PeerStreamer

/*

 * GIF decoder

 * Copyright (c) 2003 Fabrice Bellard

 * Copyright (c) 2006 Baptiste Coudurier

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

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

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

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

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

 * Lesser General Public License for more details.

 *

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

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

//#define DEBUG

#include "libavcore/imgutils.h"

#include "avcodec.h"

#include "bytestream.h"

#include "lzw.h"

#define GCE_DISPOSAL_NONE       0

#define GCE_DISPOSAL_INPLACE    1

#define GCE_DISPOSAL_BACKGROUND 2

#define GCE_DISPOSAL_RESTORE    3

typedef struct GifState {

    AVFrame picture;

    int screen_width;

    int screen_height;

    int bits_per_pixel;

    int background_color_index;

    int transparent_color_index;

    int color_resolution;

    uint32_t *image_palette;

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

    int gce_disposal;

    /* delay during which the frame is shown */

    int gce_delay;

    /* LZW compatible decoder */

    const uint8_t *bytestream;

    const uint8_t *bytestream_end;

    LZWState *lzw;

    /* aux buffers */

    uint8_t global_palette[256 * 3];

    uint8_t local_palette[256 * 3];

  AVCodecContext* avctx;

} GifState;

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

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

static int gif_read_image(GifState *s)

{

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

    int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;

    uint8_t *ptr, *spal, *palette, *ptr1;

    left = bytestream_get_le16(&s->bytestream);

    top = bytestream_get_le16(&s->bytestream);

    width = bytestream_get_le16(&s->bytestream);

    height = bytestream_get_le16(&s->bytestream);

    flags = bytestream_get_byte(&s->bytestream);

    is_interleaved = flags & 0x40;

    has_local_palette = flags & 0x80;

    bits_per_pixel = (flags & 0x07) + 1;

    dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);

    if (has_local_palette) {

        bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));

        palette = s->local_palette;

    } else {

        palette = s->global_palette;

        bits_per_pixel = s->bits_per_pixel;

    }

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

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

        top + height > s->screen_height)

        return AVERROR(EINVAL);

    /* build the palette */

    n = (1 << bits_per_pixel);

    spal = palette;

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

        s->image_palette[i] = (0xff << 24) | AV_RB24(spal);

        spal += 3;

    }

    for(; i < 256; i++)

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

    /* handle transparency */

    if (s->transparent_color_index >= 0)

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

    /* now get the image data */

    code_size = bytestream_get_byte(&s->bytestream);

    ff_lzw_decode_init(s->lzw, code_size, s->bytestream,

                       s->bytestream_end - s->bytestream, FF_LZW_GIF);

    /* read all the image */

    linesize = s->picture.linesize[0];

    ptr1 = s->picture.data[0] + top * linesize + left;

    ptr = ptr1;

    pass = 0;

    y1 = 0;

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

        ff_lzw_decode(s->lzw, ptr, width);

        if (is_interleaved) {

            switch(pass) {

            default:

            case 0:

            case 1:

                y1 += 8;

                ptr += linesize * 8;

                if (y1 >= height) {

                    y1 = pass ? 2 : 4;

                    ptr = ptr1 + linesize * y1;

                    pass++;

                }

                break;

            case 2:

                y1 += 4;

                ptr += linesize * 4;

                if (y1 >= height) {

                    y1 = 1;

                    ptr = ptr1 + linesize;

                    pass++;

                }

                break;

            case 3:

                y1 += 2;

                ptr += linesize * 2;

                break;

            }

        } else {

            ptr += linesize;

        }

    }

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

    ff_lzw_decode_tail(s->lzw);

    s->bytestream = ff_lzw_cur_ptr(s->lzw);

    return 0;

}

static int gif_read_extension(GifState *s)

{

    int ext_code, ext_len, i, gce_flags, gce_transparent_index;

    /* extension */

    ext_code = bytestream_get_byte(&s->bytestream);

    ext_len = bytestream_get_byte(&s->bytestream);

    dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);

    switch(ext_code) {

    case 0xf9:

        if (ext_len != 4)

            goto discard_ext;

        s->transparent_color_index = -1;

        gce_flags = bytestream_get_byte(&s->bytestream);

        s->gce_delay = bytestream_get_le16(&s->bytestream);

        gce_transparent_index = bytestream_get_byte(&s->bytestream);

        if (gce_flags & 0x01)

            s->transparent_color_index = gce_transparent_index;

        else

            s->transparent_color_index = -1;

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

        dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",

               gce_flags, s->gce_delay,

               s->transparent_color_index, s->gce_disposal);

        ext_len = bytestream_get_byte(&s->bytestream);

        break;

    }

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

 discard_ext:

    while (ext_len != 0) {

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

            bytestream_get_byte(&s->bytestream);

        ext_len = bytestream_get_byte(&s->bytestream);

        dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);

    }

    return 0;

}

static int gif_read_header1(GifState *s)

{

    uint8_t sig[6];

    int v, n;

    int has_global_palette;

    if (s->bytestream_end < s->bytestream + 13)

        return -1;

    /* read gif signature */

    bytestream_get_buffer(&s->bytestream, sig, 6);

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

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

        return -1;

    /* read screen header */

    s->transparent_color_index = -1;

    s->screen_width = bytestream_get_le16(&s->bytestream);

    s->screen_height = bytestream_get_le16(&s->bytestream);

    if(   (unsigned)s->screen_width  > 32767

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

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

        return -1;

    }

    v = bytestream_get_byte(&s->bytestream);

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

    has_global_palette = (v & 0x80);

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

    s->background_color_index = bytestream_get_byte(&s->bytestream);

    bytestream_get_byte(&s->bytestream);                /* ignored */

    dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",

           s->screen_width, s->screen_height, s->bits_per_pixel,

           has_global_palette);

    if (has_global_palette) {

        n = 1 << s->bits_per_pixel;

        if (s->bytestream_end < s->bytestream + n * 3)

            return -1;

        bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);

    }

    return 0;

}

static int gif_parse_next_image(GifState *s)

{

    while (s->bytestream < s->bytestream_end) {

        int code = bytestream_get_byte(&s->bytestream);

        dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);

        switch (code) {

        case ',':

            return gif_read_image(s);

        case '!':

            if (gif_read_extension(s) < 0)

                return -1;

            break;

        case ';':

            /* end of image */

        default:

            /* error or erroneous EOF */

            return -1;

        }

    }

    return -1;

}

static av_cold int gif_decode_init(AVCodecContext *avctx)

{

    GifState *s = avctx->priv_data;

    s->avctx = avctx;

    avcodec_get_frame_defaults(&s->picture);

    avctx->coded_frame= &s->picture;

    s->picture.data[0] = NULL;

    ff_lzw_decode_open(&s->lzw);

    return 0;

}

static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size = avpkt->size;

    GifState *s = avctx->priv_data;

    AVFrame *picture = data;

    int ret;

    s->bytestream = buf;

    s->bytestream_end = buf + buf_size;

    if (gif_read_header1(s) < 0)

        return -1;

    avctx->pix_fmt = PIX_FMT_PAL8;

    if (av_image_check_size(s->screen_width, s->screen_height, 0, avctx))

        return -1;

    avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);

    if (s->picture.data[0])

        avctx->release_buffer(avctx, &s->picture);

    if (avctx->get_buffer(avctx, &s->picture) < 0) {

        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");

        return -1;

    }

    s->image_palette = (uint32_t *)s->picture.data[1];

    ret = gif_parse_next_image(s);

    if (ret < 0)

        return ret;

    *picture = s->picture;

    *data_size = sizeof(AVPicture);

    return s->bytestream - buf;

}

static av_cold int gif_decode_close(AVCodecContext *avctx)

{

    GifState *s = avctx->priv_data;

    ff_lzw_decode_close(&s->lzw);

    if(s->picture.data[0])

        avctx->release_buffer(avctx, &s->picture);

    return 0;

}

AVCodec ff_gif_decoder = {

    "gif",

    AVMEDIA_TYPE_VIDEO,

    CODEC_ID_GIF,

    sizeof(GifState),

    gif_decode_init,

    NULL,

    gif_decode_close,

    gif_decode_frame,

    CODEC_CAP_DR1,

    .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),

};