3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2002 Francois Revol
5 * Copyright (c) 2006 Baptiste Coudurier
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 * First version by Francois Revol revol@free.fr
27 * Features and limitations:
28 * - currently no compression is performed,
29 * in fact the size of the data is 9/8 the size of the image in 8bpp
30 * - uses only a global standard palette
31 * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
33 * Reference documents:
34 * http://www.goice.co.jp/member/mo/formats/gif.html
35 * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
36 * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
38 * this url claims to have an LZW algorithm not covered by Unisys patent:
39 * http://www.msg.net/utility/whirlgif/gifencod.html
40 * could help reduce the size of the files _a lot_...
41 * some sites mentions an RLE type compression also.
45 #include "bytestream.h"
47 /* The GIF format uses reversed order for bitstreams... */
48 /* at least they don't use PDP_ENDIAN :) */
49 #define BITSTREAM_WRITER_LE
53 /* bitstream minipacket size */
54 #define GIF_CHUNKS 100
61 static int gif_image_write_header(uint8_t **bytestream,
62 int width, int height,
68 bytestream_put_buffer(bytestream, "GIF", 3);
69 bytestream_put_buffer(bytestream, "89a", 3);
70 bytestream_put_le16(bytestream, width);
71 bytestream_put_le16(bytestream, height);
73 bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
74 bytestream_put_byte(bytestream, 0x1f); /* background color index */
75 bytestream_put_byte(bytestream, 0); /* aspect ratio */
77 /* the global palette */
80 bytestream_put_be24(bytestream, v);
86 static int gif_image_write_image(uint8_t **bytestream,
87 int width, int height,
88 const uint8_t *buf, int linesize, int pix_fmt)
91 uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
96 bytestream_put_byte(bytestream, 0x2c);
97 bytestream_put_le16(bytestream, 0);
98 bytestream_put_le16(bytestream, 0);
99 bytestream_put_le16(bytestream, width);
100 bytestream_put_le16(bytestream, height);
101 bytestream_put_byte(bytestream, 0x00); /* flags */
104 bytestream_put_byte(bytestream, 0x08);
106 left= width * height;
108 init_put_bits(&p, buffer, 130);
111 * the thing here is the bitstream is written as little packets, with a size byte before
112 * but it's still the same bitstream between packets (no flush !)
118 put_bits(&p, 9, 0x0100); /* clear code */
120 for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
121 put_bits(&p, 9, *ptr++);
129 if(left<=GIF_CHUNKS) {
130 put_bits(&p, 9, 0x101); /* end of stream */
133 if(put_bits_ptr(&p) - p.buf > 0) {
134 bytestream_put_byte(bytestream, put_bits_ptr(&p) - p.buf); /* byte count of the packet */
135 bytestream_put_buffer(bytestream, p.buf, put_bits_ptr(&p) - p.buf); /* the actual buffer */
136 p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
140 bytestream_put_byte(bytestream, 0x00); /* end of image block */
141 bytestream_put_byte(bytestream, 0x3b);
145 static av_cold int gif_encode_init(AVCodecContext *avctx)
147 GIFContext *s = avctx->priv_data;
149 avctx->coded_frame = &s->picture;
153 /* better than nothing gif encoder */
154 static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)
156 GIFContext *s = avctx->priv_data;
157 AVFrame *pict = data;
158 AVFrame *const p = (AVFrame *)&s->picture;
159 uint8_t *outbuf_ptr = outbuf;
162 p->pict_type = FF_I_TYPE;
164 gif_image_write_header(&outbuf_ptr, avctx->width, avctx->height, (uint32_t *)pict->data[1]);
165 gif_image_write_image(&outbuf_ptr, avctx->width, avctx->height, pict->data[0], pict->linesize[0], PIX_FMT_PAL8);
166 return outbuf_ptr - outbuf;
169 AVCodec gif_encoder = {
177 .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},
178 .long_name= NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),