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
47/* The GIF format uses reversed order for bitstreams... */
48/* at least they don't use PDP_ENDIAN :) */
49#define BITSTREAM_WRITER_LE
50
51#include "bitstream.h"
52
53/* bitstream minipacket size */
54#define GIF_CHUNKS 100
55
56/* GIF header */
57static int gif_image_write_header(uint8_t **bytestream,
58                                  int width, int height,
59                                  uint32_t *palette)
60{
61    int i;
62    unsigned int v;
63
64    bytestream_put_buffer(bytestream, "GIF", 3);
65    bytestream_put_buffer(bytestream, "89a", 3);
66    bytestream_put_le16(bytestream, width);
67    bytestream_put_le16(bytestream, height);
68
69    bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
70    bytestream_put_byte(bytestream, 0x1f); /* background color index */
71    bytestream_put_byte(bytestream, 0); /* aspect ratio */
72
73    /* the global palette */
74    for(i=0;i<256;i++) {
75        v = palette[i];
76        bytestream_put_be24(bytestream, v);
77    }
78
79    return 0;
80}
81
82static int gif_image_write_image(uint8_t **bytestream,
83                                 int x1, int y1, int width, int height,
84                                 const uint8_t *buf, int linesize, int pix_fmt)
85{
86    PutBitContext p;
87    uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
88    int i, left, w;
89    const uint8_t *ptr;
90    /* image block */
91
92    bytestream_put_byte(bytestream, 0x2c);
93    bytestream_put_le16(bytestream, x1);
94    bytestream_put_le16(bytestream, y1);
95    bytestream_put_le16(bytestream, width);
96    bytestream_put_le16(bytestream, height);
97    bytestream_put_byte(bytestream, 0x00); /* flags */
98    /* no local clut */
99
100    bytestream_put_byte(bytestream, 0x08);
101
102    left= width * height;
103
104    init_put_bits(&p, buffer, 130);
105
106/*
107 * the thing here is the bitstream is written as little packets, with a size byte before
108 * but it's still the same bitstream between packets (no flush !)
109 */
110    ptr = buf;
111    w = width;
112    while(left>0) {
113
114        put_bits(&p, 9, 0x0100); /* clear code */
115
116        for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
117            put_bits(&p, 9, *ptr++);
118            if (--w == 0) {
119                w = width;
120                buf += linesize;
121                ptr = buf;
122            }
123        }
124
125        if(left<=GIF_CHUNKS) {
126            put_bits(&p, 9, 0x101); /* end of stream */
127            flush_put_bits(&p);
128        }
129        if(pbBufPtr(&p) - p.buf > 0) {
130            bytestream_put_byte(bytestream, pbBufPtr(&p) - p.buf); /* byte count of the packet */
131            bytestream_put_buffer(bytestream, p.buf, pbBufPtr(&p) - p.buf); /* the actual buffer */
132            p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
133        }
134        left-=GIF_CHUNKS;
135    }
136    bytestream_put_byte(bytestream, 0x00); /* end of image block */
137    bytestream_put_byte(bytestream, 0x3b);
138    return 0;
139}
140
141typedef struct {
142    AVFrame picture;
143} GIFContext;
144
145static av_cold int gif_encode_init(AVCodecContext *avctx)
146{
147    GIFContext *s = avctx->priv_data;
148
149    avctx->coded_frame = &s->picture;
150    return 0;
151}
152
153/* better than nothing gif encoder */
154static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)
155{
156    GIFContext *s = avctx->priv_data;
157    AVFrame *pict = data;
158    AVFrame *const p = (AVFrame *)&s->picture;
159    uint8_t *outbuf_ptr = outbuf;
160
161    *p = *pict;
162    p->pict_type = FF_I_TYPE;
163    p->key_frame = 1;
164    gif_image_write_header(&outbuf_ptr, avctx->width, avctx->height, (uint32_t *)pict->data[1]);
165    gif_image_write_image(&outbuf_ptr, 0, 0, avctx->width, avctx->height, pict->data[0], pict->linesize[0], PIX_FMT_PAL8);
166    return outbuf_ptr - outbuf;
167}
168
169AVCodec gif_encoder = {
170    "gif",
171    CODEC_TYPE_VIDEO,
172    CODEC_ID_GIF,
173    sizeof(GIFContext),
174    gif_encode_init,
175    gif_encode_frame,
176    NULL, //encode_end,
177    .pix_fmts= (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