pngenc.c
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1 /*
2  * PNG image format
3  * Copyright (c) 2003 Fabrice Bellard
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 #include "avcodec.h"
22 #include "bytestream.h"
23 #include "dsputil.h"
24 #include "png.h"
25 
26 /* TODO:
27  * - add 2, 4 and 16 bit depth support
28  */
29 
30 #include <zlib.h>
31 
32 //#define DEBUG
33 
34 #define IOBUF_SIZE 4096
35 
36 typedef struct PNGEncContext {
38 
39  uint8_t *bytestream;
40  uint8_t *bytestream_start;
41  uint8_t *bytestream_end;
43 
45 
46  z_stream zstream;
47  uint8_t buf[IOBUF_SIZE];
49 
50 static void png_get_interlaced_row(uint8_t *dst, int row_size,
51  int bits_per_pixel, int pass,
52  const uint8_t *src, int width)
53 {
54  int x, mask, dst_x, j, b, bpp;
55  uint8_t *d;
56  const uint8_t *s;
57 
58  mask = ff_png_pass_mask[pass];
59  switch(bits_per_pixel) {
60  case 1:
61  memset(dst, 0, row_size);
62  dst_x = 0;
63  for(x = 0; x < width; x++) {
64  j = (x & 7);
65  if ((mask << j) & 0x80) {
66  b = (src[x >> 3] >> (7 - j)) & 1;
67  dst[dst_x >> 3] |= b << (7 - (dst_x & 7));
68  dst_x++;
69  }
70  }
71  break;
72  default:
73  bpp = bits_per_pixel >> 3;
74  d = dst;
75  s = src;
76  for(x = 0; x < width; x++) {
77  j = x & 7;
78  if ((mask << j) & 0x80) {
79  memcpy(d, s, bpp);
80  d += bpp;
81  }
82  s += bpp;
83  }
84  break;
85  }
86 }
87 
88 static void sub_png_paeth_prediction(uint8_t *dst, uint8_t *src, uint8_t *top, int w, int bpp)
89 {
90  int i;
91  for(i = 0; i < w; i++) {
92  int a, b, c, p, pa, pb, pc;
93 
94  a = src[i - bpp];
95  b = top[i];
96  c = top[i - bpp];
97 
98  p = b - c;
99  pc = a - c;
100 
101  pa = abs(p);
102  pb = abs(pc);
103  pc = abs(p + pc);
104 
105  if (pa <= pb && pa <= pc)
106  p = a;
107  else if (pb <= pc)
108  p = b;
109  else
110  p = c;
111  dst[i] = src[i] - p;
112  }
113 }
114 
115 static void png_filter_row(DSPContext *dsp, uint8_t *dst, int filter_type,
116  uint8_t *src, uint8_t *top, int size, int bpp)
117 {
118  int i;
119 
120  switch(filter_type) {
122  memcpy(dst, src, size);
123  break;
125  dsp->diff_bytes(dst, src, src-bpp, size);
126  memcpy(dst, src, bpp);
127  break;
128  case PNG_FILTER_VALUE_UP:
129  dsp->diff_bytes(dst, src, top, size);
130  break;
132  for(i = 0; i < bpp; i++)
133  dst[i] = src[i] - (top[i] >> 1);
134  for(; i < size; i++)
135  dst[i] = src[i] - ((src[i-bpp] + top[i]) >> 1);
136  break;
138  for(i = 0; i < bpp; i++)
139  dst[i] = src[i] - top[i];
140  sub_png_paeth_prediction(dst+i, src+i, top+i, size-i, bpp);
141  break;
142  }
143 }
144 
145 static uint8_t *png_choose_filter(PNGEncContext *s, uint8_t *dst,
146  uint8_t *src, uint8_t *top, int size, int bpp)
147 {
148  int pred = s->filter_type;
149  assert(bpp || !pred);
150  if(!top && pred)
151  pred = PNG_FILTER_VALUE_SUB;
152  if(pred == PNG_FILTER_VALUE_MIXED) {
153  int i;
154  int cost, bcost = INT_MAX;
155  uint8_t *buf1 = dst, *buf2 = dst + size + 16;
156  for(pred=0; pred<5; pred++) {
157  png_filter_row(&s->dsp, buf1+1, pred, src, top, size, bpp);
158  buf1[0] = pred;
159  cost = 0;
160  for(i=0; i<=size; i++)
161  cost += abs((int8_t)buf1[i]);
162  if(cost < bcost) {
163  bcost = cost;
164  FFSWAP(uint8_t*, buf1, buf2);
165  }
166  }
167  return buf2;
168  } else {
169  png_filter_row(&s->dsp, dst+1, pred, src, top, size, bpp);
170  dst[0] = pred;
171  return dst;
172  }
173 }
174 
175 static void convert_from_rgb32(uint8_t *dst, const uint8_t *src, int width)
176 {
177  uint8_t *d;
178  int j;
179  unsigned int v;
180 
181  d = dst;
182  for(j = 0; j < width; j++) {
183  v = ((const uint32_t *)src)[j];
184  d[0] = v >> 16;
185  d[1] = v >> 8;
186  d[2] = v;
187  d[3] = v >> 24;
188  d += 4;
189  }
190 }
191 
192 static void png_write_chunk(uint8_t **f, uint32_t tag,
193  const uint8_t *buf, int length)
194 {
195  uint32_t crc;
196  uint8_t tagbuf[4];
197 
198  bytestream_put_be32(f, length);
199  crc = crc32(0, Z_NULL, 0);
200  AV_WL32(tagbuf, tag);
201  crc = crc32(crc, tagbuf, 4);
202  bytestream_put_be32(f, av_bswap32(tag));
203  if (length > 0) {
204  crc = crc32(crc, buf, length);
205  memcpy(*f, buf, length);
206  *f += length;
207  }
208  bytestream_put_be32(f, crc);
209 }
210 
211 /* XXX: do filtering */
212 static int png_write_row(PNGEncContext *s, const uint8_t *data, int size)
213 {
214  int ret;
215 
216  s->zstream.avail_in = size;
217  s->zstream.next_in = (uint8_t *)data;
218  while (s->zstream.avail_in > 0) {
219  ret = deflate(&s->zstream, Z_NO_FLUSH);
220  if (ret != Z_OK)
221  return -1;
222  if (s->zstream.avail_out == 0) {
223  if(s->bytestream_end - s->bytestream > IOBUF_SIZE + 100)
224  png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, IOBUF_SIZE);
225  s->zstream.avail_out = IOBUF_SIZE;
226  s->zstream.next_out = s->buf;
227  }
228  }
229  return 0;
230 }
231 
232 static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size, void *data){
233  PNGEncContext *s = avctx->priv_data;
234  AVFrame *pict = data;
235  AVFrame * const p= &s->picture;
236  int bit_depth, color_type, y, len, row_size, ret, is_progressive;
237  int bits_per_pixel, pass_row_size;
238  int compression_level;
239  uint8_t *ptr, *top;
240  uint8_t *crow_base = NULL, *crow_buf, *crow;
241  uint8_t *progressive_buf = NULL;
242  uint8_t *rgba_buf = NULL;
243  uint8_t *top_buf = NULL;
244 
245  *p = *pict;
247  p->key_frame= 1;
248 
249  s->bytestream_start=
250  s->bytestream= buf;
251  s->bytestream_end= buf+buf_size;
252 
253  is_progressive = !!(avctx->flags & CODEC_FLAG_INTERLACED_DCT);
254  switch(avctx->pix_fmt) {
255  case PIX_FMT_RGB32:
256  bit_depth = 8;
257  color_type = PNG_COLOR_TYPE_RGB_ALPHA;
258  break;
259  case PIX_FMT_RGB24:
260  bit_depth = 8;
261  color_type = PNG_COLOR_TYPE_RGB;
262  break;
263  case PIX_FMT_GRAY8:
264  bit_depth = 8;
265  color_type = PNG_COLOR_TYPE_GRAY;
266  break;
267  case PIX_FMT_MONOBLACK:
268  bit_depth = 1;
269  color_type = PNG_COLOR_TYPE_GRAY;
270  break;
271  case PIX_FMT_PAL8:
272  bit_depth = 8;
273  color_type = PNG_COLOR_TYPE_PALETTE;
274  break;
275  default:
276  return -1;
277  }
278  bits_per_pixel = ff_png_get_nb_channels(color_type) * bit_depth;
279  row_size = (avctx->width * bits_per_pixel + 7) >> 3;
280 
281  s->zstream.zalloc = ff_png_zalloc;
282  s->zstream.zfree = ff_png_zfree;
283  s->zstream.opaque = NULL;
284  compression_level = avctx->compression_level == FF_COMPRESSION_DEFAULT ?
285  Z_DEFAULT_COMPRESSION :
286  av_clip(avctx->compression_level, 0, 9);
287  ret = deflateInit2(&s->zstream, compression_level,
288  Z_DEFLATED, 15, 8, Z_DEFAULT_STRATEGY);
289  if (ret != Z_OK)
290  return -1;
291  crow_base = av_malloc((row_size + 32) << (s->filter_type == PNG_FILTER_VALUE_MIXED));
292  if (!crow_base)
293  goto fail;
294  crow_buf = crow_base + 15; // pixel data should be aligned, but there's a control byte before it
295  if (is_progressive) {
296  progressive_buf = av_malloc(row_size + 1);
297  if (!progressive_buf)
298  goto fail;
299  }
300  if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
301  rgba_buf = av_malloc(row_size + 1);
302  if (!rgba_buf)
303  goto fail;
304  }
305  if (is_progressive || color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
306  top_buf = av_malloc(row_size + 1);
307  if (!top_buf)
308  goto fail;
309  }
310 
311  /* write png header */
312  memcpy(s->bytestream, ff_pngsig, 8);
313  s->bytestream += 8;
314 
315  AV_WB32(s->buf, avctx->width);
316  AV_WB32(s->buf + 4, avctx->height);
317  s->buf[8] = bit_depth;
318  s->buf[9] = color_type;
319  s->buf[10] = 0; /* compression type */
320  s->buf[11] = 0; /* filter type */
321  s->buf[12] = is_progressive; /* interlace type */
322 
323  png_write_chunk(&s->bytestream, MKTAG('I', 'H', 'D', 'R'), s->buf, 13);
324 
325  /* put the palette if needed */
326  if (color_type == PNG_COLOR_TYPE_PALETTE) {
327  int has_alpha, alpha, i;
328  unsigned int v;
329  uint32_t *palette;
330  uint8_t *alpha_ptr;
331 
332  palette = (uint32_t *)p->data[1];
333  ptr = s->buf;
334  alpha_ptr = s->buf + 256 * 3;
335  has_alpha = 0;
336  for(i = 0; i < 256; i++) {
337  v = palette[i];
338  alpha = v >> 24;
339  if (alpha && alpha != 0xff)
340  has_alpha = 1;
341  *alpha_ptr++ = alpha;
342  bytestream_put_be24(&ptr, v);
343  }
344  png_write_chunk(&s->bytestream, MKTAG('P', 'L', 'T', 'E'), s->buf, 256 * 3);
345  if (has_alpha) {
346  png_write_chunk(&s->bytestream, MKTAG('t', 'R', 'N', 'S'), s->buf + 256 * 3, 256);
347  }
348  }
349 
350  /* now put each row */
351  s->zstream.avail_out = IOBUF_SIZE;
352  s->zstream.next_out = s->buf;
353  if (is_progressive) {
354  int pass;
355 
356  for(pass = 0; pass < NB_PASSES; pass++) {
357  /* NOTE: a pass is completely omited if no pixels would be
358  output */
359  pass_row_size = ff_png_pass_row_size(pass, bits_per_pixel, avctx->width);
360  if (pass_row_size > 0) {
361  top = NULL;
362  for(y = 0; y < avctx->height; y++) {
363  if ((ff_png_pass_ymask[pass] << (y & 7)) & 0x80) {
364  ptr = p->data[0] + y * p->linesize[0];
365  FFSWAP(uint8_t*, progressive_buf, top_buf);
366  if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
367  convert_from_rgb32(rgba_buf, ptr, avctx->width);
368  ptr = rgba_buf;
369  }
370  png_get_interlaced_row(progressive_buf, pass_row_size,
371  bits_per_pixel, pass,
372  ptr, avctx->width);
373  crow = png_choose_filter(s, crow_buf, progressive_buf, top, pass_row_size, bits_per_pixel>>3);
374  png_write_row(s, crow, pass_row_size + 1);
375  top = progressive_buf;
376  }
377  }
378  }
379  }
380  } else {
381  top = NULL;
382  for(y = 0; y < avctx->height; y++) {
383  ptr = p->data[0] + y * p->linesize[0];
384  if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
385  FFSWAP(uint8_t*, rgba_buf, top_buf);
386  convert_from_rgb32(rgba_buf, ptr, avctx->width);
387  ptr = rgba_buf;
388  }
389  crow = png_choose_filter(s, crow_buf, ptr, top, row_size, bits_per_pixel>>3);
390  png_write_row(s, crow, row_size + 1);
391  top = ptr;
392  }
393  }
394  /* compress last bytes */
395  for(;;) {
396  ret = deflate(&s->zstream, Z_FINISH);
397  if (ret == Z_OK || ret == Z_STREAM_END) {
398  len = IOBUF_SIZE - s->zstream.avail_out;
399  if (len > 0 && s->bytestream_end - s->bytestream > len + 100) {
400  png_write_chunk(&s->bytestream, MKTAG('I', 'D', 'A', 'T'), s->buf, len);
401  }
402  s->zstream.avail_out = IOBUF_SIZE;
403  s->zstream.next_out = s->buf;
404  if (ret == Z_STREAM_END)
405  break;
406  } else {
407  goto fail;
408  }
409  }
410  png_write_chunk(&s->bytestream, MKTAG('I', 'E', 'N', 'D'), NULL, 0);
411 
412  ret = s->bytestream - s->bytestream_start;
413  the_end:
414  av_free(crow_base);
415  av_free(progressive_buf);
416  av_free(rgba_buf);
417  av_free(top_buf);
418  deflateEnd(&s->zstream);
419  return ret;
420  fail:
421  ret = -1;
422  goto the_end;
423 }
424 
426  PNGEncContext *s = avctx->priv_data;
427 
429  avctx->coded_frame= &s->picture;
430  dsputil_init(&s->dsp, avctx);
431 
433  if(avctx->pix_fmt == PIX_FMT_MONOBLACK)
435 
436  return 0;
437 }
438 
440  .name = "png",
441  .type = AVMEDIA_TYPE_VIDEO,
442  .id = CODEC_ID_PNG,
443  .priv_data_size = sizeof(PNGEncContext),
444  .init = png_enc_init,
445  .encode = encode_frame,
447  .long_name= NULL_IF_CONFIG_SMALL("PNG image"),
448 };