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FFmpeg/libavformat/gifdec.c

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  1. /*

  2.  * GIF decoder

  3.  * Copyright (c) 2003 Fabrice Bellard.

  4.  *

  5.  * This library is free software; you can redistribute it and/or

  6.  * modify it under the terms of the GNU Lesser General Public

  7.  * License as published by the Free Software Foundation; either

  8.  * version 2 of the License, or (at your option) any later version.

  9.  *

  10.  * This library is distributed in the hope that it will be useful,

  11.  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  12.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  13.  * Lesser General Public License for more details.

  14.  *

  15.  * You should have received a copy of the GNU Lesser General Public

  16.  * License along with this library; if not, write to the Free Software

  17.  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  18.  */

  19. #include "avformat.h"

  20. 

  21. int gif_write(ByteIOContext *pb, AVImageInfo *info);

  22. 

  23. //#define DEBUG

  24. 

  25. #define MAXBITS		12

  26. #define	SIZTABLE	(1<<MAXBITS)

  27. 

  28. #define GCE_DISPOSAL_NONE       0

  29. #define GCE_DISPOSAL_INPLACE    1

  30. #define GCE_DISPOSAL_BACKGROUND 2

  31. #define GCE_DISPOSAL_RESTORE    3

  32. 

  33. typedef struct GifState {

  34.     int screen_width;

  35.     int screen_height;

  36.     int bits_per_pixel;

  37.     int background_color_index;

  38.     int transparent_color_index;

  39.     int color_resolution;

  40.     uint8_t *image_buf;

  41.     int image_linesize;

  42.     uint32_t *image_palette;

  43.     int pix_fmt;

  44. 

  45.     /* after the frame is displayed, the disposal method is used */

  46.     int gce_disposal;

  47.     /* delay during which the frame is shown */

  48.     int gce_delay;

  49.     

  50.     /* LZW compatible decoder */

  51.     ByteIOContext *f;

  52.     int eob_reached;

  53.     uint8_t *pbuf, *ebuf;

  54.     int bbits;

  55.     unsigned int bbuf;

  56. 

  57.     int cursize;		/* The current code size */

  58.     int curmask;

  59.     int codesize;

  60.     int clear_code;

  61.     int end_code;

  62.     int newcodes;		/* First available code */

  63.     int top_slot;		/* Highest code for current size */

  64.     int slot;			/* Last read code */

  65.     int fc, oc;

  66.     uint8_t *sp;

  67.     uint8_t stack[SIZTABLE];

  68.     uint8_t suffix[SIZTABLE];

  69.     uint16_t prefix[SIZTABLE];

  70. 

  71.     /* aux buffers */

  72.     uint8_t global_palette[256 * 3];

  73.     uint8_t local_palette[256 * 3];

  74.     uint8_t buf[256];

  75. } GifState;

  76. 

  77. 

  78. static const uint8_t gif87a_sig[6] = "GIF87a";

  79. static const uint8_t gif89a_sig[6] = "GIF89a";

  80. 

  81. static const uint16_t mask[17] =

  82. {

  83.     0x0000, 0x0001, 0x0003, 0x0007,

  84.     0x000F, 0x001F, 0x003F, 0x007F,

  85.     0x00FF, 0x01FF, 0x03FF, 0x07FF,

  86.     0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF

  87. };

  88. 

  89. /* Probe gif video format or gif image format. The current heuristic

  90.    supposes the gif87a is always a single image. For gif89a, we

  91.    consider it as a video only if a GCE extension is present in the

  92.    first kilobyte. */

  93. static int gif_video_probe(AVProbeData * pd)

  94. {

  95.     const uint8_t *p, *p_end;

  96.     int bits_per_pixel, has_global_palette, ext_code, ext_len;

  97.     int gce_flags, gce_disposal;

  98. 

  99.     if (pd->buf_size < 24 ||

  100. 	memcmp(pd->buf, gif89a_sig, 6) != 0)

  101.         return 0;

  102.     p_end = pd->buf + pd->buf_size;

  103.     p = pd->buf + 6;

  104.     bits_per_pixel = (p[4] & 0x07) + 1;

  105.     has_global_palette = (p[4] & 0x80);

  106.     p += 7;

  107.     if (has_global_palette)

  108.         p += (1 << bits_per_pixel) * 3;

  109.     for(;;) {

  110.         if (p >= p_end)

  111.             return 0;

  112.         if (*p != '!')

  113.             break;

  114.         p++;

  115.         if (p >= p_end)

  116.             return 0;

  117.         ext_code = *p++;

  118.         if (p >= p_end)

  119.             return 0;

  120.         ext_len = *p++;

  121.         if (ext_code == 0xf9) {

  122.             if (p >= p_end)

  123.                 return 0;

  124.             /* if GCE extension found with gce_disposal != 0: it is

  125.                likely to be an animation */

  126.             gce_flags = *p++;

  127.             gce_disposal = (gce_flags >> 2) & 0x7;

  128.             if (gce_disposal != 0)

  129.                 return AVPROBE_SCORE_MAX;

  130.             else

  131.                 return 0;

  132.         }

  133.         for(;;) {

  134.             if (ext_len == 0)

  135.                 break;

  136.             p += ext_len;

  137.             if (p >= p_end)

  138.                 return 0;

  139.             ext_len = *p++;

  140.         }

  141.     }

  142.     return 0;

  143. }

  144. 

  145. static int gif_image_probe(AVProbeData * pd)

  146. {

  147.     if (pd->buf_size >= 24 &&

  148. 	(memcmp(pd->buf, gif87a_sig, 6) == 0 ||

  149. 	 memcmp(pd->buf, gif89a_sig, 6) == 0))

  150. 	return AVPROBE_SCORE_MAX - 1;

  151.     else

  152. 	return 0;

  153. }

  154. 

  155. 

  156. static void GLZWDecodeInit(GifState * s, int csize)

  157. {

  158.     /* read buffer */

  159.     s->eob_reached = 0;

  160.     s->pbuf = s->buf;

  161.     s->ebuf = s->buf;

  162.     s->bbuf = 0;

  163.     s->bbits = 0;

  164. 

  165.     /* decoder */

  166.     s->codesize = csize;

  167.     s->cursize = s->codesize + 1;

  168.     s->curmask = mask[s->cursize];

  169.     s->top_slot = 1 << s->cursize;

  170.     s->clear_code = 1 << s->codesize;

  171.     s->end_code = s->clear_code + 1;

  172.     s->slot = s->newcodes = s->clear_code + 2;

  173.     s->oc = s->fc = 0;

  174.     s->sp = s->stack;

  175. }

  176. 

  177. /* XXX: optimize */

  178. static inline int GetCode(GifState * s)

  179. {

  180.     int c, sizbuf;

  181.     uint8_t *ptr;

  182. 

  183.     while (s->bbits < s->cursize) {

  184.         ptr = s->pbuf;

  185.         if (ptr >= s->ebuf) {

  186.             if (!s->eob_reached) {

  187.                 sizbuf = get_byte(s->f);

  188.                 s->ebuf = s->buf + sizbuf;

  189.                 s->pbuf = s->buf;

  190.                 if (sizbuf > 0) {

  191.                     get_buffer(s->f, s->buf, sizbuf);

  192.                 } else {

  193.                     s->eob_reached = 1;

  194.                 }

  195.             }

  196.             ptr = s->pbuf;

  197.         }

  198.         s->bbuf |= ptr[0] << s->bbits;

  199.         ptr++;

  200.         s->pbuf = ptr;

  201. 	s->bbits += 8;

  202.     }

  203.     c = s->bbuf & s->curmask;

  204.     s->bbuf >>= s->cursize;

  205.     s->bbits -= s->cursize;

  206.     return c;

  207. }

  208. 

  209. /* NOTE: the algorithm here is inspired from the LZW GIF decoder

  210.    written by Steven A. Bennett in 1987. */

  211. /* return the number of byte decoded */

  212. static int GLZWDecode(GifState * s, uint8_t * buf, int len)

  213. {

  214.     int l, c, code, oc, fc;

  215.     uint8_t *sp;

  216. 

  217.     if (s->end_code < 0)

  218.         return 0;

  219. 

  220.     l = len;

  221.     sp = s->sp;

  222.     oc = s->oc;

  223.     fc = s->fc;

  224. 

  225.     while (sp > s->stack) {

  226. 	*buf++ = *(--sp);

  227. 	if ((--l) == 0)

  228. 	    goto the_end;

  229.     }

  230. 

  231.     for (;;) {

  232. 	c = GetCode(s);

  233. 	if (c == s->end_code) {

  234. 	    s->end_code = -1;

  235. 	    break;

  236. 	} else if (c == s->clear_code) {

  237. 	    s->cursize = s->codesize + 1;

  238. 	    s->curmask = mask[s->cursize];

  239. 	    s->slot = s->newcodes;

  240. 	    s->top_slot = 1 << s->cursize;

  241. 	    while ((c = GetCode(s)) == s->clear_code);

  242. 	    if (c == s->end_code) {

  243. 		s->end_code = -1;

  244. 		break;

  245. 	    }

  246. 	    /* test error */

  247. 	    if (c >= s->slot)

  248. 		c = 0;

  249. 	    fc = oc = c;

  250. 	    *buf++ = c;

  251. 	    if ((--l) == 0)

  252. 		break;

  253. 	} else {

  254. 	    code = c;

  255. 	    if (code >= s->slot) {

  256. 		*sp++ = fc;

  257. 		code = oc;

  258. 	    }

  259. 	    while (code >= s->newcodes) {

  260. 		*sp++ = s->suffix[code];

  261. 		code = s->prefix[code];

  262. 	    }

  263. 	    *sp++ = code;

  264. 	    if (s->slot < s->top_slot) {

  265. 		s->suffix[s->slot] = fc = code;

  266. 		s->prefix[s->slot++] = oc;

  267. 		oc = c;

  268. 	    }

  269. 	    if (s->slot >= s->top_slot) {

  270. 		if (s->cursize < MAXBITS) {

  271. 		    s->top_slot <<= 1;

  272. 		    s->curmask = mask[++s->cursize];

  273. 		}

  274. 	    }

  275. 	    while (sp > s->stack) {

  276. 		*buf++ = *(--sp);

  277. 		if ((--l) == 0)

  278.                     goto the_end;

  279. 	    }

  280. 	}

  281.     }

  282.   the_end:

  283.     s->sp = sp;

  284.     s->oc = oc;

  285.     s->fc = fc;

  286.     return len - l;

  287. }

  288. 

  289. static int gif_read_image(GifState *s)

  290. {

  291.     ByteIOContext *f = s->f;

  292.     int left, top, width, height, bits_per_pixel, code_size, flags;

  293.     int is_interleaved, has_local_palette, y, x, pass, y1, linesize, n, i;

  294.     uint8_t *ptr, *line, *d, *spal, *palette, *sptr, *ptr1;

  295. 

  296.     left = get_le16(f);

  297.     top = get_le16(f);

  298.     width = get_le16(f);

  299.     height = get_le16(f);

  300.     flags = get_byte(f);

  301.     is_interleaved = flags & 0x40;

  302.     has_local_palette = flags & 0x80;

  303.     bits_per_pixel = (flags & 0x07) + 1;

  304. #ifdef DEBUG

  305.     printf("gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);

  306. #endif

  307. 

  308.     if (has_local_palette) {

  309. 	get_buffer(f, s->local_palette, 3 * (1 << bits_per_pixel));

  310.         palette = s->local_palette;

  311.     } else {

  312.         palette = s->global_palette;

  313.         bits_per_pixel = s->bits_per_pixel;

  314.     }

  315.     

  316.     /* verify that all the image is inside the screen dimensions */

  317.     if (left + width > s->screen_width ||

  318.         top + height > s->screen_height)

  319.         return -EINVAL;

  320. 

  321.     /* build the palette */

  322.     if (s->pix_fmt == PIX_FMT_RGB24) {

  323.         line = av_malloc(width);

  324.         if (!line)

  325.             return -ENOMEM;

  326.     } else {

  327.         n = (1 << bits_per_pixel);

  328.         spal = palette;

  329.         for(i = 0; i < n; i++) {

  330.             s->image_palette[i] = (0xff << 24) | 

  331.                 (spal[0] << 16) | (spal[1] << 8) | (spal[2]);

  332.             spal += 3;

  333.         }

  334.         for(; i < 256; i++)

  335.             s->image_palette[i] = (0xff << 24);

  336.         /* handle transparency */

  337.         if (s->transparent_color_index >= 0)

  338.             s->image_palette[s->transparent_color_index] = 0;

  339.         line = NULL;

  340.     }

  341. 

  342.     /* now get the image data */

  343.     s->f = f;

  344.     code_size = get_byte(f);

  345.     GLZWDecodeInit(s, code_size);

  346. 

  347.     /* read all the image */

  348.     linesize = s->image_linesize;

  349.     ptr1 = s->image_buf + top * linesize + (left * 3);

  350.     ptr = ptr1;

  351.     pass = 0;

  352.     y1 = 0;

  353.     for (y = 0; y < height; y++) {

  354.         if (s->pix_fmt == PIX_FMT_RGB24) {

  355.             /* transcode to RGB24 */

  356.             GLZWDecode(s, line, width);

  357.             d = ptr;

  358.             sptr = line;

  359.             for(x = 0; x < width; x++) {

  360.                 spal = palette + sptr[0] * 3;

  361.                 d[0] = spal[0];

  362.                 d[1] = spal[1];

  363.                 d[2] = spal[2];

  364.                 d += 3;

  365.                 sptr++;

  366.             }

  367.         } else {

  368.             GLZWDecode(s, ptr, width);

  369.         }

  370.         if (is_interleaved) {

  371.             switch(pass) {

  372.             default:

  373.             case 0:

  374.             case 1:

  375.                 y1 += 8;

  376.                 ptr += linesize * 8;

  377.                 if (y1 >= height) {

  378.                     y1 = 4;

  379.                     if (pass == 0) 

  380.                         ptr = ptr1 + linesize * 4;

  381.                     else

  382.                         ptr = ptr1 + linesize * 2;

  383.                     pass++;

  384.                 }

  385.                 break;

  386.             case 2:

  387.                 y1 += 4;

  388.                 ptr += linesize * 4;

  389.                 if (y1 >= height) {

  390.                     y1 = 1;

  391.                     ptr = ptr1 + linesize;

  392.                     pass++;

  393.                 }

  394.                 break;

  395.             case 3:

  396.                 y1 += 2;

  397.                 ptr += linesize * 2;

  398.                 break;

  399.             }

  400.         } else {

  401.             ptr += linesize;

  402.         }

  403.     }

  404.     av_free(line);

  405.     

  406.     /* read the garbage data until end marker is found */

  407.     while (!s->eob_reached)

  408.         GetCode(s);

  409.     return 0;

  410. }

  411. 

  412. static int gif_read_extension(GifState *s)

  413. {

  414.     ByteIOContext *f = s->f;

  415.     int ext_code, ext_len, i, gce_flags, gce_transparent_index;

  416. 

  417.     /* extension */

  418.     ext_code = get_byte(f);

  419.     ext_len = get_byte(f);

  420. #ifdef DEBUG

  421.     printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);

  422. #endif

  423.     switch(ext_code) {

  424.     case 0xf9:

  425.         if (ext_len != 4)

  426.             goto discard_ext;

  427.         s->transparent_color_index = -1;

  428.         gce_flags = get_byte(f);

  429.         s->gce_delay = get_le16(f);

  430.         gce_transparent_index = get_byte(f);

  431.         if (gce_flags & 0x01)

  432.             s->transparent_color_index = gce_transparent_index;

  433.         else

  434.             s->transparent_color_index = -1;

  435.         s->gce_disposal = (gce_flags >> 2) & 0x7;

  436. #ifdef DEBUG

  437.         printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n", 

  438.                gce_flags, s->gce_delay, 

  439.                s->transparent_color_index, s->gce_disposal);

  440. #endif

  441.         ext_len = get_byte(f);

  442.         break;

  443.     }

  444.         

  445.     /* NOTE: many extension blocks can come after */

  446.  discard_ext:

  447.     while (ext_len != 0) {

  448.         for (i = 0; i < ext_len; i++)

  449.             get_byte(f);

  450.         ext_len = get_byte(f);

  451. #ifdef DEBUG

  452.         printf("gif: ext_len1=%d\n", ext_len);

  453. #endif

  454.     }

  455.     return 0;

  456. }

  457. 

  458. static int gif_read_header1(GifState *s)

  459. {

  460.     ByteIOContext *f = s->f;

  461.     uint8_t sig[6];

  462.     int ret, v, n;

  463.     int has_global_palette;

  464. 

  465.     /* read gif signature */

  466.     ret = get_buffer(f, sig, 6);

  467.     if (ret != 6)

  468. 	return -1;

  469.     if (memcmp(sig, gif87a_sig, 6) != 0 &&

  470. 	memcmp(sig, gif89a_sig, 6) != 0)

  471. 	return -1;

  472. 

  473.     /* read screen header */

  474.     s->transparent_color_index = -1;

  475.     s->screen_width = get_le16(f);

  476.     s->screen_height = get_le16(f);

  477.     if(   (unsigned)s->screen_width  > 32767 

  478.        || (unsigned)s->screen_height > 32767){

  479.         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");

  480.         return -1;

  481.     } 

  482. 

  483.     v = get_byte(f);

  484.     s->color_resolution = ((v & 0x70) >> 4) + 1;

  485.     has_global_palette = (v & 0x80);

  486.     s->bits_per_pixel = (v & 0x07) + 1;

  487.     s->background_color_index = get_byte(f);

  488.     get_byte(f);		/* ignored */

  489. #ifdef DEBUG

  490.     printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",

  491. 	   s->screen_width, s->screen_height, s->bits_per_pixel,

  492. 	   has_global_palette);

  493. #endif

  494.     if (has_global_palette) {

  495. 	n = 1 << s->bits_per_pixel;

  496. 	get_buffer(f, s->global_palette, n * 3);

  497.     }

  498.     return 0;

  499. }

  500. 

  501. static int gif_parse_next_image(GifState *s)

  502. {

  503.     ByteIOContext *f = s->f;

  504.     int ret, code;

  505. 

  506.     for (;;) {

  507. 	code = url_fgetc(f);

  508. #ifdef DEBUG

  509. 	printf("gif: code=%02x '%c'\n", code, code);

  510. #endif

  511. 	switch (code) {

  512. 	case ',':

  513. 	    if (gif_read_image(s) < 0)

  514. 		return AVERROR_IO;

  515. 	    ret = 0;

  516. 	    goto the_end;

  517. 	case ';':

  518. 	    /* end of image */

  519. 	    ret = AVERROR_IO;

  520. 	    goto the_end;

  521. 	case '!':

  522.             if (gif_read_extension(s) < 0)

  523.                 return AVERROR_IO;

  524. 	    break;

  525. 	case EOF:

  526. 	default:

  527. 	    /* error or errneous EOF */

  528. 	    ret = AVERROR_IO;

  529. 	    goto the_end;

  530. 	}

  531.     }

  532.   the_end:

  533.     return ret;

  534. }

  535. 

  536. static int gif_read_header(AVFormatContext * s1,

  537. 			   AVFormatParameters * ap)

  538. {

  539.     GifState *s = s1->priv_data;

  540.     ByteIOContext *f = &s1->pb;

  541.     AVStream *st;

  542. 

  543.     s->f = f;

  544.     if (gif_read_header1(s) < 0)

  545.         return -1;

  546.     

  547.     /* allocate image buffer */

  548.     s->image_linesize = s->screen_width * 3;

  549.     s->image_buf = av_malloc(s->screen_height * s->image_linesize);

  550.     if (!s->image_buf)

  551.         return -ENOMEM;

  552.     s->pix_fmt = PIX_FMT_RGB24;

  553.     /* now we are ready: build format streams */

  554.     st = av_new_stream(s1, 0);

  555.     if (!st)

  556. 	return -1;

  557. 

  558.     st->codec.codec_type = CODEC_TYPE_VIDEO;

  559.     st->codec.codec_id = CODEC_ID_RAWVIDEO;

  560.     st->codec.time_base.den = 5;

  561.     st->codec.time_base.num = 1;

  562.     /* XXX: check if screen size is always valid */

  563.     st->codec.width = s->screen_width;

  564.     st->codec.height = s->screen_height;

  565.     st->codec.pix_fmt = PIX_FMT_RGB24;

  566.     return 0;

  567. }

  568. 

  569. static int gif_read_packet(AVFormatContext * s1,

  570. 			   AVPacket * pkt)

  571. {

  572.     GifState *s = s1->priv_data;

  573.     int ret;

  574. 

  575.     ret = gif_parse_next_image(s);

  576.     if (ret < 0)

  577.         return ret;

  578. 

  579.     /* XXX: avoid copying */

  580.     if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {

  581. 	return AVERROR_IO;

  582.     }

  583.     pkt->stream_index = 0;

  584.     memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);

  585.     return 0;

  586. }

  587. 

  588. static int gif_read_close(AVFormatContext *s1)

  589. {

  590.     GifState *s = s1->priv_data;

  591.     av_free(s->image_buf);

  592.     return 0;

  593. }

  594. 

  595. /* read gif as image */

  596. static int gif_read(ByteIOContext *f, 

  597.                     int (*alloc_cb)(void *opaque, AVImageInfo *info), void *opaque)

  598. {

  599.     GifState s1, *s = &s1;

  600.     AVImageInfo info1, *info = &info1;

  601.     int ret;

  602. 

  603.     memset(s, 0, sizeof(GifState));

  604.     s->f = f;

  605.     if (gif_read_header1(s) < 0)

  606.         return -1;

  607.     info->width = s->screen_width;

  608.     info->height = s->screen_height;

  609.     info->pix_fmt = PIX_FMT_PAL8;

  610.     ret = alloc_cb(opaque, info);

  611.     if (ret)

  612.         return ret;

  613.     s->image_buf = info->pict.data[0];

  614.     s->image_linesize = info->pict.linesize[0];

  615.     s->image_palette = (uint32_t *)info->pict.data[1];

  616. 

  617.     if (gif_parse_next_image(s) < 0)

  618.         return -1;

  619.     return 0;

  620. }

  621. 

  622. AVInputFormat gif_iformat =

  623. {

  624.     "gif",

  625.     "gif format",

  626.     sizeof(GifState),

  627.     gif_video_probe,

  628.     gif_read_header,

  629.     gif_read_packet,

  630.     gif_read_close,

  631. };

  632. 

  633. AVImageFormat gif_image_format = {

  634.     "gif",

  635.     "gif",

  636.     gif_image_probe,

  637.     gif_read,

  638.     (1 << PIX_FMT_PAL8),

  639.     gif_write,

  640. };