1 /*
2 * pnglite.c - pnglite library
3 * For conditions of distribution and use, see copyright notice in pnglite.h
4 */
5
6 #ifdef _STANDALONE
7 #include <sys/cdefs.h>
8 #include <stand.h>
9 #else
10 #include <stdio.h>
11 #include <stdlib.h>
12 #include <sys/types.h>
13 #include <sys/stat.h>
14 #include <fcntl.h>
15 #endif
16 #include <zlib.h>
17 #include "pnglite.h"
18
19 #ifndef abs
20 #define abs(x) ((x) < 0? -(x):(x))
21 #endif
22
23 #define PNG_32b(b, s) ((uint32_t)(b) << (s))
24 #define PNG_U32(b1, b2, b3, b4) \
25 (PNG_32b(b1, 24) | PNG_32b(b2, 16) | PNG_32b(b3, 8) | PNG_32b(b4, 0))
26
27 #define png_IDAT PNG_U32(73, 68, 65, 84)
28 #define png_IEND PNG_U32(73, 69, 78, 68)
29
30 static ssize_t
file_read(png_t * png,void * out,size_t size,size_t numel)31 file_read(png_t *png, void *out, size_t size, size_t numel)
32 {
33 ssize_t result;
34 off_t offset = (off_t)(size * numel);
35
36 if (offset < 0)
37 return (PNG_FILE_ERROR);
38
39 if (!out) {
40 result = lseek(png->fd, offset, SEEK_CUR);
41 } else {
42 result = read(png->fd, out, size * numel);
43 }
44
45 return (result);
46 }
47
48 static int
file_read_ul(png_t * png,unsigned * out)49 file_read_ul(png_t *png, unsigned *out)
50 {
51 uint8_t buf[4];
52
53 if (file_read(png, buf, 1, 4) != 4)
54 return (PNG_FILE_ERROR);
55
56 *out = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
57
58 return (PNG_NO_ERROR);
59 }
60
61 static unsigned
get_ul(uint8_t * buf)62 get_ul(uint8_t *buf)
63 {
64 unsigned result;
65 uint8_t foo[4];
66
67 memcpy(foo, buf, 4);
68
69 result = (foo[0]<<24) | (foo[1]<<16) | (foo[2]<<8) | foo[3];
70
71 return (result);
72 }
73
74 static int
png_get_bpp(png_t * png)75 png_get_bpp(png_t *png)
76 {
77 int bpp;
78
79 switch (png->color_type) {
80 case PNG_GREYSCALE:
81 bpp = 1; break;
82 case PNG_TRUECOLOR:
83 bpp = 3; break;
84 case PNG_INDEXED:
85 bpp = 1; break;
86 case PNG_GREYSCALE_ALPHA:
87 bpp = 2; break;
88 case PNG_TRUECOLOR_ALPHA:
89 bpp = 4; break;
90 default:
91 return (PNG_FILE_ERROR);
92 }
93
94 bpp *= png->depth / 8;
95
96 return (bpp);
97 }
98
99 static int
png_read_ihdr(png_t * png)100 png_read_ihdr(png_t *png)
101 {
102 unsigned length = 0;
103 unsigned orig_crc;
104 unsigned calc_crc;
105 uint8_t ihdr[13+4]; /* length should be 13, make room for type (IHDR) */
106
107 if (file_read_ul(png, &length) != PNG_NO_ERROR)
108 return (PNG_FILE_ERROR);
109
110 if (length != 13)
111 return (PNG_CRC_ERROR);
112
113 if (file_read(png, ihdr, 1, 13+4) != 13+4)
114 return (PNG_EOF_ERROR);
115
116 if (file_read_ul(png, &orig_crc) != PNG_NO_ERROR)
117 return (PNG_FILE_ERROR);
118
119 calc_crc = crc32(0L, Z_NULL, 0);
120 calc_crc = crc32(calc_crc, ihdr, 13+4);
121
122 if (orig_crc != calc_crc) {
123 return (PNG_CRC_ERROR);
124 }
125
126 png->width = get_ul(ihdr+4);
127 png->height = get_ul(ihdr+8);
128 png->depth = ihdr[12];
129 png->color_type = ihdr[13];
130 png->compression_method = ihdr[14];
131 png->filter_method = ihdr[15];
132 png->interlace_method = ihdr[16];
133
134 if (png->color_type == PNG_INDEXED)
135 return (PNG_NOT_SUPPORTED);
136
137 if (png->depth != 8 && png->depth != 16)
138 return (PNG_NOT_SUPPORTED);
139
140 if (png->interlace_method)
141 return (PNG_NOT_SUPPORTED);
142
143 return (PNG_NO_ERROR);
144 }
145
146 void
png_print_info(png_t * png)147 png_print_info(png_t *png)
148 {
149 printf("PNG INFO:\n");
150 printf("\twidth:\t\t%d\n", png->width);
151 printf("\theight:\t\t%d\n", png->height);
152 printf("\tdepth:\t\t%d\n", png->depth);
153 printf("\tcolor:\t\t");
154
155 switch (png->color_type) {
156 case PNG_GREYSCALE:
157 printf("greyscale\n"); break;
158 case PNG_TRUECOLOR:
159 printf("truecolor\n"); break;
160 case PNG_INDEXED:
161 printf("palette\n"); break;
162 case PNG_GREYSCALE_ALPHA:
163 printf("greyscale with alpha\n"); break;
164 case PNG_TRUECOLOR_ALPHA:
165 printf("truecolor with alpha\n"); break;
166 default:
167 printf("unknown, this is not good\n"); break;
168 }
169
170 printf("\tcompression:\t%s\n",
171 png->compression_method?
172 "unknown, this is not good":"inflate/deflate");
173 printf("\tfilter:\t\t%s\n",
174 png->filter_method? "unknown, this is not good":"adaptive");
175 printf("\tinterlace:\t%s\n",
176 png->interlace_method? "interlace":"no interlace");
177 }
178
179 int
png_open(png_t * png,const char * filename)180 png_open(png_t *png, const char *filename)
181 {
182 char header[8];
183 int result;
184
185 png->image = NULL;
186 png->fd = open(filename, O_RDONLY);
187 if (png->fd == -1)
188 return (PNG_FILE_ERROR);
189
190 if (file_read(png, header, 1, 8) != 8) {
191 result = PNG_EOF_ERROR;
192 goto done;
193 }
194
195 if (memcmp(header, "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A", 8) != 0) {
196 result = PNG_HEADER_ERROR;
197 goto done;
198 }
199
200 result = png_read_ihdr(png);
201 if (result == PNG_NO_ERROR) {
202 result = png_get_bpp(png);
203 if (result > 0) {
204 png->bpp = (uint8_t)result;
205 result = PNG_NO_ERROR;
206 }
207 }
208
209 done:
210 if (result == PNG_NO_ERROR) {
211 uint64_t size = png->width * png->height * png->bpp;
212
213 if (size < UINT_MAX)
214 png->image = malloc(size);
215 if (png->image == NULL)
216 result = PNG_MEMORY_ERROR;
217 }
218
219 if (result == PNG_NO_ERROR)
220 result = png_get_data(png, png->image);
221
222 if (result != PNG_NO_ERROR) {
223 free(png->image);
224 (void) close(png->fd);
225 png->fd = -1;
226 return (result);
227 }
228
229 return (result);
230 }
231
232 int
png_close(png_t * png)233 png_close(png_t *png)
234 {
235 (void) close(png->fd);
236 png->fd = -1;
237 free(png->image);
238 png->image = NULL;
239
240 return (PNG_NO_ERROR);
241 }
242
243 static int
png_init_inflate(png_t * png)244 png_init_inflate(png_t *png)
245 {
246 z_stream *stream;
247 png->zs = calloc(1, sizeof (z_stream));
248
249 stream = png->zs;
250
251 if (!stream)
252 return (PNG_MEMORY_ERROR);
253
254 if (inflateInit(stream) != Z_OK) {
255 free(png->zs);
256 png->zs = NULL;
257 return (PNG_ZLIB_ERROR);
258 }
259
260 stream->next_out = png->png_data;
261 stream->avail_out = png->png_datalen;
262
263 return (PNG_NO_ERROR);
264 }
265
266 static int
png_end_inflate(png_t * png)267 png_end_inflate(png_t *png)
268 {
269 z_stream *stream = png->zs;
270 int rc = PNG_NO_ERROR;
271
272 if (!stream)
273 return (PNG_MEMORY_ERROR);
274
275 if (inflateEnd(stream) != Z_OK) {
276 printf("ZLIB says: %s\n", stream->msg);
277 rc = PNG_ZLIB_ERROR;
278 }
279
280 free(png->zs);
281 png->zs = NULL;
282
283 return (rc);
284 }
285
286 static int
png_inflate(png_t * png,uint8_t * data,int len)287 png_inflate(png_t *png, uint8_t *data, int len)
288 {
289 int result;
290 z_stream *stream = png->zs;
291
292 if (!stream)
293 return (PNG_MEMORY_ERROR);
294
295 stream->next_in = data;
296 stream->avail_in = len;
297
298 result = inflate(stream, Z_SYNC_FLUSH);
299
300 if (result != Z_STREAM_END && result != Z_OK) {
301 printf("%s\n", stream->msg);
302 return (PNG_ZLIB_ERROR);
303 }
304
305 if (stream->avail_in != 0)
306 return (PNG_ZLIB_ERROR);
307
308 return (PNG_NO_ERROR);
309 }
310
311 static int
png_read_idat(png_t * png,unsigned length)312 png_read_idat(png_t *png, unsigned length)
313 {
314 unsigned orig_crc;
315 unsigned calc_crc;
316 ssize_t len = length;
317
318 if (!png->readbuf || png->readbuflen < length) {
319 png->readbuf = realloc(png->readbuf, length);
320 png->readbuflen = length;
321 }
322
323 if (!png->readbuf)
324 return (PNG_MEMORY_ERROR);
325
326 if (file_read(png, png->readbuf, 1, length) != len)
327 return (PNG_FILE_ERROR);
328
329 calc_crc = crc32(0L, Z_NULL, 0);
330 calc_crc = crc32(calc_crc, (uint8_t *)"IDAT", 4);
331 calc_crc = crc32(calc_crc, (uint8_t *)png->readbuf, length);
332
333 if (file_read_ul(png, &orig_crc) != PNG_NO_ERROR)
334 return (PNG_FILE_ERROR);
335
336 if (orig_crc != calc_crc)
337 return (PNG_CRC_ERROR);
338
339 return (png_inflate(png, png->readbuf, length));
340 }
341
342 static int
png_process_chunk(png_t * png)343 png_process_chunk(png_t *png)
344 {
345 int result = PNG_NO_ERROR;
346 unsigned type;
347 unsigned length;
348
349 if (file_read_ul(png, &length) != PNG_NO_ERROR)
350 return (PNG_FILE_ERROR);
351
352 if (file_read_ul(png, &type) != PNG_NO_ERROR)
353 return (PNG_FILE_ERROR);
354
355 /*
356 * if we found an idat, all other idats should be followed with no
357 * other chunks in between
358 */
359 if (type == png_IDAT) {
360 if (!png->png_data) { /* first IDAT */
361 png->png_datalen = png->width * png->height *
362 png->bpp + png->height;
363 png->png_data = malloc(png->png_datalen);
364 }
365
366 if (!png->png_data)
367 return (PNG_MEMORY_ERROR);
368
369 if (!png->zs) {
370 result = png_init_inflate(png);
371 if (result != PNG_NO_ERROR)
372 return (result);
373 }
374
375 return (png_read_idat(png, length));
376 } else if (type == png_IEND)
377 return (PNG_DONE);
378 else
379 (void) file_read(png, 0, 1, length + 4); /* unknown chunk */
380
381 return (result);
382 }
383
384 static void
png_filter_sub(unsigned stride,uint8_t * in,uint8_t * out,unsigned len)385 png_filter_sub(unsigned stride, uint8_t *in, uint8_t *out, unsigned len)
386 {
387 unsigned i;
388 uint8_t a = 0;
389
390 for (i = 0; i < len; i++) {
391 if (i >= stride)
392 a = out[i - stride];
393
394 out[i] = in[i] + a;
395 }
396 }
397
398 static void
png_filter_up(unsigned stride __unused,uint8_t * in,uint8_t * out,uint8_t * prev_line,unsigned len)399 png_filter_up(unsigned stride __unused, uint8_t *in, uint8_t *out,
400 uint8_t *prev_line, unsigned len)
401 {
402 unsigned i;
403
404 if (prev_line) {
405 for (i = 0; i < len; i++)
406 out[i] = in[i] + prev_line[i];
407 } else
408 memcpy(out, in, len);
409 }
410
411 static void
png_filter_average(unsigned stride,uint8_t * in,uint8_t * out,uint8_t * prev_line,unsigned len)412 png_filter_average(unsigned stride, uint8_t *in, uint8_t *out,
413 uint8_t *prev_line, unsigned len)
414 {
415 unsigned int i;
416 uint8_t a = 0;
417 uint8_t b = 0;
418 unsigned int sum = 0;
419
420 for (i = 0; i < len; i++) {
421 if (prev_line)
422 b = prev_line[i];
423
424 if (i >= stride)
425 a = out[i - stride];
426
427 sum = a;
428 sum += b;
429
430 out[i] = in[i] + sum/2;
431 }
432 }
433
434 static uint8_t
png_paeth(uint8_t a,uint8_t b,uint8_t c)435 png_paeth(uint8_t a, uint8_t b, uint8_t c)
436 {
437 int p = (int)a + b - c;
438 int pa = abs(p - a);
439 int pb = abs(p - b);
440 int pc = abs(p - c);
441
442 int pr;
443
444 if (pa <= pb && pa <= pc)
445 pr = a;
446 else if (pb <= pc)
447 pr = b;
448 else
449 pr = c;
450
451 return (pr);
452 }
453
454 static void
png_filter_paeth(unsigned stride,uint8_t * in,uint8_t * out,uint8_t * prev_line,unsigned len)455 png_filter_paeth(unsigned stride, uint8_t *in, uint8_t *out, uint8_t *prev_line,
456 unsigned len)
457 {
458 unsigned i;
459 uint8_t a;
460 uint8_t b;
461 uint8_t c;
462
463 for (i = 0; i < len; i++) {
464 if (prev_line && i >= stride) {
465 a = out[i - stride];
466 b = prev_line[i];
467 c = prev_line[i - stride];
468 } else {
469 if (prev_line)
470 b = prev_line[i];
471 else
472 b = 0;
473
474 if (i >= stride)
475 a = out[i - stride];
476 else
477 a = 0;
478
479 c = 0;
480 }
481
482 out[i] = in[i] + png_paeth(a, b, c);
483 }
484 }
485
486 static int
png_unfilter(png_t * png,uint8_t * data)487 png_unfilter(png_t *png, uint8_t *data)
488 {
489 unsigned i;
490 unsigned pos = 0;
491 unsigned outpos = 0;
492 uint8_t *filtered = png->png_data;
493 unsigned stride = png->bpp;
494
495 while (pos < png->png_datalen) {
496 uint8_t filter = filtered[pos];
497
498 pos++;
499
500 if (png->depth == 16) {
501 for (i = 0; i < png->width * stride; i += 2) {
502 *(short *)(filtered+pos+i) =
503 (filtered[pos+i] << 8) | filtered[pos+i+1];
504 }
505 }
506
507 switch (filter) {
508 case 0: /* none */
509 memcpy(data+outpos, filtered+pos, png->width * stride);
510 break;
511 case 1: /* sub */
512 png_filter_sub(stride, filtered+pos, data+outpos,
513 png->width * stride);
514 break;
515 case 2: /* up */
516 if (outpos) {
517 png_filter_up(stride, filtered+pos, data+outpos,
518 data + outpos - (png->width*stride),
519 png->width*stride);
520 } else {
521 png_filter_up(stride, filtered+pos, data+outpos,
522 0, png->width*stride);
523 }
524 break;
525 case 3: /* average */
526 if (outpos) {
527 png_filter_average(stride, filtered+pos,
528 data+outpos,
529 data + outpos - (png->width*stride),
530 png->width*stride);
531 } else {
532 png_filter_average(stride, filtered+pos,
533 data+outpos, 0, png->width*stride);
534 }
535 break;
536 case 4: /* paeth */
537 if (outpos) {
538 png_filter_paeth(stride, filtered+pos,
539 data+outpos,
540 data + outpos - (png->width*stride),
541 png->width*stride);
542 } else {
543 png_filter_paeth(stride, filtered+pos,
544 data+outpos, 0, png->width*stride);
545 }
546 break;
547 default:
548 return (PNG_UNKNOWN_FILTER);
549 }
550
551 outpos += png->width * stride;
552 pos += png->width * stride;
553 }
554
555 return (PNG_NO_ERROR);
556 }
557
558 int
png_get_data(png_t * png,uint8_t * data)559 png_get_data(png_t *png, uint8_t *data)
560 {
561 int result = PNG_NO_ERROR;
562
563 png->zs = NULL;
564 png->png_datalen = 0;
565 png->png_data = NULL;
566 png->readbuf = NULL;
567 png->readbuflen = 0;
568
569 while (result == PNG_NO_ERROR)
570 result = png_process_chunk(png);
571
572 if (png->readbuf) {
573 free(png->readbuf);
574 png->readbuflen = 0;
575 }
576 if (png->zs)
577 (void) png_end_inflate(png);
578
579 if (result != PNG_DONE) {
580 free(png->png_data);
581 return (result);
582 }
583
584 result = png_unfilter(png, data);
585
586 free(png->png_data);
587
588 return (result);
589 }
590
591 char *
png_error_string(int error)592 png_error_string(int error)
593 {
594 switch (error) {
595 case PNG_NO_ERROR:
596 return ("No error");
597 case PNG_FILE_ERROR:
598 return ("Unknown file error.");
599 case PNG_HEADER_ERROR:
600 return ("No PNG header found. Are you sure this is a PNG?");
601 case PNG_IO_ERROR:
602 return ("Failure while reading file.");
603 case PNG_EOF_ERROR:
604 return ("Reached end of file.");
605 case PNG_CRC_ERROR:
606 return ("CRC or chunk length error.");
607 case PNG_MEMORY_ERROR:
608 return ("Could not allocate memory.");
609 case PNG_ZLIB_ERROR:
610 return ("zlib reported an error.");
611 case PNG_UNKNOWN_FILTER:
612 return ("Unknown filter method used in scanline.");
613 case PNG_DONE:
614 return ("PNG done");
615 case PNG_NOT_SUPPORTED:
616 return ("The PNG is unsupported by pnglite, too bad for you!");
617 case PNG_WRONG_ARGUMENTS:
618 return ("Wrong combination of arguments passed to png_open. "
619 "You must use either a read_function or supply a file "
620 "pointer to use.");
621 default:
622 return ("Unknown error.");
623 };
624 }
625