source/libs/libpng/libpng-src/contrib/gregbook/readpng.c

   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 }