1 /*--------------------------------------------------------------------------- 2 3 rpng - simple PNG display program readpng.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 #include <stdio.h> 57 #include <stdlib.h> 58 59 #include "png.h" /* libpng header; includes zlib.h */ 60 #include "readpng.h" /* typedefs, common macros, public prototypes */ 61 62 /* future versions of libpng will provide this macro: */ 63 #ifndef png_jmpbuf 64 # define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf) 65 #endif 66 67 68 static png_structp png_ptr = NULL; 69 static png_infop info_ptr = NULL; 70 71 png_uint_32 width, height; 72 int bit_depth, color_type; 73 uch *image_data = NULL; 74 75 76 void readpng_version_info(void) 77 { 78 fprintf(stderr, " Compiled with libpng %s; using libpng %s.\n", 79 PNG_LIBPNG_VER_STRING, png_libpng_ver); 80 fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n", 81 ZLIB_VERSION, zlib_version); 82 } 83 84 85 /* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */ 86 87 int readpng_init(FILE *infile, ulg *pWidth, ulg *pHeight) 88 { 89 uch sig[8]; 90 91 92 /* first do a quick check that the file really is a PNG image; could 93 * have used slightly more general png_sig_cmp() function instead */ 94 95 fread(sig, 1, 8, infile); 96 if (png_sig_cmp(sig, 0, 8)) 97 return 1; /* bad signature */ 98 99 100 /* could pass pointers to user-defined error handlers instead of NULLs: */ 101 102 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); 103 if (!png_ptr) 104 return 4; /* out of memory */ 105 106 info_ptr = png_create_info_struct(png_ptr); 107 if (!info_ptr) { 108 png_destroy_read_struct(&png_ptr, NULL, NULL); 109 return 4; /* out of memory */ 110 } 111 112 113 /* we could create a second info struct here (end_info), but it's only 114 * useful if we want to keep pre- and post-IDAT chunk info separated 115 * (mainly for PNG-aware image editors and converters) */ 116 117 118 /* setjmp() must be called in every function that calls a PNG-reading 119 * libpng function */ 120 121 if (setjmp(png_jmpbuf(png_ptr))) { 122 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 123 return 2; 124 } 125 126 127 png_init_io(png_ptr, infile); 128 png_set_sig_bytes(png_ptr, 8); /* we already read the 8 signature bytes */ 129 130 png_read_info(png_ptr, info_ptr); /* read all PNG info up to image data */ 131 132 133 /* alternatively, could make separate calls to png_get_image_width(), 134 * etc., but want bit_depth and color_type for later [don't care about 135 * compression_type and filter_type => NULLs] */ 136 137 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 138 NULL, NULL, NULL); 139 *pWidth = width; 140 *pHeight = height; 141 142 143 /* OK, that's all we need for now; return happy */ 144 145 return 0; 146 } 147 148 149 150 151 /* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error; 152 * scales values to 8-bit if necessary */ 153 154 int readpng_get_bgcolor(uch *red, uch *green, uch *blue) 155 { 156 png_color_16p pBackground; 157 158 159 /* setjmp() must be called in every function that calls a PNG-reading 160 * libpng function */ 161 162 if (setjmp(png_jmpbuf(png_ptr))) { 163 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 164 return 2; 165 } 166 167 168 if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD)) 169 return 1; 170 171 /* it is not obvious from the libpng documentation, but this function 172 * takes a pointer to a pointer, and it always returns valid red, green 173 * and blue values, regardless of color_type: */ 174 175 png_get_bKGD(png_ptr, info_ptr, &pBackground); 176 177 178 /* however, it always returns the raw bKGD data, regardless of any 179 * bit-depth transformations, so check depth and adjust if necessary */ 180 181 if (bit_depth == 16) { 182 *red = pBackground->red >> 8; 183 *green = pBackground->green >> 8; 184 *blue = pBackground->blue >> 8; 185 } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) { 186 if (bit_depth == 1) 187 *red = *green = *blue = pBackground->gray? 255 : 0; 188 else if (bit_depth == 2) 189 *red = *green = *blue = (255/3) * pBackground->gray; 190 else /* bit_depth == 4 */ 191 *red = *green = *blue = (255/15) * pBackground->gray; 192 } else { 193 *red = (uch)pBackground->red; 194 *green = (uch)pBackground->green; 195 *blue = (uch)pBackground->blue; 196 } 197 198 return 0; 199 } 200 201 202 203 204 /* display_exponent == LUT_exponent * CRT_exponent */ 205 206 uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes) 207 { 208 double gamma; 209 png_uint_32 i, rowbytes; 210 png_bytepp row_pointers = NULL; 211 212 213 /* setjmp() must be called in every function that calls a PNG-reading 214 * libpng function */ 215 216 if (setjmp(png_jmpbuf(png_ptr))) { 217 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 218 return NULL; 219 } 220 221 222 /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits, 223 * transparency chunks to full alpha channel; strip 16-bit-per-sample 224 * images to 8 bits per sample; and convert grayscale to RGB[A] */ 225 226 if (color_type == PNG_COLOR_TYPE_PALETTE) 227 png_set_expand(png_ptr); 228 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 229 png_set_expand(png_ptr); 230 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 231 png_set_expand(png_ptr); 232 if (bit_depth == 16) 233 png_set_strip_16(png_ptr); 234 if (color_type == PNG_COLOR_TYPE_GRAY || 235 color_type == PNG_COLOR_TYPE_GRAY_ALPHA) 236 png_set_gray_to_rgb(png_ptr); 237 238 239 /* unlike the example in the libpng documentation, we have *no* idea where 240 * this file may have come from--so if it doesn't have a file gamma, don't 241 * do any correction ("do no harm") */ 242 243 if (png_get_gAMA(png_ptr, info_ptr, &gamma)) 244 png_set_gamma(png_ptr, display_exponent, gamma); 245 246 247 /* all transformations have been registered; now update info_ptr data, 248 * get rowbytes and channels, and allocate image memory */ 249 250 png_read_update_info(png_ptr, info_ptr); 251 252 *pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr); 253 *pChannels = (int)png_get_channels(png_ptr, info_ptr); 254 255 if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) { 256 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 257 return NULL; 258 } 259 if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) { 260 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 261 free(image_data); 262 image_data = NULL; 263 return NULL; 264 } 265 266 Trace((stderr, "readpng_get_image: channels = %d, rowbytes = %ld, height = %ld\n", *pChannels, rowbytes, height)); 267 268 269 /* set the individual row_pointers to point at the correct offsets */ 270 271 for (i = 0; i < height; ++i) 272 row_pointers[i] = image_data + i*rowbytes; 273 274 275 /* now we can go ahead and just read the whole image */ 276 277 png_read_image(png_ptr, row_pointers); 278 279 280 /* and we're done! (png_read_end() can be omitted if no processing of 281 * post-IDAT text/time/etc. is desired) */ 282 283 free(row_pointers); 284 row_pointers = NULL; 285 286 png_read_end(png_ptr, NULL); 287 288 return image_data; 289 } 290 291 292 void readpng_cleanup(int free_image_data) 293 { 294 if (free_image_data && image_data) { 295 free(image_data); 296 image_data = NULL; 297 } 298 299 if (png_ptr && info_ptr) { 300 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 301 png_ptr = NULL; 302 info_ptr = NULL; 303 } 304 } 305
