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ffmpeg / libavcodec / gifdec.c @ 73a0b19b

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/*
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 * GIF decoder
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 * Copyright (c) 2003 Fabrice Bellard
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 * Copyright (c) 2006 Baptiste Coudurier
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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//#define DEBUG
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#include "libavcore/imgutils.h"
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#include "avcodec.h"
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#include "bytestream.h"
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#include "lzw.h"
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#define GCE_DISPOSAL_NONE       0
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#define GCE_DISPOSAL_INPLACE    1
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#define GCE_DISPOSAL_BACKGROUND 2
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#define GCE_DISPOSAL_RESTORE    3
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typedef struct GifState {
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    AVFrame picture;
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    int screen_width;
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    int screen_height;
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    int bits_per_pixel;
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    int background_color_index;
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    int transparent_color_index;
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    int color_resolution;
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    uint32_t *image_palette;
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    /* after the frame is displayed, the disposal method is used */
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    int gce_disposal;
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    /* delay during which the frame is shown */
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    int gce_delay;
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    /* LZW compatible decoder */
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    const uint8_t *bytestream;
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    const uint8_t *bytestream_end;
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    LZWState *lzw;
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    /* aux buffers */
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    uint8_t global_palette[256 * 3];
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    uint8_t local_palette[256 * 3];
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  AVCodecContext* avctx;
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} GifState;
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static const uint8_t gif87a_sig[6] = "GIF87a";
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static const uint8_t gif89a_sig[6] = "GIF89a";
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static int gif_read_image(GifState *s)
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{
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    int left, top, width, height, bits_per_pixel, code_size, flags;
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    int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
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    uint8_t *ptr, *spal, *palette, *ptr1;
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    left = bytestream_get_le16(&s->bytestream);
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    top = bytestream_get_le16(&s->bytestream);
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    width = bytestream_get_le16(&s->bytestream);
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    height = bytestream_get_le16(&s->bytestream);
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    flags = bytestream_get_byte(&s->bytestream);
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    is_interleaved = flags & 0x40;
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    has_local_palette = flags & 0x80;
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    bits_per_pixel = (flags & 0x07) + 1;
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    dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
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    if (has_local_palette) {
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        bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
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        palette = s->local_palette;
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    } else {
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        palette = s->global_palette;
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        bits_per_pixel = s->bits_per_pixel;
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    }
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    /* verify that all the image is inside the screen dimensions */
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    if (left + width > s->screen_width ||
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        top + height > s->screen_height)
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        return AVERROR(EINVAL);
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    /* build the palette */
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    n = (1 << bits_per_pixel);
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    spal = palette;
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    for(i = 0; i < n; i++) {
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        s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
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        spal += 3;
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    }
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    for(; i < 256; i++)
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        s->image_palette[i] = (0xff << 24);
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    /* handle transparency */
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    if (s->transparent_color_index >= 0)
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        s->image_palette[s->transparent_color_index] = 0;
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    /* now get the image data */
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    code_size = bytestream_get_byte(&s->bytestream);
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    ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
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                       s->bytestream_end - s->bytestream, FF_LZW_GIF);
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    /* read all the image */
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    linesize = s->picture.linesize[0];
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    ptr1 = s->picture.data[0] + top * linesize + left;
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    ptr = ptr1;
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    pass = 0;
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    y1 = 0;
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    for (y = 0; y < height; y++) {
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        ff_lzw_decode(s->lzw, ptr, width);
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        if (is_interleaved) {
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            switch(pass) {
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            default:
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            case 0:
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            case 1:
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                y1 += 8;
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                ptr += linesize * 8;
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                if (y1 >= height) {
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                    y1 = pass ? 2 : 4;
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                    ptr = ptr1 + linesize * y1;
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                    pass++;
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                }
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                break;
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            case 2:
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                y1 += 4;
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                ptr += linesize * 4;
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                if (y1 >= height) {
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                    y1 = 1;
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                    ptr = ptr1 + linesize;
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                    pass++;
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                }
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                break;
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            case 3:
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                y1 += 2;
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                ptr += linesize * 2;
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                break;
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            }
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        } else {
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            ptr += linesize;
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        }
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    }
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    /* read the garbage data until end marker is found */
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    ff_lzw_decode_tail(s->lzw);
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    s->bytestream = ff_lzw_cur_ptr(s->lzw);
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    return 0;
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}
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static int gif_read_extension(GifState *s)
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{
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    int ext_code, ext_len, i, gce_flags, gce_transparent_index;
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    /* extension */
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    ext_code = bytestream_get_byte(&s->bytestream);
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    ext_len = bytestream_get_byte(&s->bytestream);
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    dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
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    switch(ext_code) {
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    case 0xf9:
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        if (ext_len != 4)
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            goto discard_ext;
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        s->transparent_color_index = -1;
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        gce_flags = bytestream_get_byte(&s->bytestream);
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        s->gce_delay = bytestream_get_le16(&s->bytestream);
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        gce_transparent_index = bytestream_get_byte(&s->bytestream);
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        if (gce_flags & 0x01)
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            s->transparent_color_index = gce_transparent_index;
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        else
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            s->transparent_color_index = -1;
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        s->gce_disposal = (gce_flags >> 2) & 0x7;
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        dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
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               gce_flags, s->gce_delay,
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               s->transparent_color_index, s->gce_disposal);
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        ext_len = bytestream_get_byte(&s->bytestream);
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        break;
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    }
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    /* NOTE: many extension blocks can come after */
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 discard_ext:
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    while (ext_len != 0) {
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        for (i = 0; i < ext_len; i++)
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            bytestream_get_byte(&s->bytestream);
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        ext_len = bytestream_get_byte(&s->bytestream);
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        dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
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    }
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    return 0;
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}
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static int gif_read_header1(GifState *s)
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{
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    uint8_t sig[6];
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    int v, n;
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    int has_global_palette;
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    if (s->bytestream_end < s->bytestream + 13)
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        return -1;
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    /* read gif signature */
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    bytestream_get_buffer(&s->bytestream, sig, 6);
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    if (memcmp(sig, gif87a_sig, 6) != 0 &&
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        memcmp(sig, gif89a_sig, 6) != 0)
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        return -1;
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    /* read screen header */
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    s->transparent_color_index = -1;
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    s->screen_width = bytestream_get_le16(&s->bytestream);
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    s->screen_height = bytestream_get_le16(&s->bytestream);
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    if(   (unsigned)s->screen_width  > 32767
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       || (unsigned)s->screen_height > 32767){
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        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
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        return -1;
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    }
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    v = bytestream_get_byte(&s->bytestream);
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    s->color_resolution = ((v & 0x70) >> 4) + 1;
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    has_global_palette = (v & 0x80);
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    s->bits_per_pixel = (v & 0x07) + 1;
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    s->background_color_index = bytestream_get_byte(&s->bytestream);
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    bytestream_get_byte(&s->bytestream);                /* ignored */
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    dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
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           s->screen_width, s->screen_height, s->bits_per_pixel,
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           has_global_palette);
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    if (has_global_palette) {
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        n = 1 << s->bits_per_pixel;
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        if (s->bytestream_end < s->bytestream + n * 3)
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            return -1;
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        bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
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    }
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    return 0;
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}
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static int gif_parse_next_image(GifState *s)
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{
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    while (s->bytestream < s->bytestream_end) {
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        int code = bytestream_get_byte(&s->bytestream);
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        dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
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        switch (code) {
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        case ',':
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            return gif_read_image(s);
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        case '!':
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            if (gif_read_extension(s) < 0)
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                return -1;
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            break;
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        case ';':
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            /* end of image */
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        default:
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            /* error or erroneous EOF */
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            return -1;
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        }
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    }
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    return -1;
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}
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static av_cold int gif_decode_init(AVCodecContext *avctx)
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{
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    GifState *s = avctx->priv_data;
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    s->avctx = avctx;
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    avcodec_get_frame_defaults(&s->picture);
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    avctx->coded_frame= &s->picture;
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    s->picture.data[0] = NULL;
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    ff_lzw_decode_open(&s->lzw);
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    return 0;
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}
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static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
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{
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    const uint8_t *buf = avpkt->data;
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    int buf_size = avpkt->size;
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    GifState *s = avctx->priv_data;
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    AVFrame *picture = data;
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    int ret;
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    s->bytestream = buf;
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    s->bytestream_end = buf + buf_size;
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    if (gif_read_header1(s) < 0)
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        return -1;
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    avctx->pix_fmt = PIX_FMT_PAL8;
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    if (av_image_check_size(s->screen_width, s->screen_height, 0, avctx))
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        return -1;
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    avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
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    if (s->picture.data[0])
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        avctx->release_buffer(avctx, &s->picture);
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    if (avctx->get_buffer(avctx, &s->picture) < 0) {
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        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
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        return -1;
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    }
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    s->image_palette = (uint32_t *)s->picture.data[1];
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    ret = gif_parse_next_image(s);
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    if (ret < 0)
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        return ret;
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    *picture = s->picture;
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    *data_size = sizeof(AVPicture);
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    return s->bytestream - buf;
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}
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static av_cold int gif_decode_close(AVCodecContext *avctx)
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{
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    GifState *s = avctx->priv_data;
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    ff_lzw_decode_close(&s->lzw);
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    if(s->picture.data[0])
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        avctx->release_buffer(avctx, &s->picture);
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    return 0;
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}
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AVCodec gif_decoder = {
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    "gif",
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    AVMEDIA_TYPE_VIDEO,
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    CODEC_ID_GIF,
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    sizeof(GifState),
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    gif_decode_init,
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    NULL,
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    gif_decode_close,
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    gif_decode_frame,
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    CODEC_CAP_DR1,
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    .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
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};