libavcodec/gif.c

   1 /*
   2  * GIF encoder.
   3  * Copyright (c) 2000 Fabrice Bellard
   4  * Copyright (c) 2002 Francois Revol
   5  * Copyright (c) 2006 Baptiste Coudurier
   6  *
   7  * first version by Francois Revol <revol@free.fr>
   8  *
   9  * This file is part of Libav.
  10  *
  11  * Libav is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; either
  14  * version 2.1 of the License, or (at your option) any later version.
  15  *
  16  * Libav is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with Libav; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  */
  25
  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 "internal.h"
  47 #include "lzw.h"
  48
  49 /* The GIF format uses reversed order for bitstreams... */
  50 /* at least they don't use PDP_ENDIAN :) */
  51 #define BITSTREAM_WRITER_LE
  52
  53 #include "put_bits.h"
  54
  55 typedef struct GIFContext {
  56     LZWState *lzw;
  57     uint8_t *buf;
  58 } GIFContext;
  59
  60 /* GIF header */
  61 static 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
  85 static 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 = 0, 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
 129 static av_cold int gif_encode_init(AVCodecContext *avctx)
 130 {
 131     GIFContext *s = avctx->priv_data;
 132
 133 #if FF_API_CODED_FRAME
 134 FF_DISABLE_DEPRECATION_WARNINGS
 135     avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
 136     avctx->coded_frame->key_frame = 1;
 137 FF_ENABLE_DEPRECATION_WARNINGS
 138 #endif
 139
 140     s->lzw = av_mallocz(ff_lzw_encode_state_size);
 141     if (!s->lzw)
 142         return AVERROR(ENOMEM);
 143     s->buf = av_malloc(avctx->width*avctx->height*2);
 144     if (!s->buf)
 145          return AVERROR(ENOMEM);
 146     return 0;
 147 }
 148
 149 /* better than nothing gif encoder */
 150 static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
 151                             const AVFrame *pict, int *got_packet)
 152 {
 153     uint8_t *outbuf_ptr, *end;
 154     int ret;
 155
 156     if ((ret = ff_alloc_packet(pkt, avctx->width*avctx->height*7/5 + AV_INPUT_BUFFER_MIN_SIZE)) < 0) {
 157         av_log(avctx, AV_LOG_ERROR, "Error getting output packet.\n");
 158         return ret;
 159     }
 160     outbuf_ptr = pkt->data;
 161     end        = pkt->data + pkt->size;
 162
 163     gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
 164     gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
 165
 166     pkt->size   = outbuf_ptr - pkt->data;
 167     pkt->flags |= AV_PKT_FLAG_KEY;
 168     *got_packet = 1;
 169
 170     return 0;
 171 }
 172
 173 static int gif_encode_close(AVCodecContext *avctx)
 174 {
 175     GIFContext *s = avctx->priv_data;
 176
 177     av_freep(&s->lzw);
 178     av_freep(&s->buf);
 179     return 0;
 180 }
 181
 182 AVCodec ff_gif_encoder = {
 183     .name           = "gif",
 184     .long_name      = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
 185     .type           = AVMEDIA_TYPE_VIDEO,
 186     .id             = AV_CODEC_ID_GIF,
 187     .priv_data_size = sizeof(GIFContext),
 188     .init           = gif_encode_init,
 189     .encode2        = gif_encode_frame,
 190     .close          = gif_encode_close,
 191     .pix_fmts       = (const enum AVPixelFormat[]){
 192         AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8, AV_PIX_FMT_RGB4_BYTE, AV_PIX_FMT_BGR4_BYTE,
 193         AV_PIX_FMT_GRAY8, AV_PIX_FMT_PAL8, AV_PIX_FMT_NONE
 194     },
 195 };