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