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https://git.code.sf.net/p/libpng/code.git
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73e28ef13d
where it is not appropriate. If mainprog->jmpbuf is used by setjmp, then png_longjmp cannot be used. Reversed patch to remove error handler when the jmp_buf is stored in the main program structure, not the png_struct. The error handler is needed because the default handler in libpng will always use the jmp_buf in the library control structure; this is never set. The gregbook code is a useful example because, even though it uses setjmp/longjmp, it shows how error handling can be implemented using control mechanisms not directly supported by libpng. The technique will work correctly with mechanisms such as Microsoft Structure Exceptions or C++ exceptions (compiler willing - note that gcc does not by default support interworking of C and C++ error handling.)
492 lines
17 KiB
C
492 lines
17 KiB
C
/*---------------------------------------------------------------------------
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rpng2 - progressive-model PNG display program readpng2.c
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---------------------------------------------------------------------------
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Copyright (c) 1998-2007 Greg Roelofs. All rights reserved.
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This software is provided "as is," without warranty of any kind,
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express or implied. In no event shall the author or contributors
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be held liable for any damages arising in any way from the use of
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this software.
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The contents of this file are DUAL-LICENSED. You may modify and/or
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redistribute this software according to the terms of one of the
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following two licenses (at your option):
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LICENSE 1 ("BSD-like with advertising clause"):
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute
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it freely, subject to the following restrictions:
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1. Redistributions of source code must retain the above copyright
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notice, disclaimer, and this list of conditions.
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2. Redistributions in binary form must reproduce the above copyright
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notice, disclaimer, and this list of conditions in the documenta-
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tion and/or other materials provided with the distribution.
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3. All advertising materials mentioning features or use of this
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software must display the following acknowledgment:
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This product includes software developed by Greg Roelofs
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and contributors for the book, "PNG: The Definitive Guide,"
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published by O'Reilly and Associates.
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LICENSE 2 (GNU GPL v2 or later):
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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---------------------------------------------------------------------------*/
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#include <stdlib.h> /* for exit() prototype */
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#include "png.h" /* libpng header; includes zlib.h and setjmp.h */
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#include "readpng2.h" /* typedefs, common macros, public prototypes */
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/* local prototypes */
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static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr);
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static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
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png_uint_32 row_num, int pass);
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static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr);
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static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg);
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void readpng2_version_info(void)
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{
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fprintf(stderr, " Compiled with libpng %s; using libpng %s\n",
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PNG_LIBPNG_VER_STRING, png_libpng_ver);
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fprintf(stderr, " and with zlib %s; using zlib %s.\n",
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ZLIB_VERSION, zlib_version);
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}
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int readpng2_check_sig(uch *sig, int num)
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{
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return !png_sig_cmp(sig, 0, num);
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}
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/* returns 0 for success, 2 for libpng problem, 4 for out of memory */
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int readpng2_init(mainprog_info *mainprog_ptr)
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{
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png_structp png_ptr; /* note: temporary variables! */
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png_infop info_ptr;
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/* could also replace libpng warning-handler (final NULL), but no need: */
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png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
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readpng2_error_handler, NULL);
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if (!png_ptr)
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return 4; /* out of memory */
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info_ptr = png_create_info_struct(png_ptr);
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if (!info_ptr) {
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png_destroy_read_struct(&png_ptr, NULL, NULL);
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return 4; /* out of memory */
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}
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/* we could create a second info struct here (end_info), but it's only
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* useful if we want to keep pre- and post-IDAT chunk info separated
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* (mainly for PNG-aware image editors and converters) */
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/* setjmp() must be called in every function that calls a PNG-reading
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* libpng function, unless an alternate error handler was installed--
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* but compatible error handlers must either use longjmp() themselves
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* (as in this program) or exit immediately, so here we are: */
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if (setjmp(mainprog_ptr->jmpbuf)) {
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png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
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return 2;
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}
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#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
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/* prepare the reader to ignore all recognized chunks whose data won't be
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* used, i.e., all chunks recognized by libpng except for IHDR, PLTE, IDAT,
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* IEND, tRNS, bKGD, gAMA, and sRGB (small performance improvement) */
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{
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/* These byte strings were copied from png.h. If a future libpng
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* version recognizes more chunks, add them to this list. If a
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* future version of readpng2.c recognizes more chunks, delete them
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* from this list. */
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static const png_byte chunks_to_ignore[] = {
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99, 72, 82, 77, '\0', /* cHRM */
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104, 73, 83, 84, '\0', /* hIST */
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105, 67, 67, 80, '\0', /* iCCP */
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105, 84, 88, 116, '\0', /* iTXt */
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111, 70, 70, 115, '\0', /* oFFs */
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112, 67, 65, 76, '\0', /* pCAL */
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112, 72, 89, 115, '\0', /* pHYs */
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115, 66, 73, 84, '\0', /* sBIT */
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115, 67, 65, 76, '\0', /* sCAL */
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115, 80, 76, 84, '\0', /* sPLT */
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115, 84, 69, 82, '\0', /* sTER */
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116, 69, 88, 116, '\0', /* tEXt */
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116, 73, 77, 69, '\0', /* tIME */
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122, 84, 88, 116, '\0' /* zTXt */
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};
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png_set_keep_unknown_chunks(png_ptr, 1 /* PNG_HANDLE_CHUNK_NEVER */,
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chunks_to_ignore, sizeof(chunks_to_ignore)/5);
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}
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#endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */
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/* instead of doing png_init_io() here, now we set up our callback
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* functions for progressive decoding */
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png_set_progressive_read_fn(png_ptr, mainprog_ptr,
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readpng2_info_callback, readpng2_row_callback, readpng2_end_callback);
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/* make sure we save our pointers for use in readpng2_decode_data() */
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mainprog_ptr->png_ptr = png_ptr;
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mainprog_ptr->info_ptr = info_ptr;
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/* and that's all there is to initialization */
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return 0;
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}
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/* returns 0 for success, 2 for libpng (longjmp) problem */
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int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length)
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{
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png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
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png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
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/* setjmp() must be called in every function that calls a PNG-reading
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* libpng function */
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if (setjmp(mainprog_ptr->jmpbuf)) {
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png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
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mainprog_ptr->png_ptr = NULL;
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mainprog_ptr->info_ptr = NULL;
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return 2;
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}
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/* hand off the next chunk of input data to libpng for decoding */
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png_process_data(png_ptr, info_ptr, rawbuf, length);
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return 0;
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}
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static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr)
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{
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mainprog_info *mainprog_ptr;
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int color_type, bit_depth;
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png_uint_32 width, height;
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double gamma;
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/* setjmp() doesn't make sense here, because we'd either have to exit(),
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* longjmp() ourselves, or return control to libpng, which doesn't want
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* to see us again. By not doing anything here, libpng will instead jump
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* to readpng2_decode_data(), which can return an error value to the main
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* program. */
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/* retrieve the pointer to our special-purpose struct, using the png_ptr
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* that libpng passed back to us (i.e., not a global this time--there's
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* no real difference for a single image, but for a multithreaded browser
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* decoding several PNG images at the same time, one needs to avoid mixing
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* up different images' structs) */
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mainprog_ptr = png_get_progressive_ptr(png_ptr);
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if (mainprog_ptr == NULL) { /* we be hosed */
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fprintf(stderr,
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"readpng2 error: main struct not recoverable in info_callback.\n");
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fflush(stderr);
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return;
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/*
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* Alternatively, we could call our error-handler just like libpng
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* does, which would effectively terminate the program. Since this
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* can only happen if png_ptr gets redirected somewhere odd or the
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* main PNG struct gets wiped, we're probably toast anyway. (If
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* png_ptr itself is NULL, we would not have been called.)
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*/
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}
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/* this is just like in the non-progressive case */
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png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
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NULL, NULL, NULL);
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mainprog_ptr->width = (ulg)width;
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mainprog_ptr->height = (ulg)height;
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/* since we know we've read all of the PNG file's "header" (i.e., up
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* to IDAT), we can check for a background color here */
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if (mainprog_ptr->need_bgcolor &&
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png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
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{
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png_color_16p pBackground;
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/* it is not obvious from the libpng documentation, but this function
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* takes a pointer to a pointer, and it always returns valid red,
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* green and blue values, regardless of color_type: */
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png_get_bKGD(png_ptr, info_ptr, &pBackground);
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/* however, it always returns the raw bKGD data, regardless of any
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* bit-depth transformations, so check depth and adjust if necessary */
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if (bit_depth == 16) {
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mainprog_ptr->bg_red = pBackground->red >> 8;
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mainprog_ptr->bg_green = pBackground->green >> 8;
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mainprog_ptr->bg_blue = pBackground->blue >> 8;
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} else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
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if (bit_depth == 1)
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mainprog_ptr->bg_red = mainprog_ptr->bg_green =
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mainprog_ptr->bg_blue = pBackground->gray? 255 : 0;
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else if (bit_depth == 2)
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mainprog_ptr->bg_red = mainprog_ptr->bg_green =
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mainprog_ptr->bg_blue = (255/3) * pBackground->gray;
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else /* bit_depth == 4 */
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mainprog_ptr->bg_red = mainprog_ptr->bg_green =
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mainprog_ptr->bg_blue = (255/15) * pBackground->gray;
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} else {
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mainprog_ptr->bg_red = (uch)pBackground->red;
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mainprog_ptr->bg_green = (uch)pBackground->green;
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mainprog_ptr->bg_blue = (uch)pBackground->blue;
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}
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}
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/* as before, let libpng expand palette images to RGB, low-bit-depth
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* grayscale images to 8 bits, transparency chunks to full alpha channel;
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* strip 16-bit-per-sample images to 8 bits per sample; and convert
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* grayscale to RGB[A] */
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if (color_type == PNG_COLOR_TYPE_PALETTE)
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png_set_expand(png_ptr);
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if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
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png_set_expand(png_ptr);
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if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
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png_set_expand(png_ptr);
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if (bit_depth == 16)
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png_set_strip_16(png_ptr);
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if (color_type == PNG_COLOR_TYPE_GRAY ||
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color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
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png_set_gray_to_rgb(png_ptr);
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/* Unlike the basic viewer, which was designed to operate on local files,
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* this program is intended to simulate a web browser--even though we
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* actually read from a local file, too. But because we are pretending
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* that most of the images originate on the Internet, we follow the recom-
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* mendation of the sRGB proposal and treat unlabelled images (no gAMA
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* chunk) as existing in the sRGB color space. That is, we assume that
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* such images have a file gamma of 0.45455, which corresponds to a PC-like
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* display system. This change in assumptions will have no effect on a
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* PC-like system, but on a Mac, SGI, NeXT or other system with a non-
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* identity lookup table, it will darken unlabelled images, which effec-
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* tively favors images from PC-like systems over those originating on
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* the local platform. Note that mainprog_ptr->display_exponent is the
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* "gamma" value for the entire display system, i.e., the product of
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* LUT_exponent and CRT_exponent. */
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if (png_get_gAMA(png_ptr, info_ptr, &gamma))
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png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma);
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else
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png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455);
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/* we'll let libpng expand interlaced images, too */
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mainprog_ptr->passes = png_set_interlace_handling(png_ptr);
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/* all transformations have been registered; now update info_ptr data and
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* then get rowbytes and channels */
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png_read_update_info(png_ptr, info_ptr);
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mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr);
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mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr);
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/* Call the main program to allocate memory for the image buffer and
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* initialize windows and whatnot. (The old-style function-pointer
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* invocation is used for compatibility with a few supposedly ANSI
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* compilers that nevertheless barf on "fn_ptr()"-style syntax.) */
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(*mainprog_ptr->mainprog_init)();
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/* and that takes care of initialization */
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return;
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}
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static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
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png_uint_32 row_num, int pass)
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{
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mainprog_info *mainprog_ptr;
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/* first check whether the row differs from the previous pass; if not,
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* nothing to combine or display */
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if (!new_row)
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return;
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/* retrieve the pointer to our special-purpose struct so we can access
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* the old rows and image-display callback function */
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mainprog_ptr = png_get_progressive_ptr(png_ptr);
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/* save the pass number for optional use by the front end */
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mainprog_ptr->pass = pass;
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/* have libpng either combine the new row data with the existing row data
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* from previous passes (if interlaced) or else just copy the new row
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* into the main program's image buffer */
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png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num],
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new_row);
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/* finally, call the display routine in the main program with the number
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* of the row we just updated */
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(*mainprog_ptr->mainprog_display_row)(row_num);
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/* and we're ready for more */
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return;
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}
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static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr)
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{
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mainprog_info *mainprog_ptr;
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/* retrieve the pointer to our special-purpose struct */
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mainprog_ptr = png_get_progressive_ptr(png_ptr);
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/* let the main program know that it should flush any buffered image
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* data to the display now and set a "done" flag or whatever, but note
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* that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do
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* NOT call readpng2_cleanup() either here or in the finish_display()
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* routine; wait until control returns to the main program via
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* readpng2_decode_data() */
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(*mainprog_ptr->mainprog_finish_display)();
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/* all done */
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return;
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}
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void readpng2_cleanup(mainprog_info *mainprog_ptr)
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{
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png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
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png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
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if (png_ptr && info_ptr)
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png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
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mainprog_ptr->png_ptr = NULL;
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mainprog_ptr->info_ptr = NULL;
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}
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static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg)
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{
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mainprog_info *mainprog_ptr;
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/* This function, aside from the extra step of retrieving the "error
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* pointer" (below) and the fact that it exists within the application
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* rather than within libpng, is essentially identical to libpng's
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* default error handler. The second point is critical: since both
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* setjmp() and longjmp() are called from the same code, they are
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* guaranteed to have compatible notions of how big a jmp_buf is,
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* regardless of whether _BSD_SOURCE or anything else has (or has not)
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* been defined. */
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fprintf(stderr, "readpng2 libpng error: %s\n", msg);
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fflush(stderr);
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mainprog_ptr = png_get_error_ptr(png_ptr);
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if (mainprog_ptr == NULL) { /* we are completely hosed now */
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fprintf(stderr,
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"readpng2 severe error: jmpbuf not recoverable; terminating.\n");
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fflush(stderr);
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exit(99);
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}
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/* Now we have our data structure we can use the information in it
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* to return control to our own higher level code (all the points
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* where 'setjmp' is called in this file.) This will work with other
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* error handling mechanisms as well - libpng always calls png_error
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* when it can proceed no further, thus, so long as the error handler
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* is intercepted, application code can do its own error recovery.
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*/
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longjmp(mainprog_ptr->jmpbuf, 1);
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}
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