0 +l=J 7@p/F d.>_I|+? #if 0 /* in case someone actually tries to compile this */ /* example.c - an example of using libpng * Last changed in libpng 1.5.10 [March 8, 2012] * Maintained 1998-2012 Glenn Randers-Pehrson * Maintained 1996, 1997 Andreas Dilger * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc. */ /* This is an example of how to use libpng to read and write PNG files. * The file libpng-manual.txt is much more verbose then this. If you have not * read it, do so first. This was designed to be a starting point of an * implementation. This is not officially part of libpng, is hereby placed * in the public domain, and therefore does not require a copyright notice. * To the extent possible under law, the authors have waived all copyright and * related or neighboring rights to this file. * * This file does not currently compile, because it is missing certain * parts, like allocating memory to hold an image. You will have to * supply these parts to get it to compile. For an example of a minimal * working PNG reader/writer, see pngtest.c, included in this distribution; * see also the programs in the contrib directory. */ #define _POSIX_SOURCE 1 /* libpng and zlib are POSIX-compliant. You may * change this if your application uses non-POSIX * extensions. */ #include "png.h" /* The png_jmpbuf() macro, used in error handling, became available in * libpng version 1.0.6. If you want to be able to run your code with older * versions of libpng, you must define the macro yourself (but only if it * is not already defined by libpng!). */ #ifndef png_jmpbuf # define png_jmpbuf(png_ptr) ((png_ptr)->png_jmpbuf) #endif /* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp() * returns zero if the image is a PNG and nonzero if it isn't a PNG. * * The function check_if_png() shown here, but not used, returns nonzero (true) * if the file can be opened and is a PNG, 0 (false) otherwise. * * If this call is successful, and you are going to keep the file open, * you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once * you have created the png_ptr, so that libpng knows your application * has read that many bytes from the start of the file. Make sure you * don't call png_set_sig_bytes() with more than 8 bytes read or give it * an incorrect number of bytes read, or you will either have read too * many bytes (your fault), or you are telling libpng to read the wrong * number of magic bytes (also your fault). * * Many applications already read the first 2 or 4 bytes from the start * of the image to determine the file type, so it would be easiest just * to pass the bytes to png_sig_cmp() or even skip that if you know * you have a PNG file, and call png_set_sig_bytes(). */ #define PNG_BYTES_TO_CHECK 4 int check_if_png(char *file_name, FILE **fp) { char buf[PNG_BYTES_TO_CHECK]; /* Open the prospective PNG file. */ if ((*fp = fopen(file_name, "rb")) == NULL) return 0; /* Read in some of the signature bytes */ if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK) return 0; /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature. Return nonzero (true) if they match */ return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK)); } /* Read a PNG file. You may want to return an error code if the read * fails (depending upon the failure). There are two "prototypes" given * here - one where we are given the filename, and we need to open the * file, and the other where we are given an open file (possibly with * some or all of the magic bytes read - see comments above). */ #ifdef open_file /* prototype 1 */ void read_png(char *file_name) /* We need to open the file */ { png_structp png_ptr; png_infop info_ptr; unsigned int sig_read = 0; png_uint_32 width, height; int bit_depth, color_type, interlace_type; FILE *fp; if ((fp = fopen(file_name, "rb")) == NULL) return (ERRO