1/*
2 * GIF encoder.
3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2002 Francois Revol
5 * Copyright (c) 2006 Baptiste Coudurier
6 *
7 * This file is part of FFmpeg.
8 *
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.
13 *
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.
18 *
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
22 */
23
24/*
25 * First version by Francois Revol revol@free.fr
26 *
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).
32 *
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
37 *
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.
42 */
43
44#include "avcodec.h"
45#include "bytestream.h"
46#include "lzw.h"
47
48/* The GIF format uses reversed order for bitstreams... */
49/* at least they don't use PDP_ENDIAN :) */
50#define BITSTREAM_WRITER_LE
51
52#include "put_bits.h"
53
54typedef struct {
55    AVFrame picture;
56    LZWState *lzw;
57    uint8_t *buf;
58} GIFContext;
59
60/* GIF header */
61static int gif_image_write_header(AVCodecContext *avctx,
62                                  uint8_t **bytestream, uint32_t *palette)
63{
64    int i;
65    unsigned int v;
66
67    bytestream_put_buffer(bytestream, "GIF", 3);
68    bytestream_put_buffer(bytestream, "89a", 3);
69    bytestream_put_le16(bytestream, avctx->width);
70    bytestream_put_le16(bytestream, avctx->height);
71
72    bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
73    bytestream_put_byte(bytestream, 0x1f); /* background color index */
74    bytestream_put_byte(bytestream, 0); /* aspect ratio */
75
76    /* the global palette */
77    for(i=0;i<256;i++) {
78        v = palette[i];
79        bytestream_put_be24(bytestream, v);
80    }
81
82    return 0;
83}
84
85static int gif_image_write_image(AVCodecContext *avctx,
86                                 uint8_t **bytestream, uint8_t *end,
87                                 const uint8_t *buf, int linesize)
88{
89    GIFContext *s = avctx->priv_data;
90    int len, height;
91    const uint8_t *ptr;
92    /* image block */
93
94    bytestream_put_byte(bytestream, 0x2c);
95    bytestream_put_le16(bytestream, 0);
96    bytestream_put_le16(bytestream, 0);
97    bytestream_put_le16(bytestream, avctx->width);
98    bytestream_put_le16(bytestream, avctx->height);
99    bytestream_put_byte(bytestream, 0x00); /* flags */
100    /* no local clut */
101
102    bytestream_put_byte(bytestream, 0x08);
103
104    ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,
105                       12, FF_LZW_GIF, put_bits);
106
107    ptr = buf;
108    for (height = avctx->height; height--;) {
109        len += ff_lzw_encode(s->lzw, ptr, avctx->width);
110        ptr += linesize;
111    }
112    len += ff_lzw_encode_flush(s->lzw, flush_put_bits);
113
114    ptr = s->buf;
115    while (len > 0) {
116        int size = FFMIN(255, len);
117        bytestream_put_byte(bytestream, size);
118        if (end - *bytestream < size)
119            return -1;
120        bytestream_put_buffer(bytestream, ptr, size);
121        ptr += size;
122        len -= size;
123    }
124    bytestream_put_byte(bytestream, 0x00); /* end of image block */
125    bytestream_put_byte(bytestream, 0x3b);
126    return 0;
127}
128
129static av_cold int gif_encode_init(AVCodecContext *avctx)
130{
131    GIFContext *s = avctx->priv_data;
132
133    avctx->coded_frame = &s->picture;
134    s->lzw = av_mallocz(ff_lzw_encode_state_size);
135    if (!s->lzw)
136        return AVERROR(ENOMEM);
137    s->buf = av_malloc(avctx->width*avctx->height*2);
138    if (!s->buf)
139         return AVERROR(ENOMEM);
140    return 0;
141}
142
143/* better than nothing gif encoder */
144static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)
145{
146    GIFContext *s = avctx->priv_data;
147    AVFrame *pict = data;
148    AVFrame *const p = (AVFrame *)&s->picture;
149    uint8_t *outbuf_ptr = outbuf;
150    uint8_t *end = outbuf + buf_size;
151
152    *p = *pict;
153    p->pict_type = FF_I_TYPE;
154    p->key_frame = 1;
155    gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
156    gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
157    return outbuf_ptr - outbuf;
158}
159
160static int gif_encode_close(AVCodecContext *avctx)
161{
162    GIFContext *s = avctx->priv_data;
163
164    av_freep(&s->lzw);
165    av_freep(&s->buf);
166    return 0;
167}
168
169AVCodec gif_encoder = {
170    "gif",
171    AVMEDIA_TYPE_VIDEO,
172    CODEC_ID_GIF,
173    sizeof(GIFContext),
174    gif_encode_init,
175    gif_encode_frame,
176    gif_encode_close,
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)"),
179};
180