png_oFFs) 993 png_handle_oFFs(png_ptr, info_ptr, length); 994 #endif 995 996 #ifdef PNG_READ_pCAL_SUPPORTED 997 else if (chunk_name == png_pCAL) 998 png_handle_pCAL(png_ptr, info_ptr, length); 999 #endif 1000 1001 #ifdef PNG_READ_sCAL_SUPPORTED 1002 else if (chunk_name == png_sCAL) 1003 png_handle_sCAL(png_ptr, info_ptr, length); 1004 #endif 1005 1006 #ifdef PNG_READ_pHYs_SUPPORTED 1007 else if (chunk_name == png_pHYs) 1008 png_handle_pHYs(png_ptr, info_ptr, length); 1009 #endif 1010 1011 #ifdef PNG_READ_sBIT_SUPPORTED 1012 else if (chunk_name == png_sBIT) 1013 png_handle_sBIT(png_ptr, info_ptr, length); 1014 #endif 1015 1016 #ifdef PNG_READ_sRGB_SUPPORTED 1017 else if (chunk_name == png_sRGB) 1018 png_handle_sRGB(png_ptr, info_ptr, length); 1019 #endif 1020 1021 #ifdef PNG_READ_iCCP_SUPPORTED 1022 else if (chunk_name == png_iCCP) 1023 png_handle_iCCP(png_ptr, info_ptr, length); 1024 #endif 1025 1026 #ifdef PNG_READ_sPLT_SUPPORTED 1027 else if (chunk_name == png_sPLT) 1028 png_handle_sPLT(png_ptr, info_ptr, length); 1029 #endif 1030 1031 #ifdef PNG_READ_tEXt_SUPPORTED 1032 else if (chunk_name == png_tEXt) 1033 png_handle_tEXt(png_ptr, info_ptr, length); 1034 #endif 1035 1036 #ifdef PNG_READ_tIME_SUPPORTED 1037 else if (chunk_name == png_tIME) 1038 png_handle_tIME(png_ptr, info_ptr, length); 1039 #endif 1040 1041 #ifdef PNG_READ_tRNS_SUPPORTED 1042 else if (chunk_name == png_tRNS) 1043 png_handle_tRNS(png_ptr, info_ptr, length); 1044 #endif 1045 1046 #ifdef PNG_READ_zTXt_SUPPORTED 1047 else if (chunk_name == png_zTXt) 1048 png_handle_zTXt(png_ptr, info_ptr, length); 1049 #endif 1050 1051 #ifdef PNG_READ_iTXt_SUPPORTED 1052 else if (chunk_name == png_iTXt) 1053 png_handle_iTXt(png_ptr, info_ptr, length); 1054 #endif 1055 1056 else 1057 png_handle_unknown(png_ptr, info_ptr, length, 1058 PNG_HANDLE_CHUNK_AS_DEFAULT); 1059 } while (!(png_ptr->mode & PNG_HAVE_IEND)); 1060 } 1061 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 1062 1063 /* Free all memory used in the read struct */ 1064 static void 1065 png_read_destroy(png_structrp png_ptr) 1066 { 1067 png_debug(1, "in png_read_destroy"); 1068 1069 #ifdef PNG_READ_GAMMA_SUPPORTED 1070 png_destroy_gamma_table(png_ptr); 1071 #endif 1072 1073 png_free(png_ptr, png_ptr->big_row_buf); 1074 png_free(png_ptr, png_ptr->big_prev_row); 1075 png_free(png_ptr, png_ptr->read_buffer); 1076 1077 #ifdef PNG_READ_QUANTIZE_SUPPORTED 1078 png_free(png_ptr, png_ptr->palette_lookup); 1079 png_free(png_ptr, png_ptr->quantize_index); 1080 #endif 1081 1082 if (png_ptr->free_me & PNG_FREE_PLTE) 1083 png_zfree(png_ptr, png_ptr->palette); 1084 png_ptr->free_me &= ~PNG_FREE_PLTE; 1085 1086 #if defined(PNG_tRNS_SUPPORTED) || \ 1087 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) 1088 if (png_ptr->free_me & PNG_FREE_TRNS) 1089 png_free(png_ptr, png_ptr->trans_alpha); 1090 png_ptr->free_me &= ~PNG_FREE_TRNS; 1091 #endif 1092 1093 inflateEnd(&png_ptr->zstream); 1094 1095 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED 1096 png_free(png_ptr, png_ptr->save_buffer); 1097 #endif 1098 1099 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) &&\ 1100 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) 1101 png_free(png_ptr, png_ptr->unknown_chunk.data); 1102 #endif 1103 1104 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED 1105 png_free(png_ptr, png_ptr->chunk_list); 1106 #endif 1107 1108 #ifdef PNG_INDEX_SUPPORTED 1109 if (png_ptr->index) { 1110 unsigned int i, p; 1111 png_indexp index = png_ptr->index; 1112 for (p = 0; p < 7; p++) { 1113 for (i = 0; i < index->size[p]; i++) { 1114 inflateEnd(index->pass_line_index[p][i]->z_state); 1115 png_free(png_ptr, index->pass_line_index[p][i]->z_state); 1116 png_free(png_ptr, index->pass_line_index[p][i]->prev_row); 1117 png_free(png_ptr, index->pass_line_index[p][i]); 1118 } 1119 if (index->size[p] != 0) { 1120 png_free(png_ptr, index->pass_line_index[p]); 1121 } 1122 } 1123 png_free(png_ptr, index); 1124 } 1125 #endif 1126 1127 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error 1128 * callbacks are still set at this point. They are required to complete the 1129 * destruction of the png_struct itself. 1130 */ 1131 } 1132 1133 /* Free all memory used by the read */ 1134 void PNGAPI 1135 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr, 1136 png_infopp end_info_ptr_ptr) 1137 { 1138 png_structrp png_ptr = NULL; 1139 1140 png_debug(1, "in png_destroy_read_struct"); 1141 1142 if (png_ptr_ptr != NULL) 1143 png_ptr = *png_ptr_ptr; 1144 1145 if (png_ptr == NULL) 1146 return; 1147 1148 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent 1149 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API. 1150 * The extra was, apparently, unnecessary yet this hides memory leak bugs. 1151 */ 1152 png_destroy_info_struct(png_ptr, end_info_ptr_ptr); 1153 png_destroy_info_struct(png_ptr, info_ptr_ptr); 1154 1155 *png_ptr_ptr = NULL; 1156 png_read_destroy(png_ptr); 1157 png_destroy_png_struct(png_ptr); 1158 } 1159 1160 void PNGAPI 1161 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn) 1162 { 1163 if (png_ptr == NULL) 1164 return; 1165 1166 png_ptr->read_row_fn = read_row_fn; 1167 } 1168 1169 1170 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED 1171 #ifdef PNG_INFO_IMAGE_SUPPORTED 1172 void PNGAPI 1173 png_read_png(png_structrp png_ptr, png_inforp info_ptr, 1174 int transforms, 1175 voidp params) 1176 { 1177 if (png_ptr == NULL || info_ptr == NULL) 1178 return; 1179 1180 /* png_read_info() gives us all of the information from the 1181 * PNG file before the first IDAT (image data chunk). 1182 */ 1183 png_read_info(png_ptr, info_ptr); 1184 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep))) 1185 png_error(png_ptr, "Image is too high to process with png_read_png()"); 1186 1187 /* -------------- image transformations start here ------------------- */ 1188 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM 1189 * is not implemented. This will only happen in de-configured (non-default) 1190 * libpng builds. The results can be unexpected - png_read_png may return 1191 * short or mal-formed rows because the transform is skipped. 1192 */ 1193 1194 /* Tell libpng to strip 16-bit/color files down to 8 bits per color. 1195 */ 1196 if (transforms & PNG_TRANSFORM_SCALE_16) 1197 /* Added at libpng-1.5.4. "strip_16" produces the same result that it 1198 * did in earlier versions, while "scale_16" is now more accurate. 1199 */ 1200 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED 1201 png_set_scale_16(png_ptr); 1202 #else 1203 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported"); 1204 #endif 1205 1206 /* If both SCALE and STRIP are required pngrtran will effectively cancel the 1207 * latter by doing SCALE first. This is ok and allows apps not to check for 1208 * which is supported to get the right answer. 1209 */ 1210 if (transforms & PNG_TRANSFORM_STRIP_16) 1211 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED 1212 png_set_strip_16(png_ptr); 1213 #else 1214 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported"); 1215 #endif 1216 1217 /* Strip alpha bytes from the input data without combining with 1218 * the background (not recommended). 1219 */ 1220 if (transforms & PNG_TRANSFORM_STRIP_ALPHA) 1221 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED 1222 png_set_strip_alpha(png_ptr); 1223 #else 1224 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported"); 1225 #endif 1226 1227 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single 1228 * byte into separate bytes (useful for paletted and grayscale images). 1229 */ 1230 if (transforms & PNG_TRANSFORM_PACKING) 1231 #ifdef PNG_READ_PACK_SUPPORTED 1232 png_set_packing(png_ptr); 1233 #else 1234 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported"); 1235 #endif 1236 1237 /* Change the order of packed pixels to least significant bit first 1238 * (not useful if you are using png_set_packing). 1239 */ 1240 if (transforms & PNG_TRANSFORM_PACKSWAP) 1241 #ifdef PNG_READ_PACKSWAP_SUPPORTED 1242 png_set_packswap(png_ptr); 1243 #else 1244 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported"); 1245 #endif 1246 1247 /* Expand paletted colors into true RGB triplets 1248 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel 1249 * Expand paletted or RGB images with transparency to full alpha 1250 * channels so the data will be available as RGBA quartets. 1251 */ 1252 if (transforms & PNG_TRANSFORM_EXPAND) 1253 #ifdef PNG_READ_EXPAND_SUPPORTED 1254 png_set_expand(png_ptr); 1255 #else 1256 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported"); 1257 #endif 1258 1259 /* We don't handle background color or gamma transformation or quantizing. 1260 */ 1261 1262 /* Invert monochrome files to have 0 as white and 1 as black 1263 */ 1264 if (transforms & PNG_TRANSFORM_INVERT_MONO) 1265 #ifdef PNG_READ_INVERT_SUPPORTED 1266 png_set_invert_mono(png_ptr); 1267 #else 1268 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported"); 1269 #endif 1270 1271 /* If you want to shift the pixel values from the range [0,255] or 1272 * [0,65535] to the original [0,7] or [0,31], or whatever range the 1273 * colors were originally in: 1274 */ 1275 if (transforms & PNG_TRANSFORM_SHIFT) 1276 #ifdef PNG_READ_SHIFT_SUPPORTED 1277 if (info_ptr->valid & PNG_INFO_sBIT) 1278 png_set_shift(png_ptr, &info_ptr->sig_bit); 1279 #else 1280 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported"); 1281 #endif 1282 1283 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */ 1284 if (transforms & PNG_TRANSFORM_BGR) 1285 #ifdef PNG_READ_BGR_SUPPORTED 1286 png_set_bgr(png_ptr); 1287 #else 1288 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported"); 1289 #endif 1290 1291 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ 1292 if (transforms & PNG_TRANSFORM_SWAP_ALPHA) 1293 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED 1294 png_set_swap_alpha(png_ptr); 1295 #else 1296 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported"); 1297 #endif 1298 1299 /* Swap bytes of 16-bit files to least significant byte first */ 1300 if (transforms & PNG_TRANSFORM_SWAP_ENDIAN) 1301 #ifdef PNG_READ_SWAP_SUPPORTED 1302 png_set_swap(png_ptr); 1303 #else 1304 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported"); 1305 #endif 1306 1307 /* Added at libpng-1.2.41 */ 1308 /* Invert the alpha channel from opacity to transparency */ 1309 if (transforms & PNG_TRANSFORM_INVERT_ALPHA) 1310 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED 1311 png_set_invert_alpha(png_ptr); 1312 #else 1313 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported"); 1314 #endif 1315 1316 /* Added at libpng-1.2.41 */ 1317 /* Expand grayscale image to RGB */ 1318 if (transforms & PNG_TRANSFORM_GRAY_TO_RGB) 1319 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED 1320 png_set_gray_to_rgb(png_ptr); 1321 #else 1322 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported"); 1323 #endif 1324 1325 /* Added at libpng-1.5.4 */ 1326 if (transforms & PNG_TRANSFORM_EXPAND_16) 1327 #ifdef PNG_READ_EXPAND_16_SUPPORTED 1328 png_set_expand_16(png_ptr); 1329 #else 1330 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported"); 1331 #endif 1332 1333 /* We don't handle adding filler bytes */ 1334 1335 /* We use png_read_image and rely on that for interlace handling, but we also 1336 * call png_read_update_info therefore must turn on interlace handling now: 1337 */ 1338 (void)png_set_interlace_handling(png_ptr); 1339 1340 /* Optional call to gamma correct and add the background to the palette 1341 * and update info structure. REQUIRED if you are expecting libpng to 1342 * update the palette for you (i.e., you selected such a transform above). 1343 */ 1344 png_read_update_info(png_ptr, info_ptr); 1345 1346 /* -------------- image transformations end here ------------------- */ 1347 1348 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0); 1349 if (info_ptr->row_pointers == NULL) 1350 { 1351 png_uint_32 iptr; 1352 1353 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr, 1354 info_ptr->height * (sizeof (png_bytep)))); 1355 1356 for (iptr=0; iptr<info_ptr->height; iptr++) 1357 info_ptr->row_pointers[iptr] = NULL; 1358 1359 info_ptr->free_me |= PNG_FREE_ROWS; 1360 1361 for (iptr = 0; iptr < info_ptr->height; iptr++) 1362 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep, 1363 png_malloc(png_ptr, info_ptr->rowbytes)); 1364 } 1365 1366 png_read_image(png_ptr, info_ptr->row_pointers); 1367 info_ptr->valid |= PNG_INFO_IDAT; 1368 1369 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */ 1370 png_read_end(png_ptr, info_ptr); 1371 1372 PNG_UNUSED(params) 1373 } 1374 #endif /* PNG_INFO_IMAGE_SUPPORTED */ 1375 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */ 1376 1377 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED 1378 /* SIMPLIFIED READ 1379 * 1380 * This code currently relies on the sequential reader, though it could easily 1381 * be made to work with the progressive one. 1382 */ 1383 /* Arguments to png_image_finish_read: */ 1384 1385 /* Encoding of PNG data (used by the color-map code) */ 1386 # define P_NOTSET 0 /* File encoding not yet known */ 1387 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */ 1388 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */ 1389 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */ 1390 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */ 1391 1392 /* Color-map processing: after libpng has run on the PNG image further 1393 * processing may be needed to conver the data to color-map indicies. 1394 */ 1395 #define PNG_CMAP_NONE 0 1396 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */ 1397 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */ 1398 #define PNG_CMAP_RGB 3 /* Process RGB data */ 1399 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */ 1400 1401 /* The following document where the background is for each processing case. */ 1402 #define PNG_CMAP_NONE_BACKGROUND 256 1403 #define PNG_CMAP_GA_BACKGROUND 231 1404 #define PNG_CMAP_TRANS_BACKGROUND 254 1405 #define PNG_CMAP_RGB_BACKGROUND 256 1406 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216 1407 1408 typedef struct 1409 { 1410 /* Arguments: */ 1411 png_imagep image; 1412 png_voidp buffer; 1413 png_int_32 row_stride; 1414 png_voidp colormap; 1415 png_const_colorp background; 1416 /* Local variables: */ 1417 png_voidp local_row; 1418 png_voidp first_row; 1419 ptrdiff_t row_bytes; /* step between rows */ 1420 int file_encoding; /* E_ values above */ 1421 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */ 1422 int colormap_processing; /* PNG_CMAP_ values above */ 1423 } png_image_read_control; 1424 1425 /* Do all the *safe* initialization - 'safe' means that png_error won't be 1426 * called, so setting up the jmp_buf is not required. This means that anything 1427 * called from here must *not* call png_malloc - it has to call png_malloc_warn 1428 * instead so that control is returned safely back to this routine. 1429 */ 1430 static int 1431 png_image_read_init(png_imagep image) 1432 { 1433 if (image->opaque == NULL) 1434 { 1435 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image, 1436 png_safe_error, png_safe_warning); 1437 1438 /* And set the rest of the structure to NULL to ensure that the various 1439 * fields are consistent. 1440 */ 1441 memset(image, 0, (sizeof *image)); 1442 image->version = PNG_IMAGE_VERSION; 1443 1444 if (png_ptr != NULL) 1445 { 1446 png_infop info_ptr = png_create_info_struct(png_ptr); 1447 1448 if (info_ptr != NULL) 1449 { 1450 png_controlp control = png_voidcast(png_controlp, 1451 png_malloc_warn(png_ptr, (sizeof *control))); 1452 1453 if (control != NULL) 1454 { 1455 memset(control, 0, (sizeof *control)); 1456 1457 control->png_ptr = png_ptr; 1458 control->info_ptr = info_ptr; 1459 control->for_write = 0; 1460 1461 image->opaque = control; 1462 return 1; 1463 } 1464 1465 /* Error clean up */ 1466 png_destroy_info_struct(png_ptr, &info_ptr); 1467 } 1468 1469 png_destroy_read_struct(&png_ptr, NULL, NULL); 1470 } 1471 1472 return png_image_error(image, "png_image_read: out of memory"); 1473 } 1474 1475 return png_image_error(image, "png_image_read: opaque pointer not NULL"); 1476 } 1477 1478 /* Utility to find the base format of a PNG file from a png_struct. */ 1479 static png_uint_32 1480 png_image_format(png_structrp png_ptr) 1481 { 1482 png_uint_32 format = 0; 1483 1484 if (png_ptr->color_type & PNG_COLOR_MASK_COLOR) 1485 format |= PNG_FORMAT_FLAG_COLOR; 1486 1487 if (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) 1488 format |= PNG_FORMAT_FLAG_ALPHA; 1489 1490 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS 1491 * sets the png_struct fields; that's all we are interested in here. The 1492 * precise interaction with an app call to png_set_tRNS and PNG file reading 1493 * is unclear. 1494 */ 1495 else if (png_ptr->num_trans > 0) 1496 format |= PNG_FORMAT_FLAG_ALPHA; 1497 1498 if (png_ptr->bit_depth == 16) 1499 format |= PNG_FORMAT_FLAG_LINEAR; 1500 1501 if (png_ptr->color_type & PNG_COLOR_MASK_PALETTE) 1502 format |= PNG_FORMAT_FLAG_COLORMAP; 1503 1504 return format; 1505 } 1506 1507 /* Is the given gamma significantly different from sRGB? The test is the same 1508 * one used in pngrtran.c when deciding whether to do gamma correction. The 1509 * arithmetic optimizes the division by using the fact that the inverse of the 1510 * file sRGB gamma is 2.2 1511 */ 1512 static int 1513 png_gamma_not_sRGB(png_fixed_point g) 1514 { 1515 if (g < PNG_FP_1) 1516 { 1517 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */ 1518 if (g == 0) 1519 return 0; 1520 1521 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */); 1522 } 1523 1524 return 1; 1525 } 1526 1527 /* Do the main body of a 'png_image_begin_read' function; read the PNG file 1528 * header and fill in all the information. This is executed in a safe context, 1529 * unlike the init routine above. 1530 */ 1531 static int 1532 png_image_read_header(png_voidp argument) 1533 { 1534 png_imagep image = png_voidcast(png_imagep, argument); 1535 png_structrp png_ptr = image->opaque->png_ptr; 1536 png_inforp info_ptr = image->opaque->info_ptr; 1537 1538 png_set_benign_errors(png_ptr, 1/*warn*/); 1539 png_read_info(png_ptr, info_ptr); 1540 1541 /* Do this the fast way; just read directly out of png_struct. */ 1542 image->width = png_ptr->width; 1543 image->height = png_ptr->height; 1544 1545 { 1546 png_uint_32 format = png_image_format(png_ptr); 1547 1548 image->format = format; 1549 1550 #ifdef PNG_COLORSPACE_SUPPORTED 1551 /* Does the colorspace match sRGB? If there is no color endpoint 1552 * (colorant) information assume yes, otherwise require the 1553 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the 1554 * colorspace has been determined to be invalid ignore it. 1555 */ 1556 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags 1557 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB| 1558 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS)) 1559 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB; 1560 #endif 1561 } 1562 1563 /* We need the maximum number of entries regardless of the format the 1564 * application sets here. 1565 */ 1566 { 1567 png_uint_32 cmap_entries; 1568 1569 switch (png_ptr->color_type) 1570 { 1571 case PNG_COLOR_TYPE_GRAY: 1572 cmap_entries = 1U << png_ptr->bit_depth; 1573 break; 1574 1575 case PNG_COLOR_TYPE_PALETTE: 1576 cmap_entries = png_ptr->num_palette; 1577 break; 1578 1579 default: 1580 cmap_entries = 256; 1581 break; 1582 } 1583 1584 if (cmap_entries > 256) 1585 cmap_entries = 256; 1586 1587 image->colormap_entries = cmap_entries; 1588 } 1589 1590 return 1; 1591 } 1592 1593 #ifdef PNG_STDIO_SUPPORTED 1594 int PNGAPI 1595 png_image_begin_read_from_stdio(png_imagep image, FILE* file) 1596 { 1597 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1598 { 1599 if (file != NULL) 1600 { 1601 if (png_image_read_init(image)) 1602 { 1603 /* This is slightly evil, but png_init_io doesn't do anything other 1604 * than this and we haven't changed the standard IO functions so 1605 * this saves a 'safe' function. 1606 */ 1607 image->opaque->png_ptr->io_ptr = file; 1608 return png_safe_execute(image, png_image_read_header, image); 1609 } 1610 } 1611 1612 else 1613 return png_image_error(image, 1614 "png_image_begin_read_from_stdio: invalid argument"); 1615 } 1616 1617 else if (image != NULL) 1618 return png_image_error(image, 1619 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION"); 1620 1621 return 0; 1622 } 1623 1624 int PNGAPI 1625 png_image_begin_read_from_file(png_imagep image, const char *file_name) 1626 { 1627 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1628 { 1629 if (file_name != NULL) 1630 { 1631 FILE *fp = fopen(file_name, "rb"); 1632 1633 if (fp != NULL) 1634 { 1635 if (png_image_read_init(image)) 1636 { 1637 image->opaque->png_ptr->io_ptr = fp; 1638 image->opaque->owned_file = 1; 1639 return png_safe_execute(image, png_image_read_header, image); 1640 } 1641 1642 /* Clean up: just the opened file. */ 1643 (void)fclose(fp); 1644 } 1645 1646 else 1647 return png_image_error(image, strerror(errno)); 1648 } 1649 1650 else 1651 return png_image_error(image, 1652 "png_image_begin_read_from_file: invalid argument"); 1653 } 1654 1655 else if (image != NULL) 1656 return png_image_error(image, 1657 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION"); 1658 1659 return 0; 1660 } 1661 #endif /* PNG_STDIO_SUPPORTED */ 1662 1663 static void PNGCBAPI 1664 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need) 1665 { 1666 if (png_ptr != NULL) 1667 { 1668 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr); 1669 if (image != NULL) 1670 { 1671 png_controlp cp = image->opaque; 1672 if (cp != NULL) 1673 { 1674 png_const_bytep memory = cp->memory; 1675 png_size_t size = cp->size; 1676 1677 if (memory != NULL && size >= need) 1678 { 1679 memcpy(out, memory, need); 1680 cp->memory = memory + need; 1681 cp->size = size - need; 1682 return; 1683 } 1684 1685 png_error(png_ptr, "read beyond end of data"); 1686 } 1687 } 1688 1689 png_error(png_ptr, "invalid memory read"); 1690 } 1691 } 1692 1693 int PNGAPI png_image_begin_read_from_memory(png_imagep image, 1694 png_const_voidp memory, png_size_t size) 1695 { 1696 if (image != NULL && image->version == PNG_IMAGE_VERSION) 1697 { 1698 if (memory != NULL && size > 0) 1699 { 1700 if (png_image_read_init(image)) 1701 { 1702 /* Now set the IO functions to read from the memory buffer and 1703 * store it into io_ptr. Again do this in-place to avoid calling a 1704 * libpng function that requires error handling. 1705 */ 1706 image->opaque->memory = png_voidcast(png_const_bytep, memory); 1707 image->opaque->size = size; 1708 image->opaque->png_ptr->io_ptr = image; 1709 image->opaque->png_ptr->read_data_fn = png_image_memory_read; 1710 1711 return png_safe_execute(image, png_image_read_header, image); 1712 } 1713 } 1714 1715 else 1716 return png_image_error(image, 1717 "png_image_begin_read_from_memory: invalid argument"); 1718 } 1719 1720 else if (image != NULL) 1721 return png_image_error(image, 1722 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION"); 1723 1724 return 0; 1725 } 1726 1727 /* Utility function to skip chunks that are not used by the simplified image 1728 * read functions and an appropriate macro to call it. 1729 */ 1730 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED 1731 static void 1732 png_image_skip_unused_chunks(png_structrp png_ptr) 1733 { 1734 /* Prepare the reader to ignore all recognized chunks whose data will not 1735 * be used, i.e., all chunks recognized by libpng except for those 1736 * involved in basic image reading: 1737 * 1738 * IHDR, PLTE, IDAT, IEND 1739 * 1740 * Or image data handling: 1741 * 1742 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT. 1743 * 1744 * This provides a small performance improvement and eliminates any 1745 * potential vulnerability to security problems in the unused chunks. 1746 * 1747 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored 1748 * too. This allows the simplified API to be compiled without iCCP support, 1749 * however if the support is there the chunk is still checked to detect 1750 * errors (which are unfortunately quite common.) 1751 */ 1752 { 1753 static PNG_CONST png_byte chunks_to_process[] = { 1754 98, 75, 71, 68, '\0', /* bKGD */ 1755 99, 72, 82, 77, '\0', /* cHRM */ 1756 103, 65, 77, 65, '\0', /* gAMA */ 1757 # ifdef PNG_READ_iCCP_SUPPORTED 1758 105, 67, 67, 80, '\0', /* iCCP */ 1759 # endif 1760 115, 66, 73, 84, '\0', /* sBIT */ 1761 115, 82, 71, 66, '\0', /* sRGB */ 1762 }; 1763 1764 /* Ignore unknown chunks and all other chunks except for the 1765 * IHDR, PLTE, tRNS, IDAT, and IEND chunks. 1766 */ 1767 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER, 1768 NULL, -1); 1769 1770 /* But do not ignore image data handling chunks */ 1771 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT, 1772 chunks_to_process, (sizeof chunks_to_process)/5); 1773 } 1774 } 1775 1776 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p) 1777 #else 1778 # define PNG_SKIP_CHUNKS(p) ((void)0) 1779 #endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */ 1780 1781 /* The following macro gives the exact rounded answer for all values in the 1782 * range 0..255 (it actually divides by 51.2, but the rounding still generates 1783 * the correct numbers 0..5 1784 */ 1785 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8) 1786 1787 /* Utility functions to make particular color-maps */ 1788 static void 1789 set_file_encoding(png_image_read_control *display) 1790 { 1791 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma; 1792 if (png_gamma_significant(g)) 1793 { 1794 if (png_gamma_not_sRGB(g)) 1795 { 1796 display->file_encoding = P_FILE; 1797 display->gamma_to_linear = png_reciprocal(g); 1798 } 1799 1800 else 1801 display->file_encoding = P_sRGB; 1802 } 1803 1804 else 1805 display->file_encoding = P_LINEAR8; 1806 } 1807 1808 static unsigned int 1809 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding) 1810 { 1811 if (encoding == P_FILE) /* double check */ 1812 encoding = display->file_encoding; 1813 1814 if (encoding == P_NOTSET) /* must be the file encoding */ 1815 { 1816 set_file_encoding(display); 1817 encoding = display->file_encoding; 1818 } 1819 1820 switch (encoding) 1821 { 1822 case P_FILE: 1823 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear); 1824 break; 1825 1826 case P_sRGB: 1827 value = png_sRGB_table[value]; 1828 break; 1829 1830 case P_LINEAR: 1831 break; 1832 1833 case P_LINEAR8: 1834 value *= 257; 1835 break; 1836 1837 default: 1838 png_error(display->image->opaque->png_ptr, 1839 "unexpected encoding (internal error)"); 1840 break; 1841 } 1842 1843 return value; 1844 } 1845 1846 static png_uint_32 1847 png_colormap_compose(png_image_read_control *display, 1848 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha, 1849 png_uint_32 background, int encoding) 1850 { 1851 /* The file value is composed on the background, the background has the given 1852 * encoding and so does the result, the file is encoded with P_FILE and the 1853 * file and alpha are 8-bit values. The (output) encoding will always be 1854 * P_LINEAR or P_sRGB. 1855 */ 1856 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding); 1857 png_uint_32 b = decode_gamma(display, background, encoding); 1858 1859 /* The alpha is always an 8-bit value (it comes from the palette), the value 1860 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires. 1861 */ 1862 f = f * alpha + b * (255-alpha); 1863 1864 if (encoding == P_LINEAR) 1865 { 1866 /* Scale to 65535; divide by 255, approximately (in fact this is extremely 1867 * accurate, it divides by 255.00000005937181414556, with no overflow.) 1868 */ 1869 f *= 257; /* Now scaled by 65535 */ 1870 f += f >> 16; 1871 f = (f+32768) >> 16; 1872 } 1873 1874 else /* P_sRGB */ 1875 f = PNG_sRGB_FROM_LINEAR(f); 1876 1877 return f; 1878 } 1879 1880 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must 1881 * be 8-bit. 1882 */ 1883 static void 1884 png_create_colormap_entry(png_image_read_control *display, 1885 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue, 1886 png_uint_32 alpha, int encoding) 1887 { 1888 png_imagep image = display->image; 1889 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) ? 1890 P_LINEAR : P_sRGB; 1891 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 && 1892 (red != green || green != blue); 1893 1894 if (ip > 255) 1895 png_error(image->opaque->png_ptr, "color-map index out of range"); 1896 1897 /* Update the cache with whether the file gamma is significantly different 1898 * from sRGB. 1899 */ 1900 if (encoding == P_FILE) 1901 { 1902 if (display->file_encoding == P_NOTSET) 1903 set_file_encoding(display); 1904 1905 /* Note that the cached value may be P_FILE too, but if it is then the 1906 * gamma_to_linear member has been set. 1907 */ 1908 encoding = display->file_encoding; 1909 } 1910 1911 if (encoding == P_FILE) 1912 { 1913 png_fixed_point g = display->gamma_to_linear; 1914 1915 red = png_gamma_16bit_correct(red*257, g); 1916 green = png_gamma_16bit_correct(green*257, g); 1917 blue = png_gamma_16bit_correct(blue*257, g); 1918 1919 if (convert_to_Y || output_encoding == P_LINEAR) 1920 { 1921 alpha *= 257; 1922 encoding = P_LINEAR; 1923 } 1924 1925 else 1926 { 1927 red = PNG_sRGB_FROM_LINEAR(red * 255); 1928 green = PNG_sRGB_FROM_LINEAR(green * 255); 1929 blue = PNG_sRGB_FROM_LINEAR(blue * 255); 1930 encoding = P_sRGB; 1931 } 1932 } 1933 1934 else if (encoding == P_LINEAR8) 1935 { 1936 /* This encoding occurs quite frequently in test cases because PngSuite 1937 * includes a gAMA 1.0 chunk with most images. 1938 */ 1939 red *= 257; 1940 green *= 257; 1941 blue *= 257; 1942 alpha *= 257; 1943 encoding = P_LINEAR; 1944 } 1945 1946 else if (encoding == P_sRGB && (convert_to_Y || output_encoding == P_LINEAR)) 1947 { 1948 /* The values are 8-bit sRGB values, but must be converted to 16-bit 1949 * linear. 1950 */ 1951 red = png_sRGB_table[red]; 1952 green = png_sRGB_table[green]; 1953 blue = png_sRGB_table[blue]; 1954 alpha *= 257; 1955 encoding = P_LINEAR; 1956 } 1957 1958 /* This is set if the color isn't gray but the output is. */ 1959 if (encoding == P_LINEAR) 1960 { 1961 if (convert_to_Y) 1962 { 1963 /* NOTE: these values are copied from png_do_rgb_to_gray */ 1964 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green + 1965 (png_uint_32)2366 * blue; 1966 1967 if (output_encoding == P_LINEAR) 1968 y = (y + 16384) >> 15; 1969 1970 else 1971 { 1972 /* y is scaled by 32768, we need it scaled by 255: */ 1973 y = (y + 128) >> 8; 1974 y *= 255; 1975 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7); 1976 encoding = P_sRGB; 1977 } 1978 1979 blue = red = green = y; 1980 } 1981 1982 else if (output_encoding == P_sRGB) 1983 { 1984 red = PNG_sRGB_FROM_LINEAR(red * 255); 1985 green = PNG_sRGB_FROM_LINEAR(green * 255); 1986 blue = PNG_sRGB_FROM_LINEAR(blue * 255); 1987 alpha = PNG_DIV257(alpha); 1988 encoding = P_sRGB; 1989 } 1990 } 1991 1992 if (encoding != output_encoding) 1993 png_error(image->opaque->png_ptr, "bad encoding (internal error)"); 1994 1995 /* Store the value. */ 1996 { 1997 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 1998 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 && 1999 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0; 2000 # else 2001 # define afirst 0 2002 # endif 2003 # ifdef PNG_FORMAT_BGR_SUPPORTED 2004 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) ? 2 : 0; 2005 # else 2006 # define bgr 0 2007 # endif 2008 2009 if (output_encoding == P_LINEAR) 2010 { 2011 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap); 2012 2013 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format); 2014 2015 /* The linear 16-bit values must be pre-multiplied by the alpha channel 2016 * value, if less than 65535 (this is, effectively, composite on black 2017 * if the alpha channel is removed.) 2018 */ 2019 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format)) 2020 { 2021 case 4: 2022 entry[afirst ? 0 : 3] = (png_uint_16)alpha; 2023 /* FALL THROUGH */ 2024 2025 case 3: 2026 if (alpha < 65535) 2027 { 2028 if (alpha > 0) 2029 { 2030 blue = (blue * alpha + 32767U)/65535U; 2031 green = (green * alpha + 32767U)/65535U; 2032 red = (red * alpha + 32767U)/65535U; 2033 } 2034 2035 else 2036 red = green = blue = 0; 2037 } 2038 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue; 2039 entry[afirst + 1] = (png_uint_16)green; 2040 entry[afirst + bgr] = (png_uint_16)red; 2041 break; 2042 2043 case 2: 2044 entry[1 ^ afirst] = (png_uint_16)alpha; 2045 /* FALL THROUGH */ 2046 2047 case 1: 2048 if (alpha < 65535) 2049 { 2050 if (alpha > 0) 2051 green = (green * alpha + 32767U)/65535U; 2052 2053 else 2054 green = 0; 2055 } 2056 entry[afirst] = (png_uint_16)green; 2057 break; 2058 2059 default: 2060 break; 2061 } 2062 } 2063 2064 else /* output encoding is P_sRGB */ 2065 { 2066 png_bytep entry = png_voidcast(png_bytep, display->colormap); 2067 2068 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format); 2069 2070 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format)) 2071 { 2072 case 4: 2073 entry[afirst ? 0 : 3] = (png_byte)alpha; 2074 case 3: 2075 entry[afirst + (2 ^ bgr)] = (png_byte)blue; 2076 entry[afirst + 1] = (png_byte)green; 2077 entry[afirst + bgr] = (png_byte)red; 2078 break; 2079 2080 case 2: 2081 entry[1 ^ afirst] = (png_byte)alpha; 2082 case 1: 2083 entry[afirst] = (png_byte)green; 2084 break; 2085 2086 default: 2087 break; 2088 } 2089 } 2090 2091 # ifdef afirst 2092 # undef afirst 2093 # endif 2094 # ifdef bgr 2095 # undef bgr 2096 # endif 2097 } 2098 } 2099 2100 static int 2101 make_gray_file_colormap(png_image_read_control *display) 2102 { 2103 unsigned int i; 2104 2105 for (i=0; i<256; ++i) 2106 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE); 2107 2108 return i; 2109 } 2110 2111 static int 2112 make_gray_colormap(png_image_read_control *display) 2113 { 2114 unsigned int i; 2115 2116 for (i=0; i<256; ++i) 2117 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB); 2118 2119 return i; 2120 } 2121 #define PNG_GRAY_COLORMAP_ENTRIES 256 2122 2123 static int 2124 make_ga_colormap(png_image_read_control *display) 2125 { 2126 unsigned int i, a; 2127 2128 /* Alpha is retained, the output will be a color-map with entries 2129 * selected by six levels of alpha. One transparent entry, 6 gray 2130 * levels for all the intermediate alpha values, leaving 230 entries 2131 * for the opaque grays. The color-map entries are the six values 2132 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the 2133 * relevant entry. 2134 * 2135 * if (alpha > 229) // opaque 2136 * { 2137 * // The 231 entries are selected to make the math below work: 2138 * base = 0; 2139 * entry = (231 * gray + 128) >> 8; 2140 * } 2141 * else if (alpha < 26) // transparent 2142 * { 2143 * base = 231; 2144 * entry = 0; 2145 * } 2146 * else // partially opaque 2147 * { 2148 * base = 226 + 6 * PNG_DIV51(alpha); 2149 * entry = PNG_DIV51(gray); 2150 * } 2151 */ 2152 i = 0; 2153 while (i < 231) 2154 { 2155 unsigned int gray = (i * 256 + 115) / 231; 2156 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB); 2157 } 2158 2159 /* 255 is used here for the component values for consistency with the code 2160 * that undoes premultiplication in pngwrite.c. 2161 */ 2162 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB); 2163 2164 for (a=1; a<5; ++a) 2165 { 2166 unsigned int g; 2167 2168 for (g=0; g<6; ++g) 2169 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51, 2170 P_sRGB); 2171 } 2172 2173 return i; 2174 } 2175 2176 #define PNG_GA_COLORMAP_ENTRIES 256 2177 2178 static int 2179 make_rgb_colormap(png_image_read_control *display) 2180 { 2181 unsigned int i, r; 2182 2183 /* Build a 6x6x6 opaque RGB cube */ 2184 for (i=r=0; r<6; ++r) 2185 { 2186 unsigned int g; 2187 2188 for (g=0; g<6; ++g) 2189 { 2190 unsigned int b; 2191 2192 for (b=0; b<6; ++b) 2193 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255, 2194 P_sRGB); 2195 } 2196 } 2197 2198 return i; 2199 } 2200 2201 #define PNG_RGB_COLORMAP_ENTRIES 216 2202 2203 /* Return a palette index to the above palette given three 8-bit sRGB values. */ 2204 #define PNG_RGB_INDEX(r,g,b) \ 2205 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b))) 2206 2207 static int 2208 png_image_read_colormap(png_voidp argument) 2209 { 2210 png_image_read_control *display = 2211 png_voidcast(png_image_read_control*, argument); 2212 const png_imagep image = display->image; 2213 2214 const png_structrp png_ptr = image->opaque->png_ptr; 2215 const png_uint_32 output_format = image->format; 2216 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) ? 2217 P_LINEAR : P_sRGB; 2218 2219 unsigned int cmap_entries; 2220 unsigned int output_processing; /* Output processing option */ 2221 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */ 2222 2223 /* Background information; the background color and the index of this color 2224 * in the color-map if it exists (else 256). 2225 */ 2226 unsigned int background_index = 256; 2227 png_uint_32 back_r, back_g, back_b; 2228 2229 /* Flags to accumulate things that need to be done to the input. */ 2230 int expand_tRNS = 0; 2231 2232 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is 2233 * very difficult to do, the results look awful, and it is difficult to see 2234 * what possible use it is because the application can't control the 2235 * color-map. 2236 */ 2237 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 || 2238 png_ptr->num_trans > 0) /* alpha in input */ && 2239 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */) 2240 { 2241 if (output_encoding == P_LINEAR) /* compose on black */ 2242 back_b = back_g = back_r = 0; 2243 2244 else if (display->background == NULL /* no way to remove it */) 2245 png_error(png_ptr, 2246 "a background color must be supplied to remove alpha/transparency"); 2247 2248 /* Get a copy of the background color (this avoids repeating the checks 2249 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the 2250 * output format. 2251 */ 2252 else 2253 { 2254 back_g = display->background->green; 2255 if (output_format & PNG_FORMAT_FLAG_COLOR) 2256 { 2257 back_r = display->background->red; 2258 back_b = display->background->blue; 2259 } 2260 else 2261 back_b = back_r = back_g; 2262 } 2263 } 2264 2265 else if (output_encoding == P_LINEAR) 2266 back_b = back_r = back_g = 65535; 2267 2268 else 2269 back_b = back_r = back_g = 255; 2270 2271 /* Default the input file gamma if required - this is necessary because 2272 * libpng assumes that if no gamma information is present the data is in the 2273 * output format, but the simplified API deduces the gamma from the input 2274 * format. 2275 */ 2276 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0) 2277 { 2278 /* Do this directly, not using the png_colorspace functions, to ensure 2279 * that it happens even if the colorspace is invalid (though probably if 2280 * it is the setting will be ignored) Note that the same thing can be 2281 * achieved at the application interface with png_set_gAMA. 2282 */ 2283 if (png_ptr->bit_depth == 16 && 2284 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0) 2285 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR; 2286 2287 else 2288 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE; 2289 2290 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA; 2291 } 2292 2293 /* Decide what to do based on the PNG color type of the input data. The 2294 * utility function png_create_colormap_entry deals with most aspects of the 2295 * output transformations; this code works out how to produce bytes of 2296 * color-map entries from the original format. 2297 */ 2298 switch (png_ptr->color_type) 2299 { 2300 case PNG_COLOR_TYPE_GRAY: 2301 if (png_ptr->bit_depth <= 8) 2302 { 2303 /* There at most 256 colors in the output, regardless of 2304 * transparency. 2305 */ 2306 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0; 2307 2308 cmap_entries = 1U << png_ptr->bit_depth; 2309 if (cmap_entries > image->colormap_entries) 2310 png_error(png_ptr, "gray[8] color-map: too few entries"); 2311 2312 step = 255 / (cmap_entries - 1); 2313 output_processing = PNG_CMAP_NONE; 2314 2315 /* If there is a tRNS chunk then this either selects a transparent 2316 * value or, if the output has no alpha, the background color. 2317 */ 2318 if (png_ptr->num_trans > 0) 2319 { 2320 trans = png_ptr->trans_color.gray; 2321 2322 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) 2323 back_alpha = output_encoding == P_LINEAR ? 65535 : 255; 2324 } 2325 2326 /* png_create_colormap_entry just takes an RGBA and writes the 2327 * corresponding color-map entry using the format from 'image', 2328 * including the required conversion to sRGB or linear as 2329 * appropriate. The input values are always either sRGB (if the 2330 * gamma correction flag is 0) or 0..255 scaled file encoded values 2331 * (if the function must gamma correct them). 2332 */ 2333 for (i=val=0; i<cmap_entries; ++i, val += step) 2334 { 2335 /* 'i' is a file value. While this will result in duplicated 2336 * entries for 8-bit non-sRGB encoded files it is necessary to 2337 * have non-gamma corrected values to do tRNS handling. 2338 */ 2339 if (i != trans) 2340 png_create_colormap_entry(display, i, val, val, val, 255, 2341 P_FILE/*8-bit with file gamma*/); 2342 2343 /* Else this entry is transparent. The colors don't matter if 2344 * there is an alpha channel (back_alpha == 0), but it does no 2345 * harm to pass them in; the values are not set above so this 2346 * passes in white. 2347 * 2348 * NOTE: this preserves the full precision of the application 2349 * supplied background color when it is used. 2350 */ 2351 else 2352 png_create_colormap_entry(display, i, back_r, back_g, back_b, 2353 back_alpha, output_encoding); 2354 } 2355 2356 /* We need libpng to preserve the original encoding. */ 2357 data_encoding = P_FILE; 2358 2359 /* The rows from libpng, while technically gray values, are now also 2360 * color-map indicies; however, they may need to be expanded to 1 2361 * byte per pixel. This is what png_set_packing does (i.e., it 2362 * unpacks the bit values into bytes.) 2363 */ 2364 if (png_ptr->bit_depth < 8) 2365 png_set_packing(png_ptr); 2366 } 2367 2368 else /* bit depth is 16 */ 2369 { 2370 /* The 16-bit input values can be converted directly to 8-bit gamma 2371 * encoded values; however, if a tRNS chunk is present 257 color-map 2372 * entries are required. This means that the extra entry requires 2373 * special processing; add an alpha channel, sacrifice gray level 2374 * 254 and convert transparent (alpha==0) entries to that. 2375 * 2376 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the 2377 * same time to minimize quality loss. If a tRNS chunk is present 2378 * this means libpng must handle it too; otherwise it is impossible 2379 * to do the exact match on the 16-bit value. 2380 * 2381 * If the output has no alpha channel *and* the background color is 2382 * gray then it is possible to let libpng handle the substitution by 2383 * ensuring that the corresponding gray level matches the background 2384 * color exactly. 2385 */ 2386 data_encoding = P_sRGB; 2387 2388 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2389 png_error(png_ptr, "gray[16] color-map: too few entries"); 2390 2391 cmap_entries = make_gray_colormap(display); 2392 2393 if (png_ptr->num_trans > 0) 2394 { 2395 unsigned int back_alpha; 2396 2397 if (output_format & PNG_FORMAT_FLAG_ALPHA) 2398 back_alpha = 0; 2399 2400 else 2401 { 2402 if (back_r == back_g && back_g == back_b) 2403 { 2404 /* Background is gray; no special processing will be 2405 * required. 2406 */ 2407 png_color_16 c; 2408 png_uint_32 gray = back_g; 2409 2410 if (output_encoding == P_LINEAR) 2411 { 2412 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2413 2414 /* And make sure the corresponding palette entry 2415 * matches. 2416 */ 2417 png_create_colormap_entry(display, gray, back_g, back_g, 2418 back_g, 65535, P_LINEAR); 2419 } 2420 2421 /* The background passed to libpng, however, must be the 2422 * sRGB value. 2423 */ 2424 c.index = 0; /*unused*/ 2425 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2426 2427 /* NOTE: does this work without expanding tRNS to alpha? 2428 * It should be the color->gray case below apparently 2429 * doesn't. 2430 */ 2431 png_set_background_fixed(png_ptr, &c, 2432 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2433 0/*gamma: not used*/); 2434 2435 output_processing = PNG_CMAP_NONE; 2436 break; 2437 } 2438 2439 back_alpha = output_encoding == P_LINEAR ? 65535 : 255; 2440 } 2441 2442 /* output_processing means that the libpng-processed row will be 2443 * 8-bit GA and it has to be processing to single byte color-map 2444 * values. Entry 254 is replaced by either a completely 2445 * transparent entry or by the background color at full 2446 * precision (and the background color is not a simple gray leve 2447 * in this case.) 2448 */ 2449 expand_tRNS = 1; 2450 output_processing = PNG_CMAP_TRANS; 2451 background_index = 254; 2452 2453 /* And set (overwrite) color-map entry 254 to the actual 2454 * background color at full precision. 2455 */ 2456 png_create_colormap_entry(display, 254, back_r, back_g, back_b, 2457 back_alpha, output_encoding); 2458 } 2459 2460 else 2461 output_processing = PNG_CMAP_NONE; 2462 } 2463 break; 2464 2465 case PNG_COLOR_TYPE_GRAY_ALPHA: 2466 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum 2467 * of 65536 combinations. If, however, the alpha channel is to be 2468 * removed there are only 256 possibilities if the background is gray. 2469 * (Otherwise there is a subset of the 65536 possibilities defined by 2470 * the triangle between black, white and the background color.) 2471 * 2472 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to 2473 * worry about tRNS matching - tRNS is ignored if there is an alpha 2474 * channel. 2475 */ 2476 data_encoding = P_sRGB; 2477 2478 if (output_format & PNG_FORMAT_FLAG_ALPHA) 2479 { 2480 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2481 png_error(png_ptr, "gray+alpha color-map: too few entries"); 2482 2483 cmap_entries = make_ga_colormap(display); 2484 2485 background_index = PNG_CMAP_GA_BACKGROUND; 2486 output_processing = PNG_CMAP_GA; 2487 } 2488 2489 else /* alpha is removed */ 2490 { 2491 /* Alpha must be removed as the PNG data is processed when the 2492 * background is a color because the G and A channels are 2493 * independent and the vector addition (non-parallel vectors) is a 2494 * 2-D problem. 2495 * 2496 * This can be reduced to the same algorithm as above by making a 2497 * colormap containing gray levels (for the opaque grays), a 2498 * background entry (for a transparent pixel) and a set of four six 2499 * level color values, one set for each intermediate alpha value. 2500 * See the comments in make_ga_colormap for how this works in the 2501 * per-pixel processing. 2502 * 2503 * If the background is gray, however, we only need a 256 entry gray 2504 * level color map. It is sufficient to make the entry generated 2505 * for the background color be exactly the color specified. 2506 */ 2507 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 || 2508 (back_r == back_g && back_g == back_b)) 2509 { 2510 /* Background is gray; no special processing will be required. */ 2511 png_color_16 c; 2512 png_uint_32 gray = back_g; 2513 2514 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2515 png_error(png_ptr, "gray-alpha color-map: too few entries"); 2516 2517 cmap_entries = make_gray_colormap(display); 2518 2519 if (output_encoding == P_LINEAR) 2520 { 2521 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2522 2523 /* And make sure the corresponding palette entry matches. */ 2524 png_create_colormap_entry(display, gray, back_g, back_g, 2525 back_g, 65535, P_LINEAR); 2526 } 2527 2528 /* The background passed to libpng, however, must be the sRGB 2529 * value. 2530 */ 2531 c.index = 0; /*unused*/ 2532 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2533 2534 png_set_background_fixed(png_ptr, &c, 2535 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2536 0/*gamma: not used*/); 2537 2538 output_processing = PNG_CMAP_NONE; 2539 } 2540 2541 else 2542 { 2543 png_uint_32 i, a; 2544 2545 /* This is the same as png_make_ga_colormap, above, except that 2546 * the entries are all opaque. 2547 */ 2548 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2549 png_error(png_ptr, "ga-alpha color-map: too few entries"); 2550 2551 i = 0; 2552 while (i < 231) 2553 { 2554 png_uint_32 gray = (i * 256 + 115) / 231; 2555 png_create_colormap_entry(display, i++, gray, gray, gray, 2556 255, P_sRGB); 2557 } 2558 2559 /* NOTE: this preserves the full precision of the application 2560 * background color. 2561 */ 2562 background_index = i; 2563 png_create_colormap_entry(display, i++, back_r, back_g, back_b, 2564 output_encoding == P_LINEAR ? 65535U : 255U, output_encoding); 2565 2566 /* For non-opaque input composite on the sRGB background - this 2567 * requires inverting the encoding for each component. The input 2568 * is still converted to the sRGB encoding because this is a 2569 * reasonable approximate to the logarithmic curve of human 2570 * visual sensitivity, at least over the narrow range which PNG 2571 * represents. Consequently 'G' is always sRGB encoded, while 2572 * 'A' is linear. We need the linear background colors. 2573 */ 2574 if (output_encoding == P_sRGB) /* else already linear */ 2575 { 2576 /* This may produce a value not exactly matching the 2577 * background, but that's ok because these numbers are only 2578 * used when alpha != 0 2579 */ 2580 back_r = png_sRGB_table[back_r]; 2581 back_g = png_sRGB_table[back_g]; 2582 back_b = png_sRGB_table[back_b]; 2583 } 2584 2585 for (a=1; a<5; ++a) 2586 { 2587 unsigned int g; 2588 2589 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled 2590 * by an 8-bit alpha value (0..255). 2591 */ 2592 png_uint_32 alpha = 51 * a; 2593 png_uint_32 back_rx = (255-alpha) * back_r; 2594 png_uint_32 back_gx = (255-alpha) * back_g; 2595 png_uint_32 back_bx = (255-alpha) * back_b; 2596 2597 for (g=0; g<6; ++g) 2598 { 2599 png_uint_32 gray = png_sRGB_table[g*51] * alpha; 2600 2601 png_create_colormap_entry(display, i++, 2602 PNG_sRGB_FROM_LINEAR(gray + back_rx), 2603 PNG_sRGB_FROM_LINEAR(gray + back_gx), 2604 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB); 2605 } 2606 } 2607 2608 cmap_entries = i; 2609 output_processing = PNG_CMAP_GA; 2610 } 2611 } 2612 break; 2613 2614 case PNG_COLOR_TYPE_RGB: 2615 case PNG_COLOR_TYPE_RGB_ALPHA: 2616 /* Exclude the case where the output is gray; we can always handle this 2617 * with the cases above. 2618 */ 2619 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0) 2620 { 2621 /* The color-map will be grayscale, so we may as well convert the 2622 * input RGB values to a simple grayscale and use the grayscale 2623 * code above. 2624 * 2625 * NOTE: calling this apparently damages the recognition of the 2626 * transparent color in background color handling; call 2627 * png_set_tRNS_to_alpha before png_set_background_fixed. 2628 */ 2629 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1, 2630 -1); 2631 data_encoding = P_sRGB; 2632 2633 /* The output will now be one or two 8-bit gray or gray+alpha 2634 * channels. The more complex case arises when the input has alpha. 2635 */ 2636 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2637 png_ptr->num_trans > 0) && 2638 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0) 2639 { 2640 /* Both input and output have an alpha channel, so no background 2641 * processing is required; just map the GA bytes to the right 2642 * color-map entry. 2643 */ 2644 expand_tRNS = 1; 2645 2646 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries) 2647 png_error(png_ptr, "rgb[ga] color-map: too few entries"); 2648 2649 cmap_entries = make_ga_colormap(display); 2650 background_index = PNG_CMAP_GA_BACKGROUND; 2651 output_processing = PNG_CMAP_GA; 2652 } 2653 2654 else 2655 { 2656 /* Either the input or the output has no alpha channel, so there 2657 * will be no non-opaque pixels in the color-map; it will just be 2658 * grayscale. 2659 */ 2660 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries) 2661 png_error(png_ptr, "rgb[gray] color-map: too few entries"); 2662 2663 /* Ideally this code would use libpng to do the gamma correction, 2664 * but if an input alpha channel is to be removed we will hit the 2665 * libpng bug in gamma+compose+rgb-to-gray (the double gamma 2666 * correction bug). Fix this by dropping the gamma correction in 2667 * this case and doing it in the palette; this will result in 2668 * duplicate palette entries, but that's better than the 2669 * alternative of double gamma correction. 2670 */ 2671 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2672 png_ptr->num_trans > 0) && 2673 png_gamma_not_sRGB(png_ptr->colorspace.gamma)) 2674 { 2675 cmap_entries = make_gray_file_colormap(display); 2676 data_encoding = P_FILE; 2677 } 2678 2679 else 2680 cmap_entries = make_gray_colormap(display); 2681 2682 /* But if the input has alpha or transparency it must be removed 2683 */ 2684 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2685 png_ptr->num_trans > 0) 2686 { 2687 png_color_16 c; 2688 png_uint_32 gray = back_g; 2689 2690 /* We need to ensure that the application background exists in 2691 * the colormap and that completely transparent pixels map to 2692 * it. Achieve this simply by ensuring that the entry 2693 * selected for the background really is the background color. 2694 */ 2695 if (data_encoding == P_FILE) /* from the fixup above */ 2696 { 2697 /* The app supplied a gray which is in output_encoding, we 2698 * need to convert it to a value of the input (P_FILE) 2699 * encoding then set this palette entry to the required 2700 * output encoding. 2701 */ 2702 if (output_encoding == P_sRGB) 2703 gray = png_sRGB_table[gray]; /* now P_LINEAR */ 2704 2705 gray = PNG_DIV257(png_gamma_16bit_correct(gray, 2706 png_ptr->colorspace.gamma)); /* now P_FILE */ 2707 2708 /* And make sure the corresponding palette entry contains 2709 * exactly the required sRGB value. 2710 */ 2711 png_create_colormap_entry(display, gray, back_g, back_g, 2712 back_g, 0/*unused*/, output_encoding); 2713 } 2714 2715 else if (output_encoding == P_LINEAR) 2716 { 2717 gray = PNG_sRGB_FROM_LINEAR(gray * 255); 2718 2719 /* And make sure the corresponding palette entry matches. 2720 */ 2721 png_create_colormap_entry(display, gray, back_g, back_g, 2722 back_g, 0/*unused*/, P_LINEAR); 2723 } 2724 2725 /* The background passed to libpng, however, must be the 2726 * output (normally sRGB) value. 2727 */ 2728 c.index = 0; /*unused*/ 2729 c.gray = c.red = c.green = c.blue = (png_uint_16)gray; 2730 2731 /* NOTE: the following is apparently a bug in libpng. Without 2732 * it the transparent color recognition in 2733 * png_set_background_fixed seems to go wrong. 2734 */ 2735 expand_tRNS = 1; 2736 png_set_background_fixed(png_ptr, &c, 2737 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2738 0/*gamma: not used*/); 2739 } 2740 2741 output_processing = PNG_CMAP_NONE; 2742 } 2743 } 2744 2745 else /* output is color */ 2746 { 2747 /* We could use png_quantize here so long as there is no transparent 2748 * color or alpha; png_quantize ignores alpha. Easier overall just 2749 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube. 2750 * Consequently we always want libpng to produce sRGB data. 2751 */ 2752 data_encoding = P_sRGB; 2753 2754 /* Is there any transparency or alpha? */ 2755 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA || 2756 png_ptr->num_trans > 0) 2757 { 2758 /* Is there alpha in the output too? If so all four channels are 2759 * processed into a special RGB cube with alpha support. 2760 */ 2761 if (output_format & PNG_FORMAT_FLAG_ALPHA) 2762 { 2763 png_uint_32 r; 2764 2765 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries) 2766 png_error(png_ptr, "rgb+alpha color-map: too few entries"); 2767 2768 cmap_entries = make_rgb_colormap(display); 2769 2770 /* Add a transparent entry. */ 2771 png_create_colormap_entry(display, cmap_entries, 255, 255, 2772 255, 0, P_sRGB); 2773 2774 /* This is stored as the background index for the processing 2775 * algorithm. 2776 */ 2777 background_index = cmap_entries++; 2778 2779 /* Add 27 r,g,b entries each with alpha 0.5. */ 2780 for (r=0; r<256; r = (r << 1) | 0x7f) 2781 { 2782 png_uint_32 g; 2783 2784 for (g=0; g<256; g = (g << 1) | 0x7f) 2785 { 2786 png_uint_32 b; 2787 2788 /* This generates components with the values 0, 127 and 2789 * 255 2790 */ 2791 for (b=0; b<256; b = (b << 1) | 0x7f) 2792 png_create_colormap_entry(display, cmap_entries++, 2793 r, g, b, 128, P_sRGB); 2794 } 2795 } 2796 2797 expand_tRNS = 1; 2798 output_processing = PNG_CMAP_RGB_ALPHA; 2799 } 2800 2801 else 2802 { 2803 /* Alpha/transparency must be removed. The background must 2804 * exist in the color map (achieved by setting adding it after 2805 * the 666 color-map). If the standard processing code will 2806 * pick up this entry automatically that's all that is 2807 * required; libpng can be called to do the background 2808 * processing. 2809 */ 2810 unsigned int sample_size = 2811 PNG_IMAGE_SAMPLE_SIZE(output_format); 2812 png_uint_32 r, g, b; /* sRGB background */ 2813 2814 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries) 2815 png_error(png_ptr, "rgb-alpha color-map: too few entries"); 2816 2817 cmap_entries = make_rgb_colormap(display); 2818 2819 png_create_colormap_entry(display, cmap_entries, back_r, 2820 back_g, back_b, 0/*unused*/, output_encoding); 2821 2822 if (output_encoding == P_LINEAR) 2823 { 2824 r = PNG_sRGB_FROM_LINEAR(back_r * 255); 2825 g = PNG_sRGB_FROM_LINEAR(back_g * 255); 2826 b = PNG_sRGB_FROM_LINEAR(back_b * 255); 2827 } 2828 2829 else 2830 { 2831 r = back_r; 2832 g = back_g; 2833 b = back_g; 2834 } 2835 2836 /* Compare the newly-created color-map entry with the one the 2837 * PNG_CMAP_RGB algorithm will use. If the two entries don't 2838 * match, add the new one and set this as the background 2839 * index. 2840 */ 2841 if (memcmp((png_const_bytep)display->colormap + 2842 sample_size * cmap_entries, 2843 (png_const_bytep)display->colormap + 2844 sample_size * PNG_RGB_INDEX(r,g,b), 2845 sample_size) != 0) 2846 { 2847 /* The background color must be added. */ 2848 background_index = cmap_entries++; 2849 2850 /* Add 27 r,g,b entries each with created by composing with 2851 * the background at alpha 0.5. 2852 */ 2853 for (r=0; r<256; r = (r << 1) | 0x7f) 2854 { 2855 for (g=0; g<256; g = (g << 1) | 0x7f) 2856 { 2857 /* This generates components with the values 0, 127 2858 * and 255 2859 */ 2860 for (b=0; b<256; b = (b << 1) | 0x7f) 2861 png_create_colormap_entry(display, cmap_entries++, 2862 png_colormap_compose(display, r, P_sRGB, 128, 2863 back_r, output_encoding), 2864 png_colormap_compose(display, g, P_sRGB, 128, 2865 back_g, output_encoding), 2866 png_colormap_compose(display, b, P_sRGB, 128, 2867 back_b, output_encoding), 2868 0/*unused*/, output_encoding); 2869 } 2870 } 2871 2872 expand_tRNS = 1; 2873 output_processing = PNG_CMAP_RGB_ALPHA; 2874 } 2875 2876 else /* background color is in the standard color-map */ 2877 { 2878 png_color_16 c; 2879 2880 c.index = 0; /*unused*/ 2881 c.red = (png_uint_16)back_r; 2882 c.gray = c.green = (png_uint_16)back_g; 2883 c.blue = (png_uint_16)back_b; 2884 2885 png_set_background_fixed(png_ptr, &c, 2886 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 2887 0/*gamma: not used*/); 2888 2889 output_processing = PNG_CMAP_RGB; 2890 } 2891 } 2892 } 2893 2894 else /* no alpha or transparency in the input */ 2895 { 2896 /* Alpha in the output is irrelevant, simply map the opaque input 2897 * pixels to the 6x6x6 color-map. 2898 */ 2899 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries) 2900 png_error(png_ptr, "rgb color-map: too few entries"); 2901 2902 cmap_entries = make_rgb_colormap(display); 2903 output_processing = PNG_CMAP_RGB; 2904 } 2905 } 2906 break; 2907 2908 case PNG_COLOR_TYPE_PALETTE: 2909 /* It's already got a color-map. It may be necessary to eliminate the 2910 * tRNS entries though. 2911 */ 2912 { 2913 unsigned int num_trans = png_ptr->num_trans; 2914 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL; 2915 png_const_colorp colormap = png_ptr->palette; 2916 const int do_background = trans != NULL && 2917 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0; 2918 unsigned int i; 2919 2920 /* Just in case: */ 2921 if (trans == NULL) 2922 num_trans = 0; 2923 2924 output_processing = PNG_CMAP_NONE; 2925 data_encoding = P_FILE; /* Don't change from color-map indicies */ 2926 cmap_entries = png_ptr->num_palette; 2927 if (cmap_entries > 256) 2928 cmap_entries = 256; 2929 2930 if (cmap_entries > image->colormap_entries) 2931 png_error(png_ptr, "palette color-map: too few entries"); 2932 2933 for (i=0; i < cmap_entries; ++i) 2934 { 2935 if (do_background && i < num_trans && trans[i] < 255) 2936 { 2937 if (trans[i] == 0) 2938 png_create_colormap_entry(display, i, back_r, back_g, 2939 back_b, 0, output_encoding); 2940 2941 else 2942 { 2943 /* Must compose the PNG file color in the color-map entry 2944 * on the sRGB color in 'back'. 2945 */ 2946 png_create_colormap_entry(display, i, 2947 png_colormap_compose(display, colormap[i].red, P_FILE, 2948 trans[i], back_r, output_encoding), 2949 png_colormap_compose(display, colormap[i].green, P_FILE, 2950 trans[i], back_g, output_encoding), 2951 png_colormap_compose(display, colormap[i].blue, P_FILE, 2952 trans[i], back_b, output_encoding), 2953 output_encoding == P_LINEAR ? trans[i] * 257U : 2954 trans[i], 2955 output_encoding); 2956 } 2957 } 2958 2959 else 2960 png_create_colormap_entry(display, i, colormap[i].red, 2961 colormap[i].green, colormap[i].blue, 2962 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/); 2963 } 2964 2965 /* The PNG data may have indicies packed in fewer than 8 bits, it 2966 * must be expanded if so. 2967 */ 2968 if (png_ptr->bit_depth < 8) 2969 png_set_packing(png_ptr); 2970 } 2971 break; 2972 2973 default: 2974 png_error(png_ptr, "invalid PNG color type"); 2975 /*NOT REACHED*/ 2976 break; 2977 } 2978 2979 /* Now deal with the output processing */ 2980 if (expand_tRNS && png_ptr->num_trans > 0 && 2981 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0) 2982 png_set_tRNS_to_alpha(png_ptr); 2983 2984 switch (data_encoding) 2985 { 2986 default: 2987 png_error(png_ptr, "bad data option (internal error)"); 2988 break; 2989 2990 case P_sRGB: 2991 /* Change to 8-bit sRGB */ 2992 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB); 2993 /* FALL THROUGH */ 2994 2995 case P_FILE: 2996 if (png_ptr->bit_depth > 8) 2997 png_set_scale_16(png_ptr); 2998 break; 2999 } 3000 3001 if (cmap_entries > 256 || cmap_entries > image->colormap_entries) 3002 png_error(png_ptr, "color map overflow (BAD internal error)"); 3003 3004 image->colormap_entries = cmap_entries; 3005 3006 /* Double check using the recorded background index */ 3007 switch (output_processing) 3008 { 3009 case PNG_CMAP_NONE: 3010 if (background_index != PNG_CMAP_NONE_BACKGROUND) 3011 goto bad_background; 3012 break; 3013 3014 case PNG_CMAP_GA: 3015 if (background_index != PNG_CMAP_GA_BACKGROUND) 3016 goto bad_background; 3017 break; 3018 3019 case PNG_CMAP_TRANS: 3020 if (background_index >= cmap_entries || 3021 background_index != PNG_CMAP_TRANS_BACKGROUND) 3022 goto bad_background; 3023 break; 3024 3025 case PNG_CMAP_RGB: 3026 if (background_index != PNG_CMAP_RGB_BACKGROUND) 3027 goto bad_background; 3028 break; 3029 3030 case PNG_CMAP_RGB_ALPHA: 3031 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND) 3032 goto bad_background; 3033 break; 3034 3035 default: 3036 png_error(png_ptr, "bad processing option (internal error)"); 3037 3038 bad_background: 3039 png_error(png_ptr, "bad background index (internal error)"); 3040 } 3041 3042 display->colormap_processing = output_processing; 3043 3044 return 1/*ok*/; 3045 } 3046 3047 /* The final part of the color-map read called from png_image_finish_read. */ 3048 static int 3049 png_image_read_and_map(png_voidp argument) 3050 { 3051 png_image_read_control *display = png_voidcast(png_image_read_control*, 3052 argument); 3053 png_imagep image = display->image; 3054 png_structrp png_ptr = image->opaque->png_ptr; 3055 int passes; 3056 3057 /* Called when the libpng data must be transformed into the color-mapped 3058 * form. There is a local row buffer in display->local and this routine must 3059 * do the interlace handling. 3060 */ 3061 switch (png_ptr->interlaced) 3062 { 3063 case PNG_INTERLACE_NONE: 3064 passes = 1; 3065 break; 3066 3067 case PNG_INTERLACE_ADAM7: 3068 passes = PNG_INTERLACE_ADAM7_PASSES; 3069 break; 3070 3071 default: 3072 png_error(png_ptr, "unknown interlace type"); 3073 } 3074 3075 { 3076 png_uint_32 height = image->height; 3077 png_uint_32 width = image->width; 3078 int proc = display->colormap_processing; 3079 png_bytep first_row = png_voidcast(png_bytep, display->first_row); 3080 ptrdiff_t step_row = display->row_bytes; 3081 int pass; 3082 3083 for (pass = 0; pass < passes; ++pass) 3084 { 3085 unsigned int startx, stepx, stepy; 3086 png_uint_32 y; 3087 3088 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3089 { 3090 /* The row may be empty for a short image: */ 3091 if (PNG_PASS_COLS(width, pass) == 0) 3092 continue; 3093 3094 startx = PNG_PASS_START_COL(pass); 3095 stepx = PNG_PASS_COL_OFFSET(pass); 3096 y = PNG_PASS_START_ROW(pass); 3097 stepy = PNG_PASS_ROW_OFFSET(pass); 3098 } 3099 3100 else 3101 { 3102 y = 0; 3103 startx = 0; 3104 stepx = stepy = 1; 3105 } 3106 3107 for (; y<height; y += stepy) 3108 { 3109 png_bytep inrow = png_voidcast(png_bytep, display->local_row); 3110 png_bytep outrow = first_row + y * step_row; 3111 png_const_bytep end_row = outrow + width; 3112 3113 /* Read read the libpng data into the temporary buffer. */ 3114 png_read_row(png_ptr, inrow, NULL); 3115 3116 /* Now process the row according to the processing option, note 3117 * that the caller verifies that the format of the libpng output 3118 * data is as required. 3119 */ 3120 outrow += startx; 3121 switch (proc) 3122 { 3123 case PNG_CMAP_GA: 3124 for (; outrow < end_row; outrow += stepx) 3125 { 3126 /* The data is always in the PNG order */ 3127 unsigned int gray = *inrow++; 3128 unsigned int alpha = *inrow++; 3129 unsigned int entry; 3130 3131 /* NOTE: this code is copied as a comment in 3132 * make_ga_colormap above. Please update the 3133 * comment if you change this code! 3134 */ 3135 if (alpha > 229) /* opaque */ 3136 { 3137 entry = (231 * gray + 128) >> 8; 3138 } 3139 else if (alpha < 26) /* transparent */ 3140 { 3141 entry = 231; 3142 } 3143 else /* partially opaque */ 3144 { 3145 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray); 3146 } 3147 3148 *outrow = (png_byte)entry; 3149 } 3150 break; 3151 3152 case PNG_CMAP_TRANS: 3153 for (; outrow < end_row; outrow += stepx) 3154 { 3155 png_byte gray = *inrow++; 3156 png_byte alpha = *inrow++; 3157 3158 if (alpha == 0) 3159 *outrow = PNG_CMAP_TRANS_BACKGROUND; 3160 3161 else if (gray != PNG_CMAP_TRANS_BACKGROUND) 3162 *outrow = gray; 3163 3164 else 3165 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1); 3166 } 3167 break; 3168 3169 case PNG_CMAP_RGB: 3170 for (; outrow < end_row; outrow += stepx) 3171 { 3172 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]); 3173 inrow += 3; 3174 } 3175 break; 3176 3177 case PNG_CMAP_RGB_ALPHA: 3178 for (; outrow < end_row; outrow += stepx) 3179 { 3180 unsigned int alpha = inrow[3]; 3181 3182 /* Because the alpha entries only hold alpha==0.5 values 3183 * split the processing at alpha==0.25 (64) and 0.75 3184 * (196). 3185 */ 3186 3187 if (alpha >= 196) 3188 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], 3189 inrow[2]); 3190 3191 else if (alpha < 64) 3192 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND; 3193 3194 else 3195 { 3196 /* Likewise there are three entries for each of r, g 3197 * and b. We could select the entry by popcount on 3198 * the top two bits on those architectures that 3199 * support it, this is what the code below does, 3200 * crudely. 3201 */ 3202 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1; 3203 3204 /* Here are how the values map: 3205 * 3206 * 0x00 .. 0x3f -> 0 3207 * 0x40 .. 0xbf -> 1 3208 * 0xc0 .. 0xff -> 2 3209 * 3210 * So, as above with the explicit alpha checks, the 3211 * breakpoints are at 64 and 196. 3212 */ 3213 if (inrow[0] & 0x80) back_i += 9; /* red */ 3214 if (inrow[0] & 0x40) back_i += 9; 3215 if (inrow[0] & 0x80) back_i += 3; /* green */ 3216 if (inrow[0] & 0x40) back_i += 3; 3217 if (inrow[0] & 0x80) back_i += 1; /* blue */ 3218 if (inrow[0] & 0x40) back_i += 1; 3219 3220 *outrow = (png_byte)back_i; 3221 } 3222 3223 inrow += 4; 3224 } 3225 break; 3226 3227 default: 3228 break; 3229 } 3230 } 3231 } 3232 } 3233 3234 return 1; 3235 } 3236 3237 static int 3238 png_image_read_colormapped(png_voidp argument) 3239 { 3240 png_image_read_control *display = png_voidcast(png_image_read_control*, 3241 argument); 3242 png_imagep image = display->image; 3243 png_controlp control = image->opaque; 3244 png_structrp png_ptr = control->png_ptr; 3245 png_inforp info_ptr = control->info_ptr; 3246 3247 int passes = 0; /* As a flag */ 3248 3249 PNG_SKIP_CHUNKS(png_ptr); 3250 3251 /* Update the 'info' structure and make sure the result is as required; first 3252 * make sure to turn on the interlace handling if it will be required 3253 * (because it can't be turned on *after* the call to png_read_update_info!) 3254 */ 3255 if (display->colormap_processing == PNG_CMAP_NONE) 3256 passes = png_set_interlace_handling(png_ptr); 3257 3258 png_read_update_info(png_ptr, info_ptr); 3259 3260 /* The expected output can be deduced from the colormap_processing option. */ 3261 switch (display->colormap_processing) 3262 { 3263 case PNG_CMAP_NONE: 3264 /* Output must be one channel and one byte per pixel, the output 3265 * encoding can be anything. 3266 */ 3267 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE || 3268 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) && 3269 info_ptr->bit_depth == 8) 3270 break; 3271 3272 goto bad_output; 3273 3274 case PNG_CMAP_TRANS: 3275 case PNG_CMAP_GA: 3276 /* Output must be two channels and the 'G' one must be sRGB, the latter 3277 * can be checked with an exact number because it should have been set 3278 * to this number above! 3279 */ 3280 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA && 3281 info_ptr->bit_depth == 8 && 3282 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3283 image->colormap_entries == 256) 3284 break; 3285 3286 goto bad_output; 3287 3288 case PNG_CMAP_RGB: 3289 /* Output must be 8-bit sRGB encoded RGB */ 3290 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB && 3291 info_ptr->bit_depth == 8 && 3292 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3293 image->colormap_entries == 216) 3294 break; 3295 3296 goto bad_output; 3297 3298 case PNG_CMAP_RGB_ALPHA: 3299 /* Output must be 8-bit sRGB encoded RGBA */ 3300 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA && 3301 info_ptr->bit_depth == 8 && 3302 png_ptr->screen_gamma == PNG_GAMMA_sRGB && 3303 image->colormap_entries == 244 /* 216 + 1 + 27 */) 3304 break; 3305 3306 /* goto bad_output; */ 3307 /* FALL THROUGH */ 3308 3309 default: 3310 bad_output: 3311 png_error(png_ptr, "bad color-map processing (internal error)"); 3312 } 3313 3314 /* Now read the rows. Do this here if it is possible to read directly into 3315 * the output buffer, otherwise allocate a local row buffer of the maximum 3316 * size libpng requires and call the relevant processing routine safely. 3317 */ 3318 { 3319 png_voidp first_row = display->buffer; 3320 ptrdiff_t row_bytes = display->row_stride; 3321 3322 /* The following expression is designed to work correctly whether it gives 3323 * a signed or an unsigned result. 3324 */ 3325 if (row_bytes < 0) 3326 { 3327 char *ptr = png_voidcast(char*, first_row); 3328 ptr += (image->height-1) * (-row_bytes); 3329 first_row = png_voidcast(png_voidp, ptr); 3330 } 3331 3332 display->first_row = first_row; 3333 display->row_bytes = row_bytes; 3334 } 3335 3336 if (passes == 0) 3337 { 3338 int result; 3339 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 3340 3341 display->local_row = row; 3342 result = png_safe_execute(image, png_image_read_and_map, display); 3343 display->local_row = NULL; 3344 png_free(png_ptr, row); 3345 3346 return result; 3347 } 3348 3349 else 3350 { 3351 png_alloc_size_t row_bytes = display->row_bytes; 3352 3353 while (--passes >= 0) 3354 { 3355 png_uint_32 y = image->height; 3356 png_bytep row = png_voidcast(png_bytep, display->first_row); 3357 3358 while (y-- > 0) 3359 { 3360 png_read_row(png_ptr, row, NULL); 3361 row += row_bytes; 3362 } 3363 } 3364 3365 return 1; 3366 } 3367 } 3368 3369 /* Just the row reading part of png_image_read. */ 3370 static int 3371 png_image_read_composite(png_voidp argument) 3372 { 3373 png_image_read_control *display = png_voidcast(png_image_read_control*, 3374 argument); 3375 png_imagep image = display->image; 3376 png_structrp png_ptr = image->opaque->png_ptr; 3377 int passes; 3378 3379 switch (png_ptr->interlaced) 3380 { 3381 case PNG_INTERLACE_NONE: 3382 passes = 1; 3383 break; 3384 3385 case PNG_INTERLACE_ADAM7: 3386 passes = PNG_INTERLACE_ADAM7_PASSES; 3387 break; 3388 3389 default: 3390 png_error(png_ptr, "unknown interlace type"); 3391 } 3392 3393 { 3394 png_uint_32 height = image->height; 3395 png_uint_32 width = image->width; 3396 ptrdiff_t step_row = display->row_bytes; 3397 unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1; 3398 int pass; 3399 3400 for (pass = 0; pass < passes; ++pass) 3401 { 3402 unsigned int startx, stepx, stepy; 3403 png_uint_32 y; 3404 3405 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3406 { 3407 /* The row may be empty for a short image: */ 3408 if (PNG_PASS_COLS(width, pass) == 0) 3409 continue; 3410 3411 startx = PNG_PASS_START_COL(pass) * channels; 3412 stepx = PNG_PASS_COL_OFFSET(pass) * channels; 3413 y = PNG_PASS_START_ROW(pass); 3414 stepy = PNG_PASS_ROW_OFFSET(pass); 3415 } 3416 3417 else 3418 { 3419 y = 0; 3420 startx = 0; 3421 stepx = channels; 3422 stepy = 1; 3423 } 3424 3425 for (; y<height; y += stepy) 3426 { 3427 png_bytep inrow = png_voidcast(png_bytep, display->local_row); 3428 png_bytep outrow; 3429 png_const_bytep end_row; 3430 3431 /* Read the row, which is packed: */ 3432 png_read_row(png_ptr, inrow, NULL); 3433 3434 outrow = png_voidcast(png_bytep, display->first_row); 3435 outrow += y * step_row; 3436 end_row = outrow + width * channels; 3437 3438 /* Now do the composition on each pixel in this row. */ 3439 outrow += startx; 3440 for (; outrow < end_row; outrow += stepx) 3441 { 3442 png_byte alpha = inrow[channels]; 3443 3444 if (alpha > 0) /* else no change to the output */ 3445 { 3446 unsigned int c; 3447 3448 for (c=0; c<channels; ++c) 3449 { 3450 png_uint_32 component = inrow[c]; 3451 3452 if (alpha < 255) /* else just use component */ 3453 { 3454 /* This is PNG_OPTIMIZED_ALPHA, the component value 3455 * is a linear 8-bit value. Combine this with the 3456 * current outrow[c] value which is sRGB encoded. 3457 * Arithmetic here is 16-bits to preserve the output 3458 * values correctly. 3459 */ 3460 component *= 257*255; /* =65535 */ 3461 component += (255-alpha)*png_sRGB_table[outrow[c]]; 3462 3463 /* So 'component' is scaled by 255*65535 and is 3464 * therefore appropriate for the sRGB to linear 3465 * conversion table. 3466 */ 3467 component = PNG_sRGB_FROM_LINEAR(component); 3468 } 3469 3470 outrow[c] = (png_byte)component; 3471 } 3472 } 3473 3474 inrow += channels+1; /* components and alpha channel */ 3475 } 3476 } 3477 } 3478 } 3479 3480 return 1; 3481 } 3482 3483 /* The do_local_background case; called when all the following transforms are to 3484 * be done: 3485 * 3486 * PNG_RGB_TO_GRAY 3487 * PNG_COMPOSITE 3488 * PNG_GAMMA 3489 * 3490 * This is a work-round for the fact that both the PNG_RGB_TO_GRAY and 3491 * PNG_COMPOSITE code performs gamma correction, so we get double gamma 3492 * correction. The fix-up is to prevent the PNG_COMPOSITE operation happening 3493 * inside libpng, so this routine sees an 8 or 16-bit gray+alpha row and handles 3494 * the removal or pre-multiplication of the alpha channel. 3495 */ 3496 static int 3497 png_image_read_background(png_voidp argument) 3498 { 3499 png_image_read_control *display = png_voidcast(png_image_read_control*, 3500 argument); 3501 png_imagep image = display->image; 3502 png_structrp png_ptr = image->opaque->png_ptr; 3503 png_inforp info_ptr = image->opaque->info_ptr; 3504 png_uint_32 height = image->height; 3505 png_uint_32 width = image->width; 3506 int pass, passes; 3507 3508 /* Double check the convoluted logic below. We expect to get here with 3509 * libpng doing rgb to gray and gamma correction but background processing 3510 * left to the png_image_read_background function. The rows libpng produce 3511 * might be 8 or 16-bit but should always have two channels; gray plus alpha. 3512 */ 3513 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0) 3514 png_error(png_ptr, "lost rgb to gray"); 3515 3516 if ((png_ptr->transformations & PNG_COMPOSE) != 0) 3517 png_error(png_ptr, "unexpected compose"); 3518 3519 if (png_get_channels(png_ptr, info_ptr) != 2) 3520 png_error(png_ptr, "lost/gained channels"); 3521 3522 /* Expect the 8-bit case to always remove the alpha channel */ 3523 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 && 3524 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0) 3525 png_error(png_ptr, "unexpected 8-bit transformation"); 3526 3527 switch (png_ptr->interlaced) 3528 { 3529 case PNG_INTERLACE_NONE: 3530 passes = 1; 3531 break; 3532 3533 case PNG_INTERLACE_ADAM7: 3534 passes = PNG_INTERLACE_ADAM7_PASSES; 3535 break; 3536 3537 default: 3538 png_error(png_ptr, "unknown interlace type"); 3539 } 3540 3541 /* Use direct access to info_ptr here because otherwise the simplified API 3542 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is 3543 * checking the value after libpng expansions, not the original value in the 3544 * PNG. 3545 */ 3546 switch (info_ptr->bit_depth) 3547 { 3548 default: 3549 png_error(png_ptr, "unexpected bit depth"); 3550 break; 3551 3552 case 8: 3553 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is 3554 * to be removed by composing on a background: either the row if 3555 * display->background is NULL or display->background->green if not. 3556 * Unlike the code above ALPHA_OPTIMIZED has *not* been done. 3557 */ 3558 { 3559 png_bytep first_row = png_voidcast(png_bytep, display->first_row); 3560 ptrdiff_t step_row = display->row_bytes; 3561 3562 for (pass = 0; pass < passes; ++pass) 3563 { 3564 png_bytep row = png_voidcast(png_bytep, 3565 display->first_row); 3566 unsigned int startx, stepx, stepy; 3567 png_uint_32 y; 3568 3569 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3570 { 3571 /* The row may be empty for a short image: */ 3572 if (PNG_PASS_COLS(width, pass) == 0) 3573 continue; 3574 3575 startx = PNG_PASS_START_COL(pass); 3576 stepx = PNG_PASS_COL_OFFSET(pass); 3577 y = PNG_PASS_START_ROW(pass); 3578 stepy = PNG_PASS_ROW_OFFSET(pass); 3579 } 3580 3581 else 3582 { 3583 y = 0; 3584 startx = 0; 3585 stepx = stepy = 1; 3586 } 3587 3588 if (display->background == NULL) 3589 { 3590 for (; y<height; y += stepy) 3591 { 3592 png_bytep inrow = png_voidcast(png_bytep, 3593 display->local_row); 3594 png_bytep outrow = first_row + y * step_row; 3595 png_const_bytep end_row = outrow + width; 3596 3597 /* Read the row, which is packed: */ 3598 png_read_row(png_ptr, inrow, NULL); 3599 3600 /* Now do the composition on each pixel in this row. */ 3601 outrow += startx; 3602 for (; outrow < end_row; outrow += stepx) 3603 { 3604 png_byte alpha = inrow[1]; 3605 3606 if (alpha > 0) /* else no change to the output */ 3607 { 3608 png_uint_32 component = inrow[0]; 3609 3610 if (alpha < 255) /* else just use component */ 3611 { 3612 /* Since PNG_OPTIMIZED_ALPHA was not set it is 3613 * necessary to invert the sRGB transfer 3614 * function and multiply the alpha out. 3615 */ 3616 component = png_sRGB_table[component] * alpha; 3617 component += png_sRGB_table[outrow[0]] * 3618 (255-alpha); 3619 component = PNG_sRGB_FROM_LINEAR(component); 3620 } 3621 3622 outrow[0] = (png_byte)component; 3623 } 3624 3625 inrow += 2; /* gray and alpha channel */ 3626 } 3627 } 3628 } 3629 3630 else /* constant background value */ 3631 { 3632 png_byte background8 = display->background->green; 3633 png_uint_16 background = png_sRGB_table[background8]; 3634 3635 for (; y<height; y += stepy) 3636 { 3637 png_bytep inrow = png_voidcast(png_bytep, 3638 display->local_row); 3639 png_bytep outrow = first_row + y * step_row; 3640 png_const_bytep end_row = outrow + width; 3641 3642 /* Read the row, which is packed: */ 3643 png_read_row(png_ptr, inrow, NULL); 3644 3645 /* Now do the composition on each pixel in this row. */ 3646 outrow += startx; 3647 for (; outrow < end_row; outrow += stepx) 3648 { 3649 png_byte alpha = inrow[1]; 3650 3651 if (alpha > 0) /* else use background */ 3652 { 3653 png_uint_32 component = inrow[0]; 3654 3655 if (alpha < 255) /* else just use component */ 3656 { 3657 component = png_sRGB_table[component] * alpha; 3658 component += background * (255-alpha); 3659 component = PNG_sRGB_FROM_LINEAR(component); 3660 } 3661 3662 outrow[0] = (png_byte)component; 3663 } 3664 3665 else 3666 outrow[0] = background8; 3667 3668 inrow += 2; /* gray and alpha channel */ 3669 } 3670 3671 row += display->row_bytes; 3672 } 3673 } 3674 } 3675 } 3676 break; 3677 3678 case 16: 3679 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must 3680 * still be done and, maybe, the alpha channel removed. This code also 3681 * handles the alpha-first option. 3682 */ 3683 { 3684 png_uint_16p first_row = png_voidcast(png_uint_16p, 3685 display->first_row); 3686 /* The division by two is safe because the caller passed in a 3687 * stride which was multiplied by 2 (below) to get row_bytes. 3688 */ 3689 ptrdiff_t step_row = display->row_bytes / 2; 3690 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0; 3691 unsigned int outchannels = 1+preserve_alpha; 3692 int swap_alpha = 0; 3693 3694 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED 3695 if (preserve_alpha && (image->format & PNG_FORMAT_FLAG_AFIRST)) 3696 swap_alpha = 1; 3697 # endif 3698 3699 for (pass = 0; pass < passes; ++pass) 3700 { 3701 unsigned int startx, stepx, stepy; 3702 png_uint_32 y; 3703 3704 /* The 'x' start and step are adjusted to output components here. 3705 */ 3706 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7) 3707 { 3708 /* The row may be empty for a short image: */ 3709 if (PNG_PASS_COLS(width, pass) == 0) 3710 continue; 3711 3712 startx = PNG_PASS_START_COL(pass) * outchannels; 3713 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels; 3714 y = PNG_PASS_START_ROW(pass); 3715 stepy = PNG_PASS_ROW_OFFSET(pass); 3716 } 3717 3718 else 3719 { 3720 y = 0; 3721 startx = 0; 3722 stepx = outchannels; 3723 stepy = 1; 3724 } 3725 3726 for (; y<height; y += stepy) 3727 { 3728 png_const_uint_16p inrow; 3729 png_uint_16p outrow = first_row + y*step_row; 3730 png_uint_16p end_row = outrow + width * outchannels; 3731 3732 /* Read the row, which is packed: */ 3733 png_read_row(png_ptr, png_voidcast(png_bytep, 3734 display->local_row), NULL); 3735 inrow = png_voidcast(png_const_uint_16p, display->local_row); 3736 3737 /* Now do the pre-multiplication on each pixel in this row. 3738 */ 3739 outrow += startx; 3740 for (; outrow < end_row; outrow += stepx) 3741 { 3742 png_uint_32 component = inrow[0]; 3743 png_uint_16 alpha = inrow[1]; 3744 3745 if (alpha > 0) /* else 0 */ 3746 { 3747 if (alpha < 65535) /* else just use component */ 3748 { 3749 component *= alpha; 3750 component += 32767; 3751 component /= 65535; 3752 } 3753 } 3754 3755 else 3756 component = 0; 3757 3758 outrow[swap_alpha] = (png_uint_16)component; 3759 if (preserve_alpha) 3760 outrow[1 ^ swap_alpha] = alpha; 3761 3762 inrow += 2; /* components and alpha channel */ 3763 } 3764 } 3765 } 3766 } 3767 break; 3768 } 3769 3770 return 1; 3771 } 3772 3773 /* The guts of png_image_finish_read as a png_safe_execute callback. */ 3774 static int 3775 png_image_read_direct(png_voidp argument) 3776 { 3777 png_image_read_control *display = png_voidcast(png_image_read_control*, 3778 argument); 3779 png_imagep image = display->image; 3780 png_structrp png_ptr = image->opaque->png_ptr; 3781 png_inforp info_ptr = image->opaque->info_ptr; 3782 3783 png_uint_32 format = image->format; 3784 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0; 3785 int do_local_compose = 0; 3786 int do_local_background = 0; /* to avoid double gamma correction bug */ 3787 int passes = 0; 3788 3789 /* Add transforms to ensure the correct output format is produced then check 3790 * that the required implementation support is there. Always expand; always 3791 * need 8 bits minimum, no palette and expanded tRNS. 3792 */ 3793 png_set_expand(png_ptr); 3794 3795 /* Now check the format to see if it was modified. */ 3796 { 3797 png_uint_32 base_format = png_image_format(png_ptr) & 3798 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */; 3799 png_uint_32 change = format ^ base_format; 3800 png_fixed_point output_gamma; 3801 int mode; /* alpha mode */ 3802 3803 /* Do this first so that we have a record if rgb to gray is happening. */ 3804 if (change & PNG_FORMAT_FLAG_COLOR) 3805 { 3806 /* gray<->color transformation required. */ 3807 if (format & PNG_FORMAT_FLAG_COLOR) 3808 png_set_gray_to_rgb(png_ptr); 3809 3810 else 3811 { 3812 /* libpng can't do both rgb to gray and 3813 * background/pre-multiplication if there is also significant gamma 3814 * correction, because both operations require linear colors and 3815 * the code only supports one transform doing the gamma correction. 3816 * Handle this by doing the pre-multiplication or background 3817 * operation in this code, if necessary. 3818 * 3819 * TODO: fix this by rewriting pngrtran.c (!) 3820 * 3821 * For the moment (given that fixing this in pngrtran.c is an 3822 * enormous change) 'do_local_background' is used to indicate that 3823 * the problem exists. 3824 */ 3825 if (base_format & PNG_FORMAT_FLAG_ALPHA) 3826 do_local_background = 1/*maybe*/; 3827 3828 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, 3829 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT); 3830 } 3831 3832 change &= ~PNG_FORMAT_FLAG_COLOR; 3833 } 3834 3835 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise. 3836 */ 3837 { 3838 png_fixed_point input_gamma_default; 3839 3840 if ((base_format & PNG_FORMAT_FLAG_LINEAR) && 3841 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0) 3842 input_gamma_default = PNG_GAMMA_LINEAR; 3843 else 3844 input_gamma_default = PNG_DEFAULT_sRGB; 3845 3846 /* Call png_set_alpha_mode to set the default for the input gamma; the 3847 * output gamma is set by a second call below. 3848 */ 3849 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default); 3850 } 3851 3852 if (linear) 3853 { 3854 /* If there *is* an alpha channel in the input it must be multiplied 3855 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG. 3856 */ 3857 if (base_format & PNG_FORMAT_FLAG_ALPHA) 3858 mode = PNG_ALPHA_STANDARD; /* associated alpha */ 3859 3860 else 3861 mode = PNG_ALPHA_PNG; 3862 3863 output_gamma = PNG_GAMMA_LINEAR; 3864 } 3865 3866 else 3867 { 3868 mode = PNG_ALPHA_PNG; 3869 output_gamma = PNG_DEFAULT_sRGB; 3870 } 3871 3872 /* If 'do_local_background' is set check for the presence of gamma 3873 * correction; this is part of the work-round for the libpng bug 3874 * described above. 3875 * 3876 * TODO: fix libpng and remove this. 3877 */ 3878 if (do_local_background) 3879 { 3880 png_fixed_point gtest; 3881 3882 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for 3883 * gamma correction, the screen gamma hasn't been set on png_struct 3884 * yet; it's set below. png_struct::gamma, however, is set to the 3885 * final value. 3886 */ 3887 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma, 3888 PNG_FP_1) && !png_gamma_significant(gtest)) 3889 do_local_background = 0; 3890 3891 else if (mode == PNG_ALPHA_STANDARD) 3892 { 3893 do_local_background = 2/*required*/; 3894 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */ 3895 } 3896 3897 /* else leave as 1 for the checks below */ 3898 } 3899 3900 /* If the bit-depth changes then handle that here. */ 3901 if (change & PNG_FORMAT_FLAG_LINEAR) 3902 { 3903 if (linear /*16-bit output*/) 3904 png_set_expand_16(png_ptr); 3905 3906 else /* 8-bit output */ 3907 png_set_scale_16(png_ptr); 3908 3909 change &= ~PNG_FORMAT_FLAG_LINEAR; 3910 } 3911 3912 /* Now the background/alpha channel changes. */ 3913 if (change & PNG_FORMAT_FLAG_ALPHA) 3914 { 3915 /* Removing an alpha channel requires composition for the 8-bit 3916 * formats; for the 16-bit it is already done, above, by the 3917 * pre-multiplication and the channel just needs to be stripped. 3918 */ 3919 if (base_format & PNG_FORMAT_FLAG_ALPHA) 3920 { 3921 /* If RGB->gray is happening the alpha channel must be left and the 3922 * operation completed locally. 3923 * 3924 * TODO: fix libpng and remove this. 3925 */ 3926 if (do_local_background) 3927 do_local_background = 2/*required*/; 3928 3929 /* 16-bit output: just remove the channel */ 3930 else if (linear) /* compose on black (well, pre-multiply) */ 3931 png_set_strip_alpha(png_ptr); 3932 3933 /* 8-bit output: do an appropriate compose */ 3934 else if (display->background != NULL) 3935 { 3936 png_color_16 c; 3937 3938 c.index = 0; /*unused*/ 3939 c.red = display->background->red; 3940 c.green = display->background->green; 3941 c.blue = display->background->blue; 3942 c.gray = display->background->green; 3943 3944 /* This is always an 8-bit sRGB value, using the 'green' channel 3945 * for gray is much better than calculating the luminance here; 3946 * we can get off-by-one errors in that calculation relative to 3947 * the app expectations and that will show up in transparent 3948 * pixels. 3949 */ 3950 png_set_background_fixed(png_ptr, &c, 3951 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/, 3952 0/*gamma: not used*/); 3953 } 3954 3955 else /* compose on row: implemented below. */ 3956 { 3957 do_local_compose = 1; 3958 /* This leaves the alpha channel in the output, so it has to be 3959 * removed by the code below. Set the encoding to the 'OPTIMIZE' 3960 * one so the code only has to hack on the pixels that require 3961 * composition. 3962 */ 3963 mode = PNG_ALPHA_OPTIMIZED; 3964 } 3965 } 3966 3967 else /* output needs an alpha channel */ 3968 { 3969 /* This is tricky because it happens before the swap operation has 3970 * been accomplished; however, the swap does *not* swap the added 3971 * alpha channel (weird API), so it must be added in the correct 3972 * place. 3973 */ 3974 png_uint_32 filler; /* opaque filler */ 3975 int where; 3976 3977 if (linear) 3978 filler = 65535; 3979 3980 else 3981 filler = 255; 3982 3983 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 3984 if (format & PNG_FORMAT_FLAG_AFIRST) 3985 { 3986 where = PNG_FILLER_BEFORE; 3987 change &= ~PNG_FORMAT_FLAG_AFIRST; 3988 } 3989 3990 else 3991 # endif 3992 where = PNG_FILLER_AFTER; 3993 3994 png_set_add_alpha(png_ptr, filler, where); 3995 } 3996 3997 /* This stops the (irrelevant) call to swap_alpha below. */ 3998 change &= ~PNG_FORMAT_FLAG_ALPHA; 3999 } 4000 4001 /* Now set the alpha mode correctly; this is always done, even if there is 4002 * no alpha channel in either the input or the output because it correctly 4003 * sets the output gamma. 4004 */ 4005 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma); 4006 4007 # ifdef PNG_FORMAT_BGR_SUPPORTED 4008 if (change & PNG_FORMAT_FLAG_BGR) 4009 { 4010 /* Check only the output format; PNG is never BGR; don't do this if 4011 * the output is gray, but fix up the 'format' value in that case. 4012 */ 4013 if (format & PNG_FORMAT_FLAG_COLOR) 4014 png_set_bgr(png_ptr); 4015 4016 else 4017 format &= ~PNG_FORMAT_FLAG_BGR; 4018 4019 change &= ~PNG_FORMAT_FLAG_BGR; 4020 } 4021 # endif 4022 4023 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 4024 if (change & PNG_FORMAT_FLAG_AFIRST) 4025 { 4026 /* Only relevant if there is an alpha channel - it's particularly 4027 * important to handle this correctly because do_local_compose may 4028 * be set above and then libpng will keep the alpha channel for this 4029 * code to remove. 4030 */ 4031 if (format & PNG_FORMAT_FLAG_ALPHA) 4032 { 4033 /* Disable this if doing a local background, 4034 * TODO: remove this when local background is no longer required. 4035 */ 4036 if (do_local_background != 2) 4037 png_set_swap_alpha(png_ptr); 4038 } 4039 4040 else 4041 format &= ~PNG_FORMAT_FLAG_AFIRST; 4042 4043 change &= ~PNG_FORMAT_FLAG_AFIRST; 4044 } 4045 # endif 4046 4047 /* If the *output* is 16-bit then we need to check for a byte-swap on this 4048 * architecture. 4049 */ 4050 if (linear) 4051 { 4052 PNG_CONST png_uint_16 le = 0x0001; 4053 4054 if (*(png_const_bytep)&le) 4055 png_set_swap(png_ptr); 4056 } 4057 4058 /* If change is not now 0 some transformation is missing - error out. */ 4059 if (change) 4060 png_error(png_ptr, "png_read_image: unsupported transformation"); 4061 } 4062 4063 PNG_SKIP_CHUNKS(png_ptr); 4064 4065 /* Update the 'info' structure and make sure the result is as required; first 4066 * make sure to turn on the interlace handling if it will be required 4067 * (because it can't be turned on *after* the call to png_read_update_info!) 4068 * 4069 * TODO: remove the do_local_background fixup below. 4070 */ 4071 if (!do_local_compose && do_local_background != 2) 4072 passes = png_set_interlace_handling(png_ptr); 4073 4074 png_read_update_info(png_ptr, info_ptr); 4075 4076 { 4077 png_uint_32 info_format = 0; 4078 4079 if (info_ptr->color_type & PNG_COLOR_MASK_COLOR) 4080 info_format |= PNG_FORMAT_FLAG_COLOR; 4081 4082 if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA) 4083 { 4084 /* do_local_compose removes this channel below. */ 4085 if (!do_local_compose) 4086 { 4087 /* do_local_background does the same if required. */ 4088 if (do_local_background != 2 || 4089 (format & PNG_FORMAT_FLAG_ALPHA) != 0) 4090 info_format |= PNG_FORMAT_FLAG_ALPHA; 4091 } 4092 } 4093 4094 else if (do_local_compose) /* internal error */ 4095 png_error(png_ptr, "png_image_read: alpha channel lost"); 4096 4097 if (info_ptr->bit_depth == 16) 4098 info_format |= PNG_FORMAT_FLAG_LINEAR; 4099 4100 # ifdef PNG_FORMAT_BGR_SUPPORTED 4101 if (png_ptr->transformations & PNG_BGR) 4102 info_format |= PNG_FORMAT_FLAG_BGR; 4103 # endif 4104 4105 # ifdef PNG_FORMAT_AFIRST_SUPPORTED 4106 if (do_local_background == 2) 4107 { 4108 if (format & PNG_FORMAT_FLAG_AFIRST) 4109 info_format |= PNG_FORMAT_FLAG_AFIRST; 4110 } 4111 4112 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 || 4113 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 && 4114 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0)) 4115 { 4116 if (do_local_background == 2) 4117 png_error(png_ptr, "unexpected alpha swap transformation"); 4118 4119 info_format |= PNG_FORMAT_FLAG_AFIRST; 4120 } 4121 # endif 4122 4123 /* This is actually an internal error. */ 4124 if (info_format != format) 4125 png_error(png_ptr, "png_read_image: invalid transformations"); 4126 } 4127 4128 /* Now read the rows. If do_local_compose is set then it is necessary to use 4129 * a local row buffer. The output will be GA, RGBA or BGRA and must be 4130 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the 4131 * display acts as a flag. 4132 */ 4133 { 4134 png_voidp first_row = display->buffer; 4135 ptrdiff_t row_bytes = display->row_stride; 4136 4137 if (linear) 4138 row_bytes *= 2; 4139 4140 /* The following expression is designed to work correctly whether it gives 4141 * a signed or an unsigned result. 4142 */ 4143 if (row_bytes < 0) 4144 { 4145 char *ptr = png_voidcast(char*, first_row); 4146 ptr += (image->height-1) * (-row_bytes); 4147 first_row = png_voidcast(png_voidp, ptr); 4148 } 4149 4150 display->first_row = first_row; 4151 display->row_bytes = row_bytes; 4152 } 4153 4154 if (do_local_compose) 4155 { 4156 int result; 4157 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 4158 4159 display->local_row = row; 4160 result = png_safe_execute(image, png_image_read_composite, display); 4161 display->local_row = NULL; 4162 png_free(png_ptr, row); 4163 4164 return result; 4165 } 4166 4167 else if (do_local_background == 2) 4168 { 4169 int result; 4170 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr)); 4171 4172 display->local_row = row; 4173 result = png_safe_execute(image, png_image_read_background, display); 4174 display->local_row = NULL; 4175 png_free(png_ptr, row); 4176 4177 return result; 4178 } 4179 4180 else 4181 { 4182 png_alloc_size_t row_bytes = display->row_bytes; 4183 4184 while (--passes >= 0) 4185 { 4186 png_uint_32 y = image->height; 4187 png_bytep row = png_voidcast(png_bytep, display->first_row); 4188 4189 while (y-- > 0) 4190 { 4191 png_read_row(png_ptr, row, NULL); 4192 row += row_bytes; 4193 } 4194 } 4195 4196 return 1; 4197 } 4198 } 4199 4200 int PNGAPI 4201 png_image_finish_read(png_imagep image, png_const_colorp background, 4202 void *buffer, png_int_32 row_stride, void *colormap) 4203 { 4204 if (image != NULL && image->version == PNG_IMAGE_VERSION) 4205 { 4206 png_uint_32 check; 4207 4208 if (row_stride == 0) 4209 row_stride = PNG_IMAGE_ROW_STRIDE(*image); 4210 4211 if (row_stride < 0) 4212 check = -row_stride; 4213 4214 else 4215 check = row_stride; 4216 4217 if (image->opaque != NULL && buffer != NULL && 4218 check >= PNG_IMAGE_ROW_STRIDE(*image)) 4219 { 4220 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 || 4221 (image->colormap_entries > 0 && colormap != NULL)) 4222 { 4223 int result; 4224 png_image_read_control display; 4225 4226 memset(&display, 0, (sizeof display)); 4227 display.image = image; 4228 display.buffer = buffer; 4229 display.row_stride = row_stride; 4230 display.colormap = colormap; 4231 display.background = background; 4232 display.local_row = NULL; 4233 4234 /* Choose the correct 'end' routine; for the color-map case all the 4235 * setup has already been done. 4236 */ 4237 if (image->format & PNG_FORMAT_FLAG_COLORMAP) 4238 result = 4239 png_safe_execute(image, png_image_read_colormap, &display) && 4240 png_safe_execute(image, png_image_read_colormapped, &display); 4241 4242 else 4243 result = 4244 png_safe_execute(image, png_image_read_direct, &display); 4245 4246 png_image_free(image); 4247 return result; 4248 } 4249 4250 else 4251 return png_image_error(image, 4252 "png_image_finish_read[color-map]: no color-map"); 4253 } 4254 4255 else 4256 return png_image_error(image, 4257 "png_image_finish_read: invalid argument"); 4258 } 4259 4260 else if (image != NULL) 4261 return png_image_error(image, 4262 "png_image_finish_read: damaged PNG_IMAGE_VERSION"); 4263 4264 return 0; 4265 } 4266 4267 #endif /* PNG_SIMPLIFIED_READ_SUPPORTED */ 4268 #endif /* PNG_READ_SUPPORTED */ 4269