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 #include <zlib.h> 59 60 #include "png.h" /* libpng header */ 61 #include "readpng.h" /* typedefs, common macros, public prototypes */ 62 63 /* future versions of libpng will provide this macro: */ 64 #ifndef png_jmpbuf 65 # define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf) 66 #endif 67 68 69 static png_structp png_ptr = NULL; 70 static png_infop info_ptr = NULL; 71 72 png_uint_32 width, height; 73 int bit_depth, color_type; 74 uch *image_data = NULL; 75 76 77 void readpng_version_info(void) 78 { 79 fprintf(stderr, " Compiled with libpng %s; using libpng %s.\n", 80 PNG_LIBPNG_VER_STRING, png_libpng_ver); 81 fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n", 82 ZLIB_VERSION, zlib_version); 83 } 84 85 86 /* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */ 87 88 int readpng_init(FILE *infile, ulg *pWidth, ulg *pHeight) 89 { 90 uch sig[8]; 91 92 93 /* first do a quick check that the file really is a PNG image; could 94 * have used slightly more general png_sig_cmp() function instead */ 95 96 fread(sig, 1, 8, infile); 97 if (png_sig_cmp(sig, 0, 8)) 98 return 1; /* bad signature */ 99 100 101 /* could pass pointers to user-defined error handlers instead of NULLs: */ 102 103 png_ptr = png_create_read_struct(png_get_libpng_ver(NULL), NULL, NULL, 104 NULL); 105 if (!png_ptr) 106 return 4; /* out of memory */ 107 108 info_ptr = png_create_info_struct(png_ptr); 109 if (!info_ptr) { 110 png_destroy_read_struct(&png_ptr, NULL, NULL); 111 return 4; /* out of memory */ 112 } 113 114 115 /* we could create a second info struct here (end_info), but it's only 116 * useful if we want to keep pre- and post-IDAT chunk info separated 117 * (mainly for PNG-aware image editors and converters) */ 118 119 120 /* setjmp() must be called in every function that calls a PNG-reading 121 * libpng function */ 122 123 if (setjmp(png_jmpbuf(png_ptr))) { 124 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 125 return 2; 126 } 127 128 129 png_init_io(png_ptr, infile); 130 png_set_sig_bytes(png_ptr, 8); /* we already read the 8 signature bytes */ 131 132 png_read_info(png_ptr, info_ptr); /* read all PNG info up to image data */ 133 134 135 /* alternatively, could make separate calls to png_get_image_width(), 136 * etc., but want bit_depth and color_type for later [don't care about 137 * compression_type and filter_type => NULLs] */ 138 139 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 140 NULL, NULL, NULL); 141 *pWidth = width; 142 *pHeight = height; 143 144 145 /* OK, that's all we need for now; return happy */ 146 147 return 0; 148 } 149 150 151 152 153 /* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error; 154 * scales values to 8-bit if necessary */ 155 156 int readpng_get_bgcolor(uch *red, uch *green, uch *blue) 157 { 158 png_color_16p pBackground; 159 160 161 /* setjmp() must be called in every function that calls a PNG-reading 162 * libpng function */ 163 164 if (setjmp(png_jmpbuf(png_ptr))) { 165 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 166 return 2; 167 } 168 169 170 if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD)) 171 return 1; 172 173 /* it is not obvious from the libpng documentation, but this function 174 * takes a pointer to a pointer, and it always returns valid red, green 175 * and blue values, regardless of color_type: */ 176 177 png_get_bKGD(png_ptr, info_ptr, &pBackground); 178 179 180 /* however, it always returns the raw bKGD data, regardless of any 181 * bit-depth transformations, so check depth and adjust if necessary */ 182 183 if (bit_depth == 16) { 184 *red = pBackground->red >> 8; 185 *green = pBackground->green >> 8; 186 *blue = pBackground->blue >> 8; 187 } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) { 188 if (bit_depth == 1) 189 *red = *green = *blue = pBackground->gray? 255 : 0; 190 else if (bit_depth == 2) 191 *red = *green = *blue = (255/3) * pBackground->gray; 192 else /* bit_depth == 4 */ 193 *red = *green = *blue = (255/15) * pBackground->gray; 194 } else { 195 *red = (uch)pBackground->red; 196 *green = (uch)pBackground->green; 197 *blue = (uch)pBackground->blue; 198 } 199 200 return 0; 201 } 202 203 204 205 206 /* display_exponent == LUT_exponent * CRT_exponent */ 207 208 uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes) 209 { 210 double gamma; 211 png_uint_32 i, rowbytes; 212 png_bytepp row_pointers = NULL; 213 214 215 /* setjmp() must be called in every function that calls a PNG-reading 216 * libpng function */ 217 218 if (setjmp(png_jmpbuf(png_ptr))) { 219 free(image_data); 220 image_data = NULL; 221 free(row_pointers); 222 row_pointers = NULL; 223 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 224 return NULL; 225 } 226 227 228 /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits, 229 * transparency chunks to full alpha channel; strip 16-bit-per-sample 230 * images to 8 bits per sample; and convert grayscale to RGB[A] */ 231 232 if (color_type == PNG_COLOR_TYPE_PALETTE) 233 png_set_expand(png_ptr); 234 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 235 png_set_expand(png_ptr); 236 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 237 png_set_expand(png_ptr); 238 #ifdef PNG_READ_16_TO_8_SUPPORTED 239 if (bit_depth == 16) 240 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED 241 png_set_scale_16(png_ptr); 242 # else 243 png_set_strip_16(png_ptr); 244 # endif 245 #endif 246 if (color_type == PNG_COLOR_TYPE_GRAY || 247 color_type == PNG_COLOR_TYPE_GRAY_ALPHA) 248 png_set_gray_to_rgb(png_ptr); 249 250 251 /* unlike the example in the libpng documentation, we have *no* idea where 252 * this file may have come from--so if it doesn't have a file gamma, don't 253 * do any correction ("do no harm") */ 254 255 if (png_get_gAMA(png_ptr, info_ptr, &gamma)) 256 png_set_gamma(png_ptr, display_exponent, gamma); 257 258 259 /* all transformations have been registered; now update info_ptr data, 260 * get rowbytes and channels, and allocate image memory */ 261 262 png_read_update_info(png_ptr, info_ptr); 263 264 *pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr); 265 *pChannels = (int)png_get_channels(png_ptr, info_ptr); 266 267 if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) { 268 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 269 return NULL; 270 } 271 if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) { 272 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 273 free(image_data); 274 image_data = NULL; 275 return NULL; 276 } 277 278 Trace((stderr, "readpng_get_image: channels = %d, rowbytes = %ld, height = %ld\n", 279 *pChannels, rowbytes, height)); 280 281 282 /* set the individual row_pointers to point at the correct offsets */ 283 284 for (i = 0; i < height; ++i) 285 row_pointers[i] = image_data + i*rowbytes; 286 287 288 /* now we can go ahead and just read the whole image */ 289 290 png_read_image(png_ptr, row_pointers); 291 292 293 /* and we're done! (png_read_end() can be omitted if no processing of 294 * post-IDAT text/time/etc. is desired) */ 295 296 free(row_pointers); 297 row_pointers = NULL; 298 299 png_read_end(png_ptr, NULL); 300 301 return image_data; 302 } 303 304 305 void readpng_cleanup(int free_image_data) 306 { 307 if (free_image_data && image_data) { 308 free(image_data); 309 image_data = NULL; 310 } 311 312 if (png_ptr && info_ptr) { 313 png_destroy_read_struct(&png_ptr, &info_ptr, NULL); 314 png_ptr = NULL; 315 info_ptr = NULL; 316 } 317 } 318
