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/*
* 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 "internal.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, smallest_alpha = 0xFF, alpha_component = 0;
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);
if (v >> 24 < smallest_alpha) {
smallest_alpha = v >> 24;
alpha_component = i;
}
}
if (smallest_alpha < 128) {
bytestream_put_byte(bytestream, 0x21); /* Extension Introducer */
bytestream_put_byte(bytestream, 0xf9); /* Graphic Control Label */
bytestream_put_byte(bytestream, 0x04); /* block length */
bytestream_put_byte(bytestream, 0x01); /* Transparent Color Flag */
bytestream_put_le16(bytestream, 0x00); /* no delay */
bytestream_put_byte(bytestream, alpha_component);
bytestream_put_byte(bytestream, 0x00);
}
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 = 0, 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, AVPacket *pkt,
const AVFrame *pict, int *got_packet)
{
GIFContext *s = avctx->priv_data;
AVFrame *const p = &s->picture;
uint8_t *outbuf_ptr, *end;
int ret;
if ((ret = ff_alloc_packet2(avctx, pkt, avctx->width*avctx->height*7/5 + FF_MIN_BUFFER_SIZE)) < 0)
return ret;
outbuf_ptr = pkt->data;
end = pkt->data + pkt->size;
*p = *pict;
p->pict_type = AV_PICTURE_TYPE_I;
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]);
pkt->size = outbuf_ptr - pkt->data;
pkt->flags |= AV_PKT_FLAG_KEY;
*got_packet = 1;
return 0;
}
static int gif_encode_close(AVCodecContext *avctx)
{
GIFContext *s = avctx->priv_data;
av_freep(&s->lzw);
av_freep(&s->buf);
return 0;
}
AVCodec ff_gif_encoder = {
.name = "gif",
.type = AVMEDIA_TYPE_VIDEO,
.id = CODEC_ID_GIF,
.priv_data_size = sizeof(GIFContext),
.init = gif_encode_init,
.encode2 = gif_encode_frame,
.close = 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)"),
};
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