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_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
155int 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
207uch *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
304void 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