PeerStreamer

/*

 * GIF encoder.

 * Copyright (c) 2000 Fabrice Bellard

 * Copyright (c) 2002 Francois Revol

 * 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

 */

/*

 * First version by Francois Revol revol@free.fr

 *

 * Features and limitations:

 * - currently no compression is performed,

 *   in fact the size of the data is 9/8 the size of the image in 8bpp

 * - uses only a global standard palette

 * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).

 *

 * Reference documents:

 * http://www.goice.co.jp/member/mo/formats/gif.html

 * http://astronomy.swin.edu.au/pbourke/dataformats/gif/

 * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt

 *

 * this url claims to have an LZW algorithm not covered by Unisys patent:

 * http://www.msg.net/utility/whirlgif/gifencod.html

 * could help reduce the size of the files _a lot_...

 * some sites mentions an RLE type compression also.

 */

#include "avcodec.h"

#include "bytestream.h"

#include "lzw.h"

/* The GIF format uses reversed order for bitstreams... */

/* at least they don't use PDP_ENDIAN :) */

#define BITSTREAM_WRITER_LE

#include "put_bits.h"

typedef struct {

    AVFrame picture;

    LZWState *lzw;

    uint8_t *buf;

} GIFContext;

/* GIF header */

static int gif_image_write_header(AVCodecContext *avctx,

                                  uint8_t **bytestream, uint32_t *palette)

{

    int i;

    unsigned int v;

    bytestream_put_buffer(bytestream, "GIF", 3);

    bytestream_put_buffer(bytestream, "89a", 3);

    bytestream_put_le16(bytestream, avctx->width);

    bytestream_put_le16(bytestream, avctx->height);

    bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */

    bytestream_put_byte(bytestream, 0x1f); /* background color index */

    bytestream_put_byte(bytestream, 0); /* aspect ratio */

    /* the global palette */

    for(i=0;i<256;i++) {

        v = palette[i];

        bytestream_put_be24(bytestream, v);

    }

    return 0;

}

static int gif_image_write_image(AVCodecContext *avctx,

                                 uint8_t **bytestream, uint8_t *end,

                                 const uint8_t *buf, int linesize)

{

    GIFContext *s = avctx->priv_data;

    int len, height;

    const uint8_t *ptr;

    /* image block */

    bytestream_put_byte(bytestream, 0x2c);

    bytestream_put_le16(bytestream, 0);

    bytestream_put_le16(bytestream, 0);

    bytestream_put_le16(bytestream, avctx->width);

    bytestream_put_le16(bytestream, avctx->height);

    bytestream_put_byte(bytestream, 0x00); /* flags */

    /* no local clut */

    bytestream_put_byte(bytestream, 0x08);

    ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,

                       12, FF_LZW_GIF, put_bits);

    ptr = buf;

    for (height = avctx->height; height--;) {

        len += ff_lzw_encode(s->lzw, ptr, avctx->width);

        ptr += linesize;

    }

    len += ff_lzw_encode_flush(s->lzw, flush_put_bits);

    ptr = s->buf;

    while (len > 0) {

        int size = FFMIN(255, len);

        bytestream_put_byte(bytestream, size);

        if (end - *bytestream < size)

            return -1;

        bytestream_put_buffer(bytestream, ptr, size);

        ptr += size;

        len -= size;

    }

    bytestream_put_byte(bytestream, 0x00); /* end of image block */

    bytestream_put_byte(bytestream, 0x3b);

    return 0;

}

static av_cold int gif_encode_init(AVCodecContext *avctx)

{

    GIFContext *s = avctx->priv_data;

    avctx->coded_frame = &s->picture;

    s->lzw = av_mallocz(ff_lzw_encode_state_size);

    if (!s->lzw)

        return AVERROR(ENOMEM);

    s->buf = av_malloc(avctx->width*avctx->height*2);

    if (!s->buf)

         return AVERROR(ENOMEM);

    return 0;

}

/* better than nothing gif encoder */

static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)

{

    GIFContext *s = avctx->priv_data;

    AVFrame *pict = data;

    AVFrame *const p = (AVFrame *)&s->picture;

    uint8_t *outbuf_ptr = outbuf;

    uint8_t *end = outbuf + buf_size;

    *p = *pict;

    p->pict_type = FF_I_TYPE;

    p->key_frame = 1;

    gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);

    gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);

    return outbuf_ptr - outbuf;

}

static int gif_encode_close(AVCodecContext *avctx)

{

    GIFContext *s = avctx->priv_data;

    av_freep(&s->lzw);

    av_freep(&s->buf);

    return 0;

}

AVCodec gif_encoder = {

    "gif",

    AVMEDIA_TYPE_VIDEO,

    CODEC_ID_GIF,

    sizeof(GIFContext),

    gif_encode_init,

    gif_encode_frame,

    gif_encode_close,

    .pix_fmts= (const enum PixelFormat[]){PIX_FMT_RGB8, PIX_FMT_BGR8, PIX_FMT_RGB4_BYTE, PIX_FMT_BGR4_BYTE, PIX_FMT_GRAY8, PIX_FMT_PAL8, PIX_FMT_NONE},

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

};