1 /*---------------------------------------------------------------------------
3 rpng2 - progressive-model PNG display program readpng2.c
5 ---------------------------------------------------------------------------
7 Copyright (c) 1998-2007 Greg Roelofs. All rights reserved.
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
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):
19 LICENSE 1 ("BSD-like with advertising clause"):
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:
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:
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.
38 LICENSE 2 (GNU GPL v2 or later):
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.
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.
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
54 ---------------------------------------------------------------------------*/
57 #include <stdlib.h> /* for exit() prototype */
61 #include "png.h" /* libpng header from the local directory */
62 #include "readpng2.h" /* typedefs, common macros, public prototypes */
65 /* local prototypes */
67 static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr);
68 static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
69 png_uint_32 row_num, int pass);
70 static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr);
71 static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg);
76 void readpng2_version_info(void)
78 fprintf(stderr, " Compiled with libpng %s; using libpng %s\n",
79 PNG_LIBPNG_VER_STRING, png_libpng_ver);
81 fprintf(stderr, " and with zlib %s; using zlib %s.\n",
82 ZLIB_VERSION, zlib_version);
88 int readpng2_check_sig(uch *sig, int num)
90 return !png_sig_cmp(sig, 0, num);
96 /* returns 0 for success, 2 for libpng problem, 4 for out of memory */
98 int readpng2_init(mainprog_info *mainprog_ptr)
100 png_structp png_ptr; /* note: temporary variables! */
104 /* could also replace libpng warning-handler (final NULL), but no need: */
106 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
107 readpng2_error_handler, NULL);
109 return 4; /* out of memory */
111 info_ptr = png_create_info_struct(png_ptr);
113 png_destroy_read_struct(&png_ptr, NULL, NULL);
114 return 4; /* out of memory */
118 /* we could create a second info struct here (end_info), but it's only
119 * useful if we want to keep pre- and post-IDAT chunk info separated
120 * (mainly for PNG-aware image editors and converters) */
123 /* setjmp() must be called in every function that calls a PNG-reading
124 * libpng function, unless an alternate error handler was installed--
125 * but compatible error handlers must either use longjmp() themselves
126 * (as in this program) or exit immediately, so here we are: */
128 if (setjmp(mainprog_ptr->jmpbuf)) {
129 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
134 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
135 /* prepare the reader to ignore all recognized chunks whose data won't be
136 * used, i.e., all chunks recognized by libpng except for IHDR, PLTE, IDAT,
137 * IEND, tRNS, bKGD, gAMA, and sRGB (small performance improvement) */
139 /* These byte strings were copied from png.h. If a future version
140 * of readpng2.c recognizes more chunks, add them to this list.
142 static PNG_CONST png_byte chunks_to_process[] = {
143 98, 75, 71, 68, '\0', /* bKGD */
144 103, 65, 77, 65, '\0', /* gAMA */
145 115, 82, 71, 66, '\0', /* sRGB */
148 /* Ignore all chunks except for IHDR, PLTE, tRNS, IDAT, and IEND */
149 png_set_keep_unknown_chunks(png_ptr, -1 /* PNG_HANDLE_CHUNK_NEVER */,
152 /* But do not ignore chunks in the "chunks_to_process" list */
153 png_set_keep_unknown_chunks(png_ptr,
154 0 /* PNG_HANDLE_CHUNK_AS_DEFAULT */, chunks_to_process,
155 sizeof(chunks_to_process)/5);
157 #endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */
160 /* instead of doing png_init_io() here, now we set up our callback
161 * functions for progressive decoding */
163 png_set_progressive_read_fn(png_ptr, mainprog_ptr,
164 readpng2_info_callback, readpng2_row_callback, readpng2_end_callback);
167 /* make sure we save our pointers for use in readpng2_decode_data() */
169 mainprog_ptr->png_ptr = png_ptr;
170 mainprog_ptr->info_ptr = info_ptr;
173 /* and that's all there is to initialization */
181 /* returns 0 for success, 2 for libpng (longjmp) problem */
183 int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length)
185 png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
186 png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
189 /* setjmp() must be called in every function that calls a PNG-reading
192 if (setjmp(mainprog_ptr->jmpbuf)) {
193 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
194 mainprog_ptr->png_ptr = NULL;
195 mainprog_ptr->info_ptr = NULL;
200 /* hand off the next chunk of input data to libpng for decoding */
202 png_process_data(png_ptr, info_ptr, rawbuf, length);
210 static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr)
212 mainprog_info *mainprog_ptr;
213 int color_type, bit_depth;
214 png_uint_32 width, height;
215 #ifdef PNG_FLOATING_POINT_SUPPORTED
218 png_fixed_point gamma;
222 /* setjmp() doesn't make sense here, because we'd either have to exit(),
223 * longjmp() ourselves, or return control to libpng, which doesn't want
224 * to see us again. By not doing anything here, libpng will instead jump
225 * to readpng2_decode_data(), which can return an error value to the main
229 /* retrieve the pointer to our special-purpose struct, using the png_ptr
230 * that libpng passed back to us (i.e., not a global this time--there's
231 * no real difference for a single image, but for a multithreaded browser
232 * decoding several PNG images at the same time, one needs to avoid mixing
233 * up different images' structs) */
235 mainprog_ptr = png_get_progressive_ptr(png_ptr);
237 if (mainprog_ptr == NULL) { /* we be hosed */
239 "readpng2 error: main struct not recoverable in info_callback.\n");
243 * Alternatively, we could call our error-handler just like libpng
244 * does, which would effectively terminate the program. Since this
245 * can only happen if png_ptr gets redirected somewhere odd or the
246 * main PNG struct gets wiped, we're probably toast anyway. (If
247 * png_ptr itself is NULL, we would not have been called.)
252 /* this is just like in the non-progressive case */
254 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
256 mainprog_ptr->width = (ulg)width;
257 mainprog_ptr->height = (ulg)height;
260 /* since we know we've read all of the PNG file's "header" (i.e., up
261 * to IDAT), we can check for a background color here */
263 if (mainprog_ptr->need_bgcolor &&
264 png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
266 png_color_16p pBackground;
268 /* it is not obvious from the libpng documentation, but this function
269 * takes a pointer to a pointer, and it always returns valid red,
270 * green and blue values, regardless of color_type: */
271 png_get_bKGD(png_ptr, info_ptr, &pBackground);
273 /* however, it always returns the raw bKGD data, regardless of any
274 * bit-depth transformations, so check depth and adjust if necessary */
275 if (bit_depth == 16) {
276 mainprog_ptr->bg_red = pBackground->red >> 8;
277 mainprog_ptr->bg_green = pBackground->green >> 8;
278 mainprog_ptr->bg_blue = pBackground->blue >> 8;
279 } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
281 mainprog_ptr->bg_red = mainprog_ptr->bg_green =
282 mainprog_ptr->bg_blue = pBackground->gray? 255 : 0;
283 else if (bit_depth == 2)
284 mainprog_ptr->bg_red = mainprog_ptr->bg_green =
285 mainprog_ptr->bg_blue = (255/3) * pBackground->gray;
286 else /* bit_depth == 4 */
287 mainprog_ptr->bg_red = mainprog_ptr->bg_green =
288 mainprog_ptr->bg_blue = (255/15) * pBackground->gray;
290 mainprog_ptr->bg_red = (uch)pBackground->red;
291 mainprog_ptr->bg_green = (uch)pBackground->green;
292 mainprog_ptr->bg_blue = (uch)pBackground->blue;
297 /* as before, let libpng expand palette images to RGB, low-bit-depth
298 * grayscale images to 8 bits, transparency chunks to full alpha channel;
299 * strip 16-bit-per-sample images to 8 bits per sample; and convert
300 * grayscale to RGB[A] */
302 if (color_type == PNG_COLOR_TYPE_PALETTE)
303 png_set_expand(png_ptr);
304 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
305 png_set_expand(png_ptr);
306 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
307 png_set_expand(png_ptr);
308 #ifdef PNG_READ_16_TO_8_SUPPORTED
310 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
311 png_set_scale_16(png_ptr);
313 png_set_strip_16(png_ptr);
316 if (color_type == PNG_COLOR_TYPE_GRAY ||
317 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
318 png_set_gray_to_rgb(png_ptr);
321 /* Unlike the basic viewer, which was designed to operate on local files,
322 * this program is intended to simulate a web browser--even though we
323 * actually read from a local file, too. But because we are pretending
324 * that most of the images originate on the Internet, we follow the recom-
325 * mendation of the sRGB proposal and treat unlabelled images (no gAMA
326 * chunk) as existing in the sRGB color space. That is, we assume that
327 * such images have a file gamma of 0.45455, which corresponds to a PC-like
328 * display system. This change in assumptions will have no effect on a
329 * PC-like system, but on a Mac, SGI, NeXT or other system with a non-
330 * identity lookup table, it will darken unlabelled images, which effec-
331 * tively favors images from PC-like systems over those originating on
332 * the local platform. Note that mainprog_ptr->display_exponent is the
333 * "gamma" value for the entire display system, i.e., the product of
334 * LUT_exponent and CRT_exponent. */
336 #ifdef PNG_FLOATING_POINT_SUPPORTED
337 if (png_get_gAMA(png_ptr, info_ptr, &gamma))
338 png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma);
340 png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455);
342 if (png_get_gAMA_fixed(png_ptr, info_ptr, &gamma))
343 png_set_gamma_fixed(png_ptr,
344 (png_fixed_point)(100000*mainprog_ptr->display_exponent+.5), gamma);
346 png_set_gamma_fixed(png_ptr,
347 (png_fixed_point)(100000*mainprog_ptr->display_exponent+.5), 45455);
350 /* we'll let libpng expand interlaced images, too */
352 mainprog_ptr->passes = png_set_interlace_handling(png_ptr);
355 /* all transformations have been registered; now update info_ptr data and
356 * then get rowbytes and channels */
358 png_read_update_info(png_ptr, info_ptr);
360 mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr);
361 mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr);
364 /* Call the main program to allocate memory for the image buffer and
365 * initialize windows and whatnot. (The old-style function-pointer
366 * invocation is used for compatibility with a few supposedly ANSI
367 * compilers that nevertheless barf on "fn_ptr()"-style syntax.) */
369 (*mainprog_ptr->mainprog_init)();
372 /* and that takes care of initialization */
381 static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
382 png_uint_32 row_num, int pass)
384 mainprog_info *mainprog_ptr;
387 /* first check whether the row differs from the previous pass; if not,
388 * nothing to combine or display */
394 /* retrieve the pointer to our special-purpose struct so we can access
395 * the old rows and image-display callback function */
397 mainprog_ptr = png_get_progressive_ptr(png_ptr);
400 /* save the pass number for optional use by the front end */
402 mainprog_ptr->pass = pass;
405 /* have libpng either combine the new row data with the existing row data
406 * from previous passes (if interlaced) or else just copy the new row
407 * into the main program's image buffer */
409 png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num],
413 /* finally, call the display routine in the main program with the number
414 * of the row we just updated */
416 (*mainprog_ptr->mainprog_display_row)(row_num);
419 /* and we're ready for more */
428 static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr)
430 mainprog_info *mainprog_ptr;
433 /* retrieve the pointer to our special-purpose struct */
435 mainprog_ptr = png_get_progressive_ptr(png_ptr);
438 /* let the main program know that it should flush any buffered image
439 * data to the display now and set a "done" flag or whatever, but note
440 * that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do
441 * NOT call readpng2_cleanup() either here or in the finish_display()
442 * routine; wait until control returns to the main program via
443 * readpng2_decode_data() */
445 (*mainprog_ptr->mainprog_finish_display)();
457 void readpng2_cleanup(mainprog_info *mainprog_ptr)
459 png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
460 png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
462 if (png_ptr && info_ptr)
463 png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
465 mainprog_ptr->png_ptr = NULL;
466 mainprog_ptr->info_ptr = NULL;
473 static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg)
475 mainprog_info *mainprog_ptr;
477 /* This function, aside from the extra step of retrieving the "error
478 * pointer" (below) and the fact that it exists within the application
479 * rather than within libpng, is essentially identical to libpng's
480 * default error handler. The second point is critical: since both
481 * setjmp() and longjmp() are called from the same code, they are
482 * guaranteed to have compatible notions of how big a jmp_buf is,
483 * regardless of whether _BSD_SOURCE or anything else has (or has not)
486 fprintf(stderr, "readpng2 libpng error: %s\n", msg);
489 mainprog_ptr = png_get_error_ptr(png_ptr);
490 if (mainprog_ptr == NULL) { /* we are completely hosed now */
492 "readpng2 severe error: jmpbuf not recoverable; terminating.\n");
497 /* Now we have our data structure we can use the information in it
498 * to return control to our own higher level code (all the points
499 * where 'setjmp' is called in this file.) This will work with other
500 * error handling mechanisms as well - libpng always calls png_error
501 * when it can proceed no further, thus, so long as the error handler
502 * is intercepted, application code can do its own error recovery.
504 longjmp(mainprog_ptr->jmpbuf, 1);