1 /*--------------------------------------------------------------------------- 2 3 rpng2 - progressive-model PNG display program readpng2.c 4 5 --------------------------------------------------------------------------- 6 7 Copyright (c) 1998-2007 Greg Roelofs. All rights reserved. 8 9 This software is provided "as is," without warranty of any kind, 10 express or implied. In no event shall the author or contributors 11 be held liable for any damages arising in any way from the use of 12 this software. 13 14 The contents of this file are DUAL-LICENSED. You may modify and/or 15 redistribute this software according to the terms of one of the 16 following two licenses (at your option): 17 18 19 LICENSE 1 ("BSD-like with advertising clause"): 20 21 Permission is granted to anyone to use this software for any purpose, 22 including commercial applications, and to alter it and redistribute 23 it freely, subject to the following restrictions: 24 25 1. Redistributions of source code must retain the above copyright 26 notice, disclaimer, and this list of conditions. 27 2. Redistributions in binary form must reproduce the above copyright 28 notice, disclaimer, and this list of conditions in the documenta- 29 tion and/or other materials provided with the distribution. 30 3. All advertising materials mentioning features or use of this 31 software must display the following acknowledgment: 32 33 This product includes software developed by Greg Roelofs 34 and contributors for the book, "PNG: The Definitive Guide," 35 published by O'Reilly and Associates. 36 37 38 LICENSE 2 (GNU GPL v2 or later): 39 40 This program is free software; you can redistribute it and/or modify 41 it under the terms of the GNU General Public License as published by 42 the Free Software Foundation; either version 2 of the License, or 43 (at your option) any later version. 44 45 This program is distributed in the hope that it will be useful, 46 but WITHOUT ANY WARRANTY; without even the implied warranty of 47 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 48 GNU General Public License for more details. 49 50 You should have received a copy of the GNU General Public License 51 along with this program; if not, write to the Free Software Foundation, 52 Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 53 54 ---------------------------------------------------------------------------*/ 55 56 57 #include <stdlib.h> /* for exit() prototype */ 58 59 #include "png.h" /* libpng header; includes zlib.h and setjmp.h */ 60 #include "readpng2.h" /* typedefs, common macros, public prototypes */ 61 62 63 /* local prototypes */ 64 65 static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr); 66 static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row, 67 png_uint_32 row_num, int pass); 68 static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr); 69 static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg); 70 71 72 73 74 void readpng2_version_info(void) 75 { 76 #if defined(PNG_ASSEMBLER_CODE_SUPPORTED) && \ 77 (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__)) && \ 78 defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200) 79 /* 80 * WARNING: This preprocessor approach means that the following code 81 * cannot be used with a libpng DLL older than 1.2.0--the 82 * compiled-in symbols for the new functions will not exist. 83 * (Could use dlopen() and dlsym() on Unix and corresponding 84 * calls for Windows, but not portable...) 85 */ 86 { 87 int mmxsupport = png_mmx_support(); 88 if (mmxsupport < 0) 89 fprintf(stderr, " Compiled with libpng %s; using libpng %s " 90 "without MMX support.\n", PNG_LIBPNG_VER_STRING, png_libpng_ver); 91 else { 92 int compilerID; 93 png_uint_32 mmx_mask = png_get_mmx_flagmask( 94 PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID); 95 96 fprintf(stderr, " Compiled with libpng %s; using libpng %s " 97 "with MMX support\n (%s version).", PNG_LIBPNG_VER_STRING, 98 png_libpng_ver, compilerID == 1? "MSVC++" : 99 (compilerID == 2? "GNU C" : "unknown")); 100 fprintf(stderr, " Processor (x86%s) %s MMX instructions.\n", 101 #if defined(__x86_64__) 102 "_64", 103 #else 104 "", 105 #endif 106 mmxsupport? "supports" : "does not support"); 107 if (mmxsupport > 0) { 108 int num_optims = 0; 109 110 fprintf(stderr, 111 " Potential MMX optimizations supported by libpng:\n"); 112 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_SUB) 113 ++num_optims; 114 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_UP) 115 ++num_optims; 116 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_AVG) 117 ++num_optims; 118 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_PAETH) 119 ++num_optims; 120 if (num_optims) 121 fprintf(stderr, 122 " decoding %s row filters (reading)\n", 123 (num_optims == 4)? "all non-trivial" : "some"); 124 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_COMBINE_ROW) { 125 fprintf(stderr, " combining rows (reading)\n"); 126 ++num_optims; 127 } 128 if (mmx_mask & PNG_ASM_FLAG_MMX_READ_INTERLACE) { 129 fprintf(stderr, 130 " expanding interlacing (reading)\n"); 131 ++num_optims; 132 } 133 mmx_mask &= ~( PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \ 134 | PNG_ASM_FLAG_MMX_READ_INTERLACE \ 135 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \ 136 | PNG_ASM_FLAG_MMX_READ_FILTER_UP \ 137 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \ 138 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH ); 139 if (mmx_mask) { 140 fprintf(stderr, " other (unknown)\n"); 141 ++num_optims; 142 } 143 if (num_optims == 0) 144 fprintf(stderr, " (none)\n"); 145 } 146 } 147 } 148 #else 149 fprintf(stderr, " Compiled with libpng %s; using libpng %s " 150 "without MMX support.\n", PNG_LIBPNG_VER_STRING, png_libpng_ver); 151 #endif 152 153 fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n", 154 ZLIB_VERSION, zlib_version); 155 } 156 157 158 159 160 int readpng2_check_sig(uch *sig, int num) 161 { 162 return !png_sig_cmp(sig, 0, num); 163 } 164 165 166 167 168 /* returns 0 for success, 2 for libpng problem, 4 for out of memory */ 169 170 int readpng2_init(mainprog_info *mainprog_ptr) 171 { 172 png_structp png_ptr; /* note: temporary variables! */ 173 png_infop info_ptr; 174 175 176 /* could also replace libpng warning-handler (final NULL), but no need: */ 177 178 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr, 179 readpng2_error_handler, NULL); 180 if (!png_ptr) 181 return 4; /* out of memory */ 182 183 info_ptr = png_create_info_struct(png_ptr); 184 if (!info_ptr) { 185 png_destroy_read_struct(&png_ptr, NULL, NULL); 186 return 4; /* out of memory */ 187 } 188 189 190 /* we could create a second info struct here (end_info), but it's only 191 * useful if we want to keep pre- and post-IDAT chunk info separated 192 * (mainly for PNG-aware image editors and converters) */ 193 194 195 /* setjmp() must be called in every function that calls a PNG-reading 196 * libpng function, unless an alternate error handler was installed-- 197 * but compatible error handlers must either use longjmp() themselves 198 * (as in this program) or exit immediately, so here we are: */ 199 200 if (setjmp(mainprog_ptr->jmpbuf)) { 201 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 202 return 2; 203 } 204 205 206 #ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED 207 /* prepare the reader to ignore all recognized chunks whose data won't be 208 * used, i.e., all chunks recognized by libpng except for IHDR, PLTE, IDAT, 209 * IEND, tRNS, bKGD, gAMA, and sRGB (small performance improvement) */ 210 { 211 /* These byte strings were copied from png.h. If a future libpng 212 * version recognizes more chunks, add them to this list. If a 213 * future version of readpng2.c recognizes more chunks, delete them 214 * from this list. */ 215 static const png_byte chunks_to_ignore[] = { 216 99, 72, 82, 77, '\0', /* cHRM */ 217 104, 73, 83, 84, '\0', /* hIST */ 218 105, 67, 67, 80, '\0', /* iCCP */ 219 105, 84, 88, 116, '\0', /* iTXt */ 220 111, 70, 70, 115, '\0', /* oFFs */ 221 112, 67, 65, 76, '\0', /* pCAL */ 222 112, 72, 89, 115, '\0', /* pHYs */ 223 115, 66, 73, 84, '\0', /* sBIT */ 224 115, 67, 65, 76, '\0', /* sCAL */ 225 115, 80, 76, 84, '\0', /* sPLT */ 226 115, 84, 69, 82, '\0', /* sTER */ 227 116, 69, 88, 116, '\0', /* tEXt */ 228 116, 73, 77, 69, '\0', /* tIME */ 229 122, 84, 88, 116, '\0' /* zTXt */ 230 }; 231 232 png_set_keep_unknown_chunks(png_ptr, 1 /* PNG_HANDLE_CHUNK_NEVER */, 233 chunks_to_ignore, sizeof(chunks_to_ignore)/5); 234 } 235 #endif /* PNG_UNKNOWN_CHUNKS_SUPPORTED */ 236 237 238 /* instead of doing png_init_io() here, now we set up our callback 239 * functions for progressive decoding */ 240 241 png_set_progressive_read_fn(png_ptr, mainprog_ptr, 242 readpng2_info_callback, readpng2_row_callback, readpng2_end_callback); 243 244 245 /* 246 * may as well enable or disable MMX routines here, if supported; 247 * 248 * to enable all: mask = png_get_mmx_flagmask ( 249 * PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID); 250 * flags = png_get_asm_flags (png_ptr); 251 * flags |= mask; 252 * png_set_asm_flags (png_ptr, flags); 253 * 254 * to disable all: mask = png_get_mmx_flagmask ( 255 * PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID); 256 * flags = png_get_asm_flags (png_ptr); 257 * flags &= ~mask; 258 * png_set_asm_flags (png_ptr, flags); 259 */ 260 261 #if (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__)) && \ 262 defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200) 263 /* 264 * WARNING: This preprocessor approach means that the following code 265 * cannot be used with a libpng DLL older than 1.2.0--the 266 * compiled-in symbols for the new functions will not exist. 267 * (Could use dlopen() and dlsym() on Unix and corresponding 268 * calls for Windows, but not portable...) 269 */ 270 { 271 #ifdef PNG_ASSEMBLER_CODE_SUPPORTED 272 png_uint_32 mmx_disable_mask = 0; 273 png_uint_32 asm_flags, mmx_mask; 274 int compilerID; 275 276 if (mainprog_ptr->nommxfilters) 277 mmx_disable_mask |= ( PNG_ASM_FLAG_MMX_READ_FILTER_SUB \ 278 | PNG_ASM_FLAG_MMX_READ_FILTER_UP \ 279 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \ 280 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH ); 281 if (mainprog_ptr->nommxcombine) 282 mmx_disable_mask |= PNG_ASM_FLAG_MMX_READ_COMBINE_ROW; 283 if (mainprog_ptr->nommxinterlace) 284 mmx_disable_mask |= PNG_ASM_FLAG_MMX_READ_INTERLACE; 285 asm_flags = png_get_asm_flags(png_ptr); 286 png_set_asm_flags(png_ptr, asm_flags & ~mmx_disable_mask); 287 288 289 /* Now query libpng's asm settings, just for yuks. Note that this 290 * differs from the querying of its *potential* MMX capabilities 291 * in readpng2_version_info(); this is true runtime verification. */ 292 293 asm_flags = png_get_asm_flags(png_ptr); 294 mmx_mask = png_get_mmx_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE, 295 &compilerID); 296 if (asm_flags & PNG_ASM_FLAG_MMX_SUPPORT_COMPILED) 297 fprintf(stderr, 298 " MMX support (%s version) is compiled into libpng\n", 299 compilerID == 1? "MSVC++" : 300 (compilerID == 2? "GNU C" : "unknown")); 301 else 302 fprintf(stderr, " MMX support is not compiled into libpng\n"); 303 fprintf(stderr, " MMX instructions are %ssupported by CPU\n", 304 (asm_flags & PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU)? "" : "not "); 305 fprintf(stderr, " MMX read support for combining rows is %sabled\n", 306 (asm_flags & PNG_ASM_FLAG_MMX_READ_COMBINE_ROW)? "en" : "dis"); 307 fprintf(stderr, 308 " MMX read support for expanding interlacing is %sabled\n", 309 (asm_flags & PNG_ASM_FLAG_MMX_READ_INTERLACE)? "en" : "dis"); 310 fprintf(stderr, " MMX read support for \"sub\" filter is %sabled\n", 311 (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_SUB)? "en" : "dis"); 312 fprintf(stderr, " MMX read support for \"up\" filter is %sabled\n", 313 (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_UP)? "en" : "dis"); 314 fprintf(stderr, " MMX read support for \"avg\" filter is %sabled\n", 315 (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_AVG)? "en" : "dis"); 316 fprintf(stderr, " MMX read support for \"Paeth\" filter is %sabled\n", 317 (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_PAETH)? "en" : "dis"); 318 asm_flags &= (mmx_mask & ~( PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \ 319 | PNG_ASM_FLAG_MMX_READ_INTERLACE \ 320 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \ 321 | PNG_ASM_FLAG_MMX_READ_FILTER_UP \ 322 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \ 323 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH )); 324 if (asm_flags) 325 fprintf(stderr, 326 " additional MMX support is also enabled (0x%02lx)\n", 327 asm_flags); 328 #else /* !PNG_ASSEMBLER_CODE_SUPPORTED */ 329 fprintf(stderr, " MMX querying is disabled in libpng.\n"); 330 #endif /* ?PNG_ASSEMBLER_CODE_SUPPORTED */ 331 } 332 #endif 333 334 335 /* make sure we save our pointers for use in readpng2_decode_data() */ 336 337 mainprog_ptr->png_ptr = png_ptr; 338 mainprog_ptr->info_ptr = info_ptr; 339 340 341 /* and that's all there is to initialization */ 342 343 return 0; 344 } 345 346 347 348 349 /* returns 0 for success, 2 for libpng (longjmp) problem */ 350 351 int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length) 352 { 353 png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr; 354 png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr; 355 356 357 /* setjmp() must be called in every function that calls a PNG-reading 358 * libpng function */ 359 360 if (setjmp(mainprog_ptr->jmpbuf)) { 361 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 362 mainprog_ptr->png_ptr = NULL; 363 mainprog_ptr->info_ptr = NULL; 364 return 2; 365 } 366 367 368 /* hand off the next chunk of input data to libpng for decoding */ 369 370 png_process_data(png_ptr, info_ptr, rawbuf, length); 371 372 return 0; 373 } 374 375 376 377 378 static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr) 379 { 380 mainprog_info *mainprog_ptr; 381 int color_type, bit_depth; 382 png_uint_32 width, height; 383 double gamma; 384 385 386 /* setjmp() doesn't make sense here, because we'd either have to exit(), 387 * longjmp() ourselves, or return control to libpng, which doesn't want 388 * to see us again. By not doing anything here, libpng will instead jump 389 * to readpng2_decode_data(), which can return an error value to the main 390 * program. */ 391 392 393 /* retrieve the pointer to our special-purpose struct, using the png_ptr 394 * that libpng passed back to us (i.e., not a global this time--there's 395 * no real difference for a single image, but for a multithreaded browser 396 * decoding several PNG images at the same time, one needs to avoid mixing 397 * up different images' structs) */ 398 399 mainprog_ptr = png_get_progressive_ptr(png_ptr); 400 401 if (mainprog_ptr == NULL) { /* we be hosed */ 402 fprintf(stderr, 403 "readpng2 error: main struct not recoverable in info_callback.\n"); 404 fflush(stderr); 405 return; 406 /* 407 * Alternatively, we could call our error-handler just like libpng 408 * does, which would effectively terminate the program. Since this 409 * can only happen if png_ptr gets redirected somewhere odd or the 410 * main PNG struct gets wiped, we're probably toast anyway. (If 411 * png_ptr itself is NULL, we would not have been called.) 412 */ 413 } 414 415 416 /* this is just like in the non-progressive case */ 417 418 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 419 NULL, NULL, NULL); 420 mainprog_ptr->width = (ulg)width; 421 mainprog_ptr->height = (ulg)height; 422 423 424 /* since we know we've read all of the PNG file's "header" (i.e., up 425 * to IDAT), we can check for a background color here */ 426 427 if (mainprog_ptr->need_bgcolor && 428 png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD)) 429 { 430 png_color_16p pBackground; 431 432 /* it is not obvious from the libpng documentation, but this function 433 * takes a pointer to a pointer, and it always returns valid red, 434 * green and blue values, regardless of color_type: */ 435 png_get_bKGD(png_ptr, info_ptr, &pBackground); 436 437 /* however, it always returns the raw bKGD data, regardless of any 438 * bit-depth transformations, so check depth and adjust if necessary */ 439 if (bit_depth == 16) { 440 mainprog_ptr->bg_red = pBackground->red >> 8; 441 mainprog_ptr->bg_green = pBackground->green >> 8; 442 mainprog_ptr->bg_blue = pBackground->blue >> 8; 443 } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) { 444 if (bit_depth == 1) 445 mainprog_ptr->bg_red = mainprog_ptr->bg_green = 446 mainprog_ptr->bg_blue = pBackground->gray? 255 : 0; 447 else if (bit_depth == 2) 448 mainprog_ptr->bg_red = mainprog_ptr->bg_green = 449 mainprog_ptr->bg_blue = (255/3) * pBackground->gray; 450 else /* bit_depth == 4 */ 451 mainprog_ptr->bg_red = mainprog_ptr->bg_green = 452 mainprog_ptr->bg_blue = (255/15) * pBackground->gray; 453 } else { 454 mainprog_ptr->bg_red = (uch)pBackground->red; 455 mainprog_ptr->bg_green = (uch)pBackground->green; 456 mainprog_ptr->bg_blue = (uch)pBackground->blue; 457 } 458 } 459 460 461 /* as before, let libpng expand palette images to RGB, low-bit-depth 462 * grayscale images to 8 bits, transparency chunks to full alpha channel; 463 * strip 16-bit-per-sample images to 8 bits per sample; and convert 464 * grayscale to RGB[A] */ 465 466 if (color_type == PNG_COLOR_TYPE_PALETTE) 467 png_set_expand(png_ptr); 468 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 469 png_set_expand(png_ptr); 470 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 471 png_set_expand(png_ptr); 472 if (bit_depth == 16) 473 png_set_strip_16(png_ptr); 474 if (color_type == PNG_COLOR_TYPE_GRAY || 475 color_type == PNG_COLOR_TYPE_GRAY_ALPHA) 476 png_set_gray_to_rgb(png_ptr); 477 478 479 /* Unlike the basic viewer, which was designed to operate on local files, 480 * this program is intended to simulate a web browser--even though we 481 * actually read from a local file, too. But because we are pretending 482 * that most of the images originate on the Internet, we follow the recom- 483 * mendation of the sRGB proposal and treat unlabelled images (no gAMA 484 * chunk) as existing in the sRGB color space. That is, we assume that 485 * such images have a file gamma of 0.45455, which corresponds to a PC-like 486 * display system. This change in assumptions will have no effect on a 487 * PC-like system, but on a Mac, SGI, NeXT or other system with a non- 488 * identity lookup table, it will darken unlabelled images, which effec- 489 * tively favors images from PC-like systems over those originating on 490 * the local platform. Note that mainprog_ptr->display_exponent is the 491 * "gamma" value for the entire display system, i.e., the product of 492 * LUT_exponent and CRT_exponent. */ 493 494 if (png_get_gAMA(png_ptr, info_ptr, &gamma)) 495 png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma); 496 else 497 png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455); 498 499 500 /* we'll let libpng expand interlaced images, too */ 501 502 mainprog_ptr->passes = png_set_interlace_handling(png_ptr); 503 504 505 /* all transformations have been registered; now update info_ptr data and 506 * then get rowbytes and channels */ 507 508 png_read_update_info(png_ptr, info_ptr); 509 510 mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr); 511 mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr); 512 513 514 /* Call the main program to allocate memory for the image buffer and 515 * initialize windows and whatnot. (The old-style function-pointer 516 * invocation is used for compatibility with a few supposedly ANSI 517 * compilers that nevertheless barf on "fn_ptr()"-style syntax.) */ 518 519 (*mainprog_ptr->mainprog_init)(); 520 521 522 /* and that takes care of initialization */ 523 524 return; 525 } 526 527 528 529 530 531 static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row, 532 png_uint_32 row_num, int pass) 533 { 534 mainprog_info *mainprog_ptr; 535 536 537 /* first check whether the row differs from the previous pass; if not, 538 * nothing to combine or display */ 539 540 if (!new_row) 541 return; 542 543 544 /* retrieve the pointer to our special-purpose struct so we can access 545 * the old rows and image-display callback function */ 546 547 mainprog_ptr = png_get_progressive_ptr(png_ptr); 548 549 550 /* save the pass number for optional use by the front end */ 551 552 mainprog_ptr->pass = pass; 553 554 555 /* have libpng either combine the new row data with the existing row data 556 * from previous passes (if interlaced) or else just copy the new row 557 * into the main program's image buffer */ 558 559 png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num], 560 new_row); 561 562 563 /* finally, call the display routine in the main program with the number 564 * of the row we just updated */ 565 566 (*mainprog_ptr->mainprog_display_row)(row_num); 567 568 569 /* and we're ready for more */ 570 571 return; 572 } 573 574 575 576 577 578 static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr) 579 { 580 mainprog_info *mainprog_ptr; 581 582 583 /* retrieve the pointer to our special-purpose struct */ 584 585 mainprog_ptr = png_get_progressive_ptr(png_ptr); 586 587 588 /* let the main program know that it should flush any buffered image 589 * data to the display now and set a "done" flag or whatever, but note 590 * that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do 591 * NOT call readpng2_cleanup() either here or in the finish_display() 592 * routine; wait until control returns to the main program via 593 * readpng2_decode_data() */ 594 595 (*mainprog_ptr->mainprog_finish_display)(); 596 597 598 /* all done */ 599 600 return; 601 } 602 603 604 605 606 607 void readpng2_cleanup(mainprog_info *mainprog_ptr) 608 { 609 png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr; 610 png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr; 611 612 if (png_ptr && info_ptr) 613 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 614 615 mainprog_ptr->png_ptr = NULL; 616 mainprog_ptr->info_ptr = NULL; 617 } 618 619 620 621 622 623 static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg) 624 { 625 mainprog_info *mainprog_ptr; 626 627 /* This function, aside from the extra step of retrieving the "error 628 * pointer" (below) and the fact that it exists within the application 629 * rather than within libpng, is essentially identical to libpng's 630 * default error handler. The second point is critical: since both 631 * setjmp() and longjmp() are called from the same code, they are 632 * guaranteed to have compatible notions of how big a jmp_buf is, 633 * regardless of whether _BSD_SOURCE or anything else has (or has not) 634 * been defined. */ 635 636 fprintf(stderr, "readpng2 libpng error: %s\n", msg); 637 fflush(stderr); 638 639 mainprog_ptr = png_get_error_ptr(png_ptr); 640 if (mainprog_ptr == NULL) { /* we are completely hosed now */ 641 fprintf(stderr, 642 "readpng2 severe error: jmpbuf not recoverable; terminating.\n"); 643 fflush(stderr); 644 exit(99); 645 } 646 647 longjmp(mainprog_ptr->jmpbuf, 1); 648 } 649
