FFmpeg/libavcodec/gif.c
2013-04-18 00:24:25 +02:00

264 lines
8.3 KiB
C

/*
* GIF encoder.
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2002 Francois Revol
* Copyright (c) 2006 Baptiste Coudurier
*
* first version by Francois Revol <revol@free.fr>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* Features and limitations:
* - uses only a global standard palette
* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
*
* Reference documents:
* http://www.goice.co.jp/member/mo/formats/gif.html
* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
*/
#include "avcodec.h"
#include "bytestream.h"
#include "internal.h"
#include "lzw.h"
/* The GIF format uses reversed order for bitstreams... */
/* at least they don't use PDP_ENDIAN :) */
#define BITSTREAM_WRITER_LE
#include "put_bits.h"
typedef struct {
AVFrame picture;
LZWState *lzw;
uint8_t *buf;
AVFrame *last_frame;
} GIFContext;
static int gif_image_write_image(AVCodecContext *avctx,
uint8_t **bytestream, uint8_t *end,
const uint32_t *palette,
const uint8_t *buf, int linesize)
{
GIFContext *s = avctx->priv_data;
int len = 0, height = avctx->height, width = avctx->width, y;
int x_start = 0, y_start = 0;
const uint8_t *ptr;
/* Mark one colour as transparent if the input palette contains at least
* one colour that is more than 50% transparent. */
if (palette) {
unsigned i, smallest_alpha = 0xFF, alpha_component = 0;
for (i = 0; i < AVPALETTE_COUNT; i++) {
const uint32_t v = palette[i];
if (v >> 24 < smallest_alpha) {
smallest_alpha = v >> 24;
alpha_component = i;
}
}
if (smallest_alpha < 128) {
bytestream_put_byte(bytestream, 0x21); /* Extension Introducer */
bytestream_put_byte(bytestream, 0xf9); /* Graphic Control Label */
bytestream_put_byte(bytestream, 0x04); /* block length */
bytestream_put_byte(bytestream, 0x01); /* Transparent Color Flag */
bytestream_put_le16(bytestream, 0x00); /* no delay */
bytestream_put_byte(bytestream, alpha_component);
bytestream_put_byte(bytestream, 0x00);
}
}
/* Crop image */
// TODO support with palette change
if (s->last_frame && !palette) {
const uint8_t *ref = s->last_frame->data[0];
const int ref_linesize = s->last_frame->linesize[0];
int x_end = avctx->width - 1,
y_end = avctx->height - 1;
/* skip common lines */
while (y_start < height) {
if (memcmp(ref + y_start*ref_linesize, buf + y_start*linesize, width))
break;
y_start++;
}
while (y_end > y_start) {
if (memcmp(ref + y_end*ref_linesize, buf + y_end*linesize, width))
break;
y_end--;
}
height = y_end + 1 - y_start;
/* skip common columns */
while (x_start < width) {
int same_column = 1;
for (y = y_start; y < y_end; y++) {
if (ref[y*ref_linesize + x_start] != buf[y*linesize + x_start]) {
same_column = 0;
break;
}
}
if (!same_column)
break;
x_start++;
}
while (x_end > x_start) {
int same_column = 1;
for (y = y_start; y < y_end; y++) {
if (ref[y*ref_linesize + x_end] != buf[y*linesize + x_end]) {
same_column = 0;
break;
}
}
if (!same_column)
break;
x_end--;
}
width = x_end + 1 - x_start;
av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n",
width, height, x_start, y_start, avctx->width, avctx->height);
}
/* image block */
bytestream_put_byte(bytestream, 0x2c);
bytestream_put_le16(bytestream, x_start);
bytestream_put_le16(bytestream, y_start);
bytestream_put_le16(bytestream, width);
bytestream_put_le16(bytestream, height);
if (!palette) {
bytestream_put_byte(bytestream, 0x00); /* flags */
} else {
unsigned i;
bytestream_put_byte(bytestream, 1<<7 | 0x7); /* flags */
for (i = 0; i < AVPALETTE_COUNT; i++) {
const uint32_t v = palette[i];
bytestream_put_be24(bytestream, v);
}
}
bytestream_put_byte(bytestream, 0x08);
ff_lzw_encode_init(s->lzw, s->buf, width * height,
12, FF_LZW_GIF, put_bits);
ptr = buf + y_start*linesize + x_start;
for (y = 0; y < height; y++) {
len += ff_lzw_encode(s->lzw, ptr, width);
ptr += linesize;
}
len += ff_lzw_encode_flush(s->lzw, flush_put_bits);
ptr = s->buf;
while (len > 0) {
int size = FFMIN(255, len);
bytestream_put_byte(bytestream, size);
if (end - *bytestream < size)
return -1;
bytestream_put_buffer(bytestream, ptr, size);
ptr += size;
len -= size;
}
bytestream_put_byte(bytestream, 0x00); /* end of image block */
return 0;
}
static av_cold int gif_encode_init(AVCodecContext *avctx)
{
GIFContext *s = avctx->priv_data;
if (avctx->width > 65535 || avctx->height > 65535) {
av_log(avctx, AV_LOG_ERROR, "GIF does not support resolutions above 65535x65535\n");
return AVERROR(EINVAL);
}
avctx->coded_frame = &s->picture;
s->lzw = av_mallocz(ff_lzw_encode_state_size);
s->buf = av_malloc(avctx->width*avctx->height*2);
if (!s->buf || !s->lzw)
return AVERROR(ENOMEM);
return 0;
}
/* better than nothing gif encoder */
static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *pict, int *got_packet)
{
GIFContext *s = avctx->priv_data;
AVFrame *const p = &s->picture;
uint8_t *outbuf_ptr, *end;
const uint32_t *palette = NULL;
int ret;
if ((ret = ff_alloc_packet2(avctx, pkt, avctx->width*avctx->height*7/5 + FF_MIN_BUFFER_SIZE)) < 0)
return ret;
outbuf_ptr = pkt->data;
end = pkt->data + pkt->size;
*p = *pict;
p->pict_type = AV_PICTURE_TYPE_I;
p->key_frame = 1;
if (avctx->pix_fmt == AV_PIX_FMT_PAL8)
palette = (uint32_t*)p->data[1];
gif_image_write_image(avctx, &outbuf_ptr, end, palette, pict->data[0], pict->linesize[0]);
if (!s->last_frame) {
s->last_frame = av_frame_alloc();
if (!s->last_frame)
return AVERROR(ENOMEM);
}
av_frame_unref(s->last_frame);
ret = av_frame_ref(s->last_frame, (AVFrame*)pict);
if (ret < 0)
return ret;
pkt->size = outbuf_ptr - pkt->data;
pkt->flags |= AV_PKT_FLAG_KEY;
*got_packet = 1;
return 0;
}
static int gif_encode_close(AVCodecContext *avctx)
{
GIFContext *s = avctx->priv_data;
av_freep(&s->lzw);
av_freep(&s->buf);
av_frame_free(&s->last_frame);
return 0;
}
AVCodec ff_gif_encoder = {
.name = "gif",
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_GIF,
.priv_data_size = sizeof(GIFContext),
.init = gif_encode_init,
.encode2 = gif_encode_frame,
.close = gif_encode_close,
.pix_fmts = (const enum AVPixelFormat[]){
AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8, AV_PIX_FMT_RGB4_BYTE, AV_PIX_FMT_BGR4_BYTE,
AV_PIX_FMT_GRAY8, AV_PIX_FMT_PAL8, AV_PIX_FMT_NONE
},
.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
};