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
readpng_version_info(void)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
readpng_init(FILE * infile,ulg * pWidth,ulg * pHeight)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
readpng_get_bgcolor(uch * red,uch * green,uch * blue)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
readpng_get_image(double display_exponent,int * pChannels,ulg * pRowbytes)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
readpng_cleanup(int free_image_data)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