ffmpeg / libavcodec / gif.c @ 2874c81c
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/*
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* GIF encoder.
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* Copyright (c) 2000 Fabrice Bellard
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* Copyright (c) 2002 Francois Revol
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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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/*
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* First version by Francois Revol revol@free.fr
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*
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* Features and limitations:
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* - currently no compression is performed,
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* in fact the size of the data is 9/8 the size of the image in 8bpp
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* - uses only a global standard palette
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* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
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*
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* Reference documents:
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* http://www.goice.co.jp/member/mo/formats/gif.html
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* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
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* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
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*
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* this url claims to have an LZW algorithm not covered by Unisys patent:
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* http://www.msg.net/utility/whirlgif/gifencod.html
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* could help reduce the size of the files _a lot_...
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* some sites mentions an RLE type compression also.
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*/
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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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/* The GIF format uses reversed order for bitstreams... */
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/* at least they don't use PDP_ENDIAN :) */
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#define BITSTREAM_WRITER_LE
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#include "put_bits.h" |
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typedef struct { |
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AVFrame picture; |
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LZWState *lzw; |
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uint8_t *buf; |
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} GIFContext; |
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/* GIF header */
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static int gif_image_write_header(AVCodecContext *avctx, |
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uint8_t **bytestream, uint32_t *palette) |
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{ |
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int i;
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unsigned int v; |
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bytestream_put_buffer(bytestream, "GIF", 3); |
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bytestream_put_buffer(bytestream, "89a", 3); |
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bytestream_put_le16(bytestream, avctx->width); |
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bytestream_put_le16(bytestream, avctx->height); |
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bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */ |
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bytestream_put_byte(bytestream, 0x1f); /* background color index */ |
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bytestream_put_byte(bytestream, 0); /* aspect ratio */ |
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/* the global palette */
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for(i=0;i<256;i++) { |
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v = palette[i]; |
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bytestream_put_be24(bytestream, v); |
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} |
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return 0; |
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} |
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static int gif_image_write_image(AVCodecContext *avctx, |
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uint8_t **bytestream, uint8_t *end, |
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const uint8_t *buf, int linesize) |
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{ |
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GIFContext *s = avctx->priv_data; |
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int len, height;
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const uint8_t *ptr;
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/* image block */
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bytestream_put_byte(bytestream, 0x2c);
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bytestream_put_le16(bytestream, 0);
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bytestream_put_le16(bytestream, 0);
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bytestream_put_le16(bytestream, avctx->width); |
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bytestream_put_le16(bytestream, avctx->height); |
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bytestream_put_byte(bytestream, 0x00); /* flags */ |
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/* no local clut */
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bytestream_put_byte(bytestream, 0x08);
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ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height, |
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12, FF_LZW_GIF, put_bits);
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ptr = buf; |
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for (height = avctx->height; height--;) {
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len += ff_lzw_encode(s->lzw, ptr, avctx->width); |
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ptr += linesize; |
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} |
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len += ff_lzw_encode_flush(s->lzw, flush_put_bits); |
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ptr = s->buf; |
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while (len > 0) { |
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int size = FFMIN(255, len); |
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bytestream_put_byte(bytestream, size); |
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if (end - *bytestream < size)
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return -1; |
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bytestream_put_buffer(bytestream, ptr, size); |
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ptr += size; |
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len -= size; |
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} |
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bytestream_put_byte(bytestream, 0x00); /* end of image block */ |
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bytestream_put_byte(bytestream, 0x3b);
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return 0; |
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} |
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static av_cold int gif_encode_init(AVCodecContext *avctx) |
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{ |
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GIFContext *s = avctx->priv_data; |
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avctx->coded_frame = &s->picture; |
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s->lzw = av_mallocz(ff_lzw_encode_state_size); |
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if (!s->lzw)
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return AVERROR(ENOMEM);
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s->buf = av_malloc(avctx->width*avctx->height*2);
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if (!s->buf)
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return AVERROR(ENOMEM);
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return 0; |
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} |
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/* better than nothing gif encoder */
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static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data) |
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{ |
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GIFContext *s = avctx->priv_data; |
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AVFrame *pict = data; |
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AVFrame *const p = (AVFrame *)&s->picture;
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uint8_t *outbuf_ptr = outbuf; |
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uint8_t *end = outbuf + buf_size; |
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*p = *pict; |
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p->pict_type = FF_I_TYPE; |
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p->key_frame = 1;
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gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
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gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]); |
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return outbuf_ptr - outbuf;
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} |
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static int gif_encode_close(AVCodecContext *avctx) |
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{ |
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GIFContext *s = avctx->priv_data; |
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av_freep(&s->lzw); |
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av_freep(&s->buf); |
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return 0; |
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} |
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AVCodec gif_encoder = { |
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"gif",
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AVMEDIA_TYPE_VIDEO, |
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CODEC_ID_GIF, |
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sizeof(GIFContext),
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gif_encode_init, |
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gif_encode_frame, |
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gif_encode_close, |
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.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}, |
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.long_name= NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
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}; |