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"
49 /* The GIF format uses reversed order for bitstreams... */
50 /* at least they don't use PDP_ENDIAN :) */
51 #define BITSTREAM_WRITER_LE
62 static int gif_image_write_header(AVCodecContext *avctx,
63 uint8_t **bytestream, uint32_t *palette)
66 unsigned int v, smallest_alpha = 0xFF, alpha_component = 0;
68 bytestream_put_buffer(bytestream, "GIF", 3);
69 bytestream_put_buffer(bytestream, "89a", 3);
70 bytestream_put_le16(bytestream, avctx->width);
71 bytestream_put_le16(bytestream, avctx->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);
81 if (v >> 24 < smallest_alpha) {
82 smallest_alpha = v >> 24;
87 if (smallest_alpha < 128) {
88 bytestream_put_byte(bytestream, 0x21); /* Extension Introducer */
89 bytestream_put_byte(bytestream, 0xf9); /* Graphic Control Label */
90 bytestream_put_byte(bytestream, 0x04); /* block length */
91 bytestream_put_byte(bytestream, 0x01); /* Transparent Color Flag */
92 bytestream_put_le16(bytestream, 0x00); /* no delay */
93 bytestream_put_byte(bytestream, alpha_component);
94 bytestream_put_byte(bytestream, 0x00);
100 static int gif_image_write_image(AVCodecContext *avctx,
101 uint8_t **bytestream, uint8_t *end,
102 const uint8_t *buf, int linesize)
104 GIFContext *s = avctx->priv_data;
109 bytestream_put_byte(bytestream, 0x2c);
110 bytestream_put_le16(bytestream, 0);
111 bytestream_put_le16(bytestream, 0);
112 bytestream_put_le16(bytestream, avctx->width);
113 bytestream_put_le16(bytestream, avctx->height);
114 bytestream_put_byte(bytestream, 0x00); /* flags */
117 bytestream_put_byte(bytestream, 0x08);
119 ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,
120 12, FF_LZW_GIF, put_bits);
123 for (height = avctx->height; height--;) {
124 len += ff_lzw_encode(s->lzw, ptr, avctx->width);
127 len += ff_lzw_encode_flush(s->lzw, flush_put_bits);
131 int size = FFMIN(255, len);
132 bytestream_put_byte(bytestream, size);
133 if (end - *bytestream < size)
135 bytestream_put_buffer(bytestream, ptr, size);
139 bytestream_put_byte(bytestream, 0x00); /* end of image block */
140 bytestream_put_byte(bytestream, 0x3b);
144 static av_cold int gif_encode_init(AVCodecContext *avctx)
146 GIFContext *s = avctx->priv_data;
148 if (avctx->width > 65535 || avctx->height > 65535) {
149 av_log(avctx, AV_LOG_ERROR, "GIF does not support resolutions above 65535x65535\n");
153 avctx->coded_frame = &s->picture;
154 s->lzw = av_mallocz(ff_lzw_encode_state_size);
156 return AVERROR(ENOMEM);
157 s->buf = av_malloc(avctx->width*avctx->height*2);
159 return AVERROR(ENOMEM);
163 /* better than nothing gif encoder */
164 static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
165 const AVFrame *pict, int *got_packet)
167 GIFContext *s = avctx->priv_data;
168 AVFrame *const p = &s->picture;
169 uint8_t *outbuf_ptr, *end;
172 if ((ret = ff_alloc_packet2(avctx, pkt, avctx->width*avctx->height*7/5 + FF_MIN_BUFFER_SIZE)) < 0)
174 outbuf_ptr = pkt->data;
175 end = pkt->data + pkt->size;
178 p->pict_type = AV_PICTURE_TYPE_I;
180 gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
181 gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
183 pkt->size = outbuf_ptr - pkt->data;
184 pkt->flags |= AV_PKT_FLAG_KEY;
190 static int gif_encode_close(AVCodecContext *avctx)
192 GIFContext *s = avctx->priv_data;
199 AVCodec ff_gif_encoder = {
201 .type = AVMEDIA_TYPE_VIDEO,
202 .id = AV_CODEC_ID_GIF,
203 .priv_data_size = sizeof(GIFContext),
204 .init = gif_encode_init,
205 .encode2 = gif_encode_frame,
206 .close = gif_encode_close,
207 .pix_fmts = (const enum AVPixelFormat[]){
208 AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8, AV_PIX_FMT_RGB4_BYTE, AV_PIX_FMT_BGR4_BYTE,
209 AV_PIX_FMT_GRAY8, AV_PIX_FMT_PAL8, AV_PIX_FMT_NONE
211 .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),