/libavcodec/gifdec.c

  1/*
  2 * GIF decoder
  3 * Copyright (c) 2003 Fabrice Bellard
  4 * Copyright (c) 2006 Baptiste Coudurier
  5 * Copyright (c) 2012 Vitaliy E Sugrobov
  6 *
  7 * This file is part of FFmpeg.
  8 *
  9 * FFmpeg is free software; you can redistribute it and/or
 10 * modify it under the terms of the GNU Lesser General Public
 11 * License as published by the Free Software Foundation; either
 12 * version 2.1 of the License, or (at your option) any later version.
 13 *
 14 * FFmpeg is distributed in the hope that it will be useful,
 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 17 * Lesser General Public License for more details.
 18 *
 19 * You should have received a copy of the GNU Lesser General Public
 20 * License along with FFmpeg; if not, write to the Free Software
 21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 22 */
 23
 24#include "libavutil/imgutils.h"
 25#include "libavutil/opt.h"
 26#include "avcodec.h"
 27#include "bytestream.h"
 28#include "internal.h"
 29#include "lzw.h"
 30#include "gif.h"
 31
 32/* This value is intentionally set to "transparent white" color.
 33 * It is much better to have white background instead of black
 34 * when gif image converted to format which not support transparency.
 35 */
 36#define GIF_TRANSPARENT_COLOR    0x00ffffff
 37
 38typedef struct GifState {
 39    const AVClass *class;
 40    AVFrame *frame;
 41    int screen_width;
 42    int screen_height;
 43    int has_global_palette;
 44    int bits_per_pixel;
 45    uint32_t bg_color;
 46    int background_color_index;
 47    int transparent_color_index;
 48    int color_resolution;
 49    /* intermediate buffer for storing color indices
 50     * obtained from lzw-encoded data stream */
 51    uint8_t *idx_line;
 52    int idx_line_size;
 53
 54    /* after the frame is displayed, the disposal method is used */
 55    int gce_prev_disposal;
 56    int gce_disposal;
 57    /* rectangle describing area that must be disposed */
 58    int gce_l, gce_t, gce_w, gce_h;
 59    /* depending on disposal method we store either part of the image
 60     * drawn on the canvas or background color that
 61     * should be used upon disposal */
 62    uint32_t * stored_img;
 63    int stored_img_size;
 64    int stored_bg_color;
 65
 66    GetByteContext gb;
 67    LZWState *lzw;
 68
 69    /* aux buffers */
 70    uint32_t global_palette[256];
 71    uint32_t local_palette[256];
 72
 73    AVCodecContext *avctx;
 74    int keyframe;
 75    int keyframe_ok;
 76    int trans_color;    /**< color value that is used instead of transparent color */
 77} GifState;
 78
 79static void gif_read_palette(GifState *s, uint32_t *pal, int nb)
 80{
 81    int i;
 82
 83    for (i = 0; i < nb; i++, pal++)
 84        *pal = (0xffu << 24) | bytestream2_get_be24u(&s->gb);
 85}
 86
 87static void gif_fill(AVFrame *picture, uint32_t color)
 88{
 89    uint32_t *p = (uint32_t *)picture->data[0];
 90    uint32_t *p_end = p + (picture->linesize[0] / sizeof(uint32_t)) * picture->height;
 91
 92    for (; p < p_end; p++)
 93        *p = color;
 94}
 95
 96static void gif_fill_rect(AVFrame *picture, uint32_t color, int l, int t, int w, int h)
 97{
 98    const int linesize = picture->linesize[0] / sizeof(uint32_t);
 99    const uint32_t *py = (uint32_t *)picture->data[0] + t * linesize;
100    const uint32_t *pr, *pb = py + h * linesize;
101    uint32_t *px;
102
103    for (; py < pb; py += linesize) {
104        px = (uint32_t *)py + l;
105        pr = px + w;
106
107        for (; px < pr; px++)
108            *px = color;
109    }
110}
111
112static void gif_copy_img_rect(const uint32_t *src, uint32_t *dst,
113                              int linesize, int l, int t, int w, int h)
114{
115    const int y_start = t * linesize;
116    const uint32_t *src_px,
117                   *src_py = src + y_start,
118                   *dst_py = dst + y_start;
119    const uint32_t *src_pb = src_py + h * linesize;
120    uint32_t *dst_px;
121
122    for (; src_py < src_pb; src_py += linesize, dst_py += linesize) {
123        src_px = src_py + l;
124        dst_px = (uint32_t *)dst_py + l;
125
126        memcpy(dst_px, src_px, w * sizeof(uint32_t));
127    }
128}
129
130static int gif_read_image(GifState *s, AVFrame *frame)
131{
132    int left, top, width, height, bits_per_pixel, code_size, flags, pw;
133    int is_interleaved, has_local_palette, y, pass, y1, linesize, pal_size, lzwed_len;
134    uint32_t *ptr, *pal, *px, *pr, *ptr1;
135    int ret;
136    uint8_t *idx;
137
138    /* At least 9 bytes of Image Descriptor. */
139    if (bytestream2_get_bytes_left(&s->gb) < 9)
140        return AVERROR_INVALIDDATA;
141
142    left   = bytestream2_get_le16u(&s->gb);
143    top    = bytestream2_get_le16u(&s->gb);
144    width  = bytestream2_get_le16u(&s->gb);
145    height = bytestream2_get_le16u(&s->gb);
146    flags  = bytestream2_get_byteu(&s->gb);
147    is_interleaved = flags & 0x40;
148    has_local_palette = flags & 0x80;
149    bits_per_pixel = (flags & 0x07) + 1;
150
151    ff_dlog(s->avctx, "image x=%d y=%d w=%d h=%d\n", left, top, width, height);
152
153    if (has_local_palette) {
154        pal_size = 1 << bits_per_pixel;
155
156        if (bytestream2_get_bytes_left(&s->gb) < pal_size * 3)
157            return AVERROR_INVALIDDATA;
158
159        gif_read_palette(s, s->local_palette, pal_size);
160        pal = s->local_palette;
161    } else {
162        if (!s->has_global_palette) {
163            av_log(s->avctx, AV_LOG_ERROR, "picture doesn't have either global or local palette.\n");
164            return AVERROR_INVALIDDATA;
165        }
166
167        pal = s->global_palette;
168    }
169
170    if (s->keyframe) {
171        if (s->transparent_color_index == -1 && s->has_global_palette) {
172            /* transparency wasn't set before the first frame, fill with background color */
173            gif_fill(frame, s->bg_color);
174        } else {
175            /* otherwise fill with transparent color.
176             * this is necessary since by default picture filled with 0x80808080. */
177            gif_fill(frame, s->trans_color);
178        }
179    }
180
181    /* verify that all the image is inside the screen dimensions */
182    if (!width || width > s->screen_width) {
183        av_log(s->avctx, AV_LOG_WARNING, "Invalid image width: %d, truncating.\n", width);
184        width = s->screen_width;
185    }
186    if (left >= s->screen_width) {
187        av_log(s->avctx, AV_LOG_ERROR, "Invalid left position: %d.\n", left);
188        return AVERROR_INVALIDDATA;
189    }
190    if (!height || height > s->screen_height) {
191        av_log(s->avctx, AV_LOG_WARNING, "Invalid image height: %d, truncating.\n", height);
192        height = s->screen_height;
193    }
194    if (top >= s->screen_height) {
195        av_log(s->avctx, AV_LOG_ERROR, "Invalid top position: %d.\n", top);
196        return AVERROR_INVALIDDATA;
197    }
198    if (left + width > s->screen_width) {
199        /* width must be kept around to avoid lzw vs line desync */
200        pw = s->screen_width - left;
201        av_log(s->avctx, AV_LOG_WARNING, "Image too wide by %d, truncating.\n",
202               left + width - s->screen_width);
203    } else {
204        pw = width;
205    }
206    if (top + height > s->screen_height) {
207        /* we don't care about the extra invisible lines */
208        av_log(s->avctx, AV_LOG_WARNING, "Image too high by %d, truncating.\n",
209               top + height - s->screen_height);
210        height = s->screen_height - top;
211    }
212
213    /* process disposal method */
214    if (s->gce_prev_disposal == GCE_DISPOSAL_BACKGROUND) {
215        gif_fill_rect(frame, s->stored_bg_color, s->gce_l, s->gce_t, s->gce_w, s->gce_h);
216    } else if (s->gce_prev_disposal == GCE_DISPOSAL_RESTORE) {
217        gif_copy_img_rect(s->stored_img, (uint32_t *)frame->data[0],
218            frame->linesize[0] / sizeof(uint32_t), s->gce_l, s->gce_t, s->gce_w, s->gce_h);
219    }
220
221    s->gce_prev_disposal = s->gce_disposal;
222
223    if (s->gce_disposal != GCE_DISPOSAL_NONE) {
224        s->gce_l = left;  s->gce_t = top;
225        s->gce_w = pw;    s->gce_h = height;
226
227        if (s->gce_disposal == GCE_DISPOSAL_BACKGROUND) {
228            if (s->transparent_color_index >= 0)
229                s->stored_bg_color = s->trans_color;
230            else
231                s->stored_bg_color = s->bg_color;
232        } else if (s->gce_disposal == GCE_DISPOSAL_RESTORE) {
233            av_fast_malloc(&s->stored_img, &s->stored_img_size, frame->linesize[0] * frame->height);
234            if (!s->stored_img)
235                return AVERROR(ENOMEM);
236
237            gif_copy_img_rect((uint32_t *)frame->data[0], s->stored_img,
238                frame->linesize[0] / sizeof(uint32_t), left, top, pw, height);
239        }
240    }
241
242    /* Expect at least 2 bytes: 1 for lzw code size and 1 for block size. */
243    if (bytestream2_get_bytes_left(&s->gb) < 2)
244        return AVERROR_INVALIDDATA;
245
246    /* now get the image data */
247    code_size = bytestream2_get_byteu(&s->gb);
248    if ((ret = ff_lzw_decode_init(s->lzw, code_size, s->gb.buffer,
249                                  bytestream2_get_bytes_left(&s->gb), FF_LZW_GIF)) < 0) {
250        av_log(s->avctx, AV_LOG_ERROR, "LZW init failed\n");
251        return ret;
252    }
253
254    /* read all the image */
255    linesize = frame->linesize[0] / sizeof(uint32_t);
256    ptr1 = (uint32_t *)frame->data[0] + top * linesize + left;
257    ptr = ptr1;
258    pass = 0;
259    y1 = 0;
260    for (y = 0; y < height; y++) {
261        int count = ff_lzw_decode(s->lzw, s->idx_line, width);
262        if (count != width) {
263            if (count)
264                av_log(s->avctx, AV_LOG_ERROR, "LZW decode failed\n");
265            goto decode_tail;
266        }
267
268        pr = ptr + pw;
269
270        for (px = ptr, idx = s->idx_line; px < pr; px++, idx++) {
271            if (*idx != s->transparent_color_index)
272                *px = pal[*idx];
273        }
274
275        if (is_interleaved) {
276            switch(pass) {
277            default:
278            case 0:
279            case 1:
280                y1 += 8;
281                ptr += linesize * 8;
282                break;
283            case 2:
284                y1 += 4;
285                ptr += linesize * 4;
286                break;
287            case 3:
288                y1 += 2;
289                ptr += linesize * 2;
290                break;
291            }
292            while (y1 >= height) {
293                y1  = 4 >> pass;
294                ptr = ptr1 + linesize * y1;
295                pass++;
296            }
297        } else {
298            ptr += linesize;
299        }
300    }
301
302 decode_tail:
303    /* read the garbage data until end marker is found */
304    lzwed_len = ff_lzw_decode_tail(s->lzw);
305    bytestream2_skipu(&s->gb, lzwed_len);
306
307    /* Graphic Control Extension's scope is single frame.
308     * Remove its influence. */
309    s->transparent_color_index = -1;
310    s->gce_disposal = GCE_DISPOSAL_NONE;
311
312    return 0;
313}
314
315static int gif_read_extension(GifState *s)
316{
317    int ext_code, ext_len, gce_flags, gce_transparent_index;
318
319    /* There must be at least 2 bytes:
320     * 1 for extension label and 1 for extension length. */
321    if (bytestream2_get_bytes_left(&s->gb) < 2)
322        return AVERROR_INVALIDDATA;
323
324    ext_code = bytestream2_get_byteu(&s->gb);
325    ext_len  = bytestream2_get_byteu(&s->gb);
326
327    ff_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);
328
329    switch(ext_code) {
330    case GIF_GCE_EXT_LABEL:
331        if (ext_len != 4)
332            goto discard_ext;
333
334        /* We need at least 5 bytes more: 4 is for extension body
335         * and 1 for next block size. */
336        if (bytestream2_get_bytes_left(&s->gb) < 5)
337            return AVERROR_INVALIDDATA;
338
339        gce_flags    = bytestream2_get_byteu(&s->gb);
340        bytestream2_skipu(&s->gb, 2);    // delay during which the frame is shown
341        gce_transparent_index = bytestream2_get_byteu(&s->gb);
342        if (gce_flags & 0x01)
343            s->transparent_color_index = gce_transparent_index;
344        else
345            s->transparent_color_index = -1;
346        s->gce_disposal = (gce_flags >> 2) & 0x7;
347
348        ff_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
349               gce_flags,
350               s->transparent_color_index, s->gce_disposal);
351
352        if (s->gce_disposal > 3) {
353            s->gce_disposal = GCE_DISPOSAL_NONE;
354            ff_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
355        }
356
357        ext_len = bytestream2_get_byteu(&s->gb);
358        break;
359    }
360
361    /* NOTE: many extension blocks can come after */
362 discard_ext:
363    while (ext_len) {
364        /* There must be at least ext_len bytes and 1 for next block size byte. */
365        if (bytestream2_get_bytes_left(&s->gb) < ext_len + 1)
366            return AVERROR_INVALIDDATA;
367
368        bytestream2_skipu(&s->gb, ext_len);
369        ext_len = bytestream2_get_byteu(&s->gb);
370
371        ff_dlog(s->avctx, "ext_len1=%d\n", ext_len);
372    }
373    return 0;
374}
375
376static int gif_read_header1(GifState *s)
377{
378    uint8_t sig[6];
379    int v, n;
380    int background_color_index;
381
382    if (bytestream2_get_bytes_left(&s->gb) < 13)
383        return AVERROR_INVALIDDATA;
384
385    /* read gif signature */
386    bytestream2_get_bufferu(&s->gb, sig, 6);
387    if (memcmp(sig, gif87a_sig, 6) &&
388        memcmp(sig, gif89a_sig, 6))
389        return AVERROR_INVALIDDATA;
390
391    /* read screen header */
392    s->transparent_color_index = -1;
393    s->screen_width  = bytestream2_get_le16u(&s->gb);
394    s->screen_height = bytestream2_get_le16u(&s->gb);
395
396    v = bytestream2_get_byteu(&s->gb);
397    s->color_resolution = ((v & 0x70) >> 4) + 1;
398    s->has_global_palette = (v & 0x80);
399    s->bits_per_pixel = (v & 0x07) + 1;
400    background_color_index = bytestream2_get_byteu(&s->gb);
401    n = bytestream2_get_byteu(&s->gb);
402    if (n) {
403        s->avctx->sample_aspect_ratio.num = n + 15;
404        s->avctx->sample_aspect_ratio.den = 64;
405    }
406
407    ff_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
408           s->screen_width, s->screen_height, s->bits_per_pixel,
409           s->has_global_palette);
410
411    if (s->has_global_palette) {
412        s->background_color_index = background_color_index;
413        n = 1 << s->bits_per_pixel;
414        if (bytestream2_get_bytes_left(&s->gb) < n * 3)
415            return AVERROR_INVALIDDATA;
416
417        gif_read_palette(s, s->global_palette, n);
418        s->bg_color = s->global_palette[s->background_color_index];
419    } else
420        s->background_color_index = -1;
421
422    return 0;
423}
424
425static int gif_parse_next_image(GifState *s, AVFrame *frame)
426{
427    while (bytestream2_get_bytes_left(&s->gb) > 0) {
428        int code = bytestream2_get_byte(&s->gb);
429        int ret;
430
431        av_log(s->avctx, AV_LOG_DEBUG, "code=%02x '%c'\n", code, code);
432
433        switch (code) {
434        case GIF_IMAGE_SEPARATOR:
435            return gif_read_image(s, frame);
436        case GIF_EXTENSION_INTRODUCER:
437            if ((ret = gif_read_extension(s)) < 0)
438                return ret;
439            break;
440        case GIF_TRAILER:
441            /* end of image */
442            return AVERROR_EOF;
443        default:
444            /* erroneous block label */
445            return AVERROR_INVALIDDATA;
446        }
447    }
448    return AVERROR_EOF;
449}
450
451static av_cold int gif_decode_init(AVCodecContext *avctx)
452{
453    GifState *s = avctx->priv_data;
454
455    s->avctx = avctx;
456
457    avctx->pix_fmt = AV_PIX_FMT_RGB32;
458    s->frame = av_frame_alloc();
459    if (!s->frame)
460        return AVERROR(ENOMEM);
461    ff_lzw_decode_open(&s->lzw);
462    if (!s->lzw)
463        return AVERROR(ENOMEM);
464    return 0;
465}
466
467static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
468{
469    GifState *s = avctx->priv_data;
470    int ret;
471
472    bytestream2_init(&s->gb, avpkt->data, avpkt->size);
473
474    s->frame->pts     = avpkt->pts;
475#if FF_API_PKT_PTS
476FF_DISABLE_DEPRECATION_WARNINGS
477    s->frame->pkt_pts = avpkt->pts;
478FF_ENABLE_DEPRECATION_WARNINGS
479#endif
480    s->frame->pkt_dts = avpkt->dts;
481    s->frame->pkt_duration = avpkt->duration;
482
483    if (avpkt->size >= 6) {
484        s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
485                      memcmp(avpkt->data, gif89a_sig, 6) == 0;
486    } else {
487        s->keyframe = 0;
488    }
489
490    if (s->keyframe) {
491        s->keyframe_ok = 0;
492        s->gce_prev_disposal = GCE_DISPOSAL_NONE;
493        if ((ret = gif_read_header1(s)) < 0)
494            return ret;
495
496        if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
497            return ret;
498
499        av_frame_unref(s->frame);
500        if ((ret = ff_get_buffer(avctx, s->frame, 0)) < 0)
501            return ret;
502
503        av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
504        if (!s->idx_line)
505            return AVERROR(ENOMEM);
506
507        s->frame->pict_type = AV_PICTURE_TYPE_I;
508        s->frame->key_frame = 1;
509        s->keyframe_ok = 1;
510    } else {
511        if (!s->keyframe_ok) {
512            av_log(avctx, AV_LOG_ERROR, "cannot decode frame without keyframe\n");
513            return AVERROR_INVALIDDATA;
514        }
515
516        if ((ret = ff_reget_buffer(avctx, s->frame, 0)) < 0)
517            return ret;
518
519        s->frame->pict_type = AV_PICTURE_TYPE_P;
520        s->frame->key_frame = 0;
521    }
522
523    ret = gif_parse_next_image(s, s->frame);
524    if (ret < 0)
525        return ret;
526
527    if ((ret = av_frame_ref(data, s->frame)) < 0)
528        return ret;
529    *got_frame = 1;
530
531    return bytestream2_tell(&s->gb);
532}
533
534static av_cold int gif_decode_close(AVCodecContext *avctx)
535{
536    GifState *s = avctx->priv_data;
537
538    ff_lzw_decode_close(&s->lzw);
539    av_frame_free(&s->frame);
540    av_freep(&s->idx_line);
541    av_freep(&s->stored_img);
542
543    return 0;
544}
545
546static const AVOption options[] = {
547    { "trans_color", "color value (ARGB) that is used instead of transparent color",
548      offsetof(GifState, trans_color), AV_OPT_TYPE_INT,
549      {.i64 = GIF_TRANSPARENT_COLOR}, 0, 0xffffffff,
550      AV_OPT_FLAG_DECODING_PARAM|AV_OPT_FLAG_VIDEO_PARAM },
551    { NULL },
552};
553
554static const AVClass decoder_class = {
555    .class_name = "gif decoder",
556    .item_name  = av_default_item_name,
557    .option     = options,
558    .version    = LIBAVUTIL_VERSION_INT,
559    .category   = AV_CLASS_CATEGORY_DECODER,
560};
561
562AVCodec ff_gif_decoder = {
563    .name           = "gif",
564    .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
565    .type           = AVMEDIA_TYPE_VIDEO,
566    .id             = AV_CODEC_ID_GIF,
567    .priv_data_size = sizeof(GifState),
568    .init           = gif_decode_init,
569    .close          = gif_decode_close,
570    .decode         = gif_decode_frame,
571    .capabilities   = AV_CODEC_CAP_DR1,
572    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE |
573                      FF_CODEC_CAP_INIT_CLEANUP,
574    .priv_class     = &decoder_class,
575};