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
69static png_structp png_ptr = NULL;
70static png_infop info_ptr = NULL;
71
72png_uint_32  width, height;
73int  bit_depth, color_type;
74uch  *image_data = NULL;
75
76
77void 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
88int 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
156int 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
208uch *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
305void 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