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