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ffmpeg/libavcodec/gif.c

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/*
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2002 Francois Revol
* Copyright (c) 2006 Baptiste Coudurier
* Copyright (c) 2018 Bjorn Roche
* Copyright (c) 2018 Paul B Mahol
*
* 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
*/
/**
* @file
* GIF encoder
* @see http://www.w3.org/Graphics/GIF/spec-gif89a.txt
*/
#include "libavutil/opt.h"
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "encode.h"
#include "lzw.h"
#include "gif.h"
#define DEFAULT_TRANSPARENCY_INDEX 0x1f
typedef struct GIFContext {
const AVClass *class;
LZWState *lzw;
uint8_t *buf;
uint8_t *shrunk_buf;
int buf_size;
AVFrame *last_frame;
int flags;
int image;
int use_global_palette;
uint32_t palette[AVPALETTE_COUNT]; ///< local reference palette for !pal8
int palette_loaded;
int transparent_index;
uint8_t *tmpl; ///< temporary line buffer
} GIFContext;
enum {
GF_OFFSETTING = 1<<0,
GF_TRANSDIFF = 1<<1,
};
static void shrink_palette(const uint32_t *src, uint8_t *map,
uint32_t *dst, size_t *palette_count)
{
size_t colors_seen = 0;
for (size_t i = 0; i < AVPALETTE_COUNT; i++) {
int seen = 0;
for (size_t c = 0; c < colors_seen; c++) {
if (src[i] == dst[c]) {
seen = 1;
break;
}
}
if (!seen) {
dst[colors_seen] = src[i];
map[i] = colors_seen;
colors_seen++;
}
}
*palette_count = colors_seen;
}
static void remap_frame_to_palette(const uint8_t *src, int src_linesize,
uint8_t *dst, int dst_linesize,
int w, int h, uint8_t *map)
{
for (int i = 0; i < h; i++)
for (int j = 0; j < w; j++)
dst[i * dst_linesize + j] = map[src[i * src_linesize + j]];
}
static int is_image_translucent(AVCodecContext *avctx,
const uint8_t *buf, const int linesize)
{
GIFContext *s = avctx->priv_data;
int trans = s->transparent_index;
if (trans < 0)
return 0;
for (int y = 0; y < avctx->height; y++) {
for (int x = 0; x < avctx->width; x++) {
if (buf[x] == trans) {
return 1;
}
}
buf += linesize;
}
return 0;
}
static int get_palette_transparency_index(const uint32_t *palette)
{
int transparent_color_index = -1;
unsigned i, smallest_alpha = 0xff;
if (!palette)
return -1;
for (i = 0; i < AVPALETTE_COUNT; i++) {
const uint32_t v = palette[i];
if (v >> 24 < smallest_alpha) {
smallest_alpha = v >> 24;
transparent_color_index = i;
}
}
return smallest_alpha < 128 ? transparent_color_index : -1;
}
static int pick_palette_entry(const uint8_t *buf, int linesize, int w, int h)
{
int histogram[AVPALETTE_COUNT] = {0};
int x, y, i;
for (y = 0; y < h; y++) {
for (x = 0; x < w; x++)
histogram[buf[x]]++;
buf += linesize;
}
for (i = 0; i < FF_ARRAY_ELEMS(histogram); i++)
if (!histogram[i])
return i;
return -1;
}
static void gif_crop_translucent(AVCodecContext *avctx,
const uint8_t *buf, const int linesize,
int *width, int *height,
int *x_start, int *y_start)
{
GIFContext *s = avctx->priv_data;
int trans = s->transparent_index;
/* Crop image */
if ((s->flags & GF_OFFSETTING) && trans >= 0) {
const int w = avctx->width;
const int h = avctx->height;
int x_end = w - 1,
y_end = h - 1;
// crop top
while (*y_start < y_end) {
int is_trans = 1;
for (int i = 0; i < w; i++) {
if (buf[linesize * *y_start + i] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
(*y_start)++;
}
// crop bottom
while (y_end > *y_start) {
int is_trans = 1;
for (int i = 0; i < w; i++) {
if (buf[linesize * y_end + i] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
y_end--;
}
// crop left
while (*x_start < x_end) {
int is_trans = 1;
for (int i = *y_start; i < y_end; i++) {
if (buf[linesize * i + *x_start] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
(*x_start)++;
}
// crop right
while (x_end > *x_start) {
int is_trans = 1;
for (int i = *y_start; i < y_end; i++) {
if (buf[linesize * i + x_end] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
x_end--;
}
*height = y_end + 1 - *y_start;
*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);
}
}
static void gif_crop_opaque(AVCodecContext *avctx,
const uint32_t *palette,
const uint8_t *buf, const int linesize,
int *width, int *height, int *x_start, int *y_start)
{
GIFContext *s = avctx->priv_data;
/* Crop image */
if ((s->flags & GF_OFFSETTING) && 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 < y_end) {
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 < x_end) {
int same_column = 1;
for (int 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 (int 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);
}
}
static int gif_image_write_image(AVCodecContext *avctx,
uint8_t **bytestream, uint8_t *end,
const uint32_t *palette,
const uint8_t *buf, const int linesize,
AVPacket *pkt)
{
GIFContext *s = avctx->priv_data;
int disposal, len = 0, height = avctx->height, width = avctx->width, x, y;
int x_start = 0, y_start = 0, trans = s->transparent_index;
int bcid = -1, honor_transparency = (s->flags & GF_TRANSDIFF) && s->last_frame && !palette;
const uint8_t *ptr;
uint32_t shrunk_palette[AVPALETTE_COUNT];
uint8_t map[AVPALETTE_COUNT] = { 0 };
size_t shrunk_palette_count = 0;
/*
* We memset to 0xff instead of 0x00 so that the transparency detection
* doesn't pick anything after the palette entries as the transparency
* index, and because GIF89a requires us to always write a power-of-2
* number of palette entries.
*/
memset(shrunk_palette, 0xff, AVPALETTE_SIZE);
if (!s->image && is_image_translucent(avctx, buf, linesize)) {
gif_crop_translucent(avctx, buf, linesize, &width, &height, &x_start, &y_start);
honor_transparency = 0;
disposal = GCE_DISPOSAL_BACKGROUND;
} else {
gif_crop_opaque(avctx, palette, buf, linesize, &width, &height, &x_start, &y_start);
disposal = GCE_DISPOSAL_INPLACE;
}
if (s->image || !avctx->frame_num) { /* GIF header */
const uint32_t *global_palette = palette ? palette : s->palette;
const AVRational sar = avctx->sample_aspect_ratio;
int64_t aspect = 0;
if (sar.num > 0 && sar.den > 0) {
aspect = sar.num * 64LL / sar.den - 15;
if (aspect < 0 || aspect > 255)
aspect = 0;
}
bytestream_put_buffer(bytestream, gif89a_sig, sizeof(gif89a_sig));
bytestream_put_le16(bytestream, avctx->width);
bytestream_put_le16(bytestream, avctx->height);
bcid = get_palette_transparency_index(global_palette);
bytestream_put_byte(bytestream, ((uint8_t) s->use_global_palette << 7) | 0x70 | (s->use_global_palette ? 7 : 0)); /* flags: global clut, 256 entries */
bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); /* background color index */
bytestream_put_byte(bytestream, aspect);
if (s->use_global_palette) {
for (int i = 0; i < 256; i++) {
const uint32_t v = global_palette[i] & 0xffffff;
bytestream_put_be24(bytestream, v);
}
}
}
if (honor_transparency && trans < 0) {
trans = pick_palette_entry(buf + y_start*linesize + x_start,
linesize, width, height);
if (trans < 0) // TODO, patch welcome
av_log(avctx, AV_LOG_DEBUG, "No available color, can not use transparency\n");
}
if (trans < 0)
honor_transparency = 0;
if (palette || !s->use_global_palette) {
const uint32_t *pal = palette ? palette : s->palette;
shrink_palette(pal, map, shrunk_palette, &shrunk_palette_count);
}
bcid = honor_transparency || disposal == GCE_DISPOSAL_BACKGROUND ? trans : get_palette_transparency_index(palette);
/* graphic control extension */
bytestream_put_byte(bytestream, GIF_EXTENSION_INTRODUCER);
bytestream_put_byte(bytestream, GIF_GCE_EXT_LABEL);
bytestream_put_byte(bytestream, 0x04); /* block size */
bytestream_put_byte(bytestream, disposal<<2 | (bcid >= 0));
bytestream_put_le16(bytestream, 5); // default delay
bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : (shrunk_palette_count ? map[bcid] : bcid));
bytestream_put_byte(bytestream, 0x00);
/* image block */
bytestream_put_byte(bytestream, GIF_IMAGE_SEPARATOR);
bytestream_put_le16(bytestream, x_start);
bytestream_put_le16(bytestream, y_start);
bytestream_put_le16(bytestream, width);
bytestream_put_le16(bytestream, height);
if (palette || !s->use_global_palette) {
unsigned pow2_count = av_log2(shrunk_palette_count - 1);
unsigned i;
bytestream_put_byte(bytestream, 1<<7 | pow2_count); /* flags */
for (i = 0; i < 1 << (pow2_count + 1); i++) {
const uint32_t v = shrunk_palette[i];
bytestream_put_be24(bytestream, v);
}
} else {
bytestream_put_byte(bytestream, 0x00); /* flags */
}
bytestream_put_byte(bytestream, 0x08);
ff_lzw_encode_init(s->lzw, s->buf, s->buf_size,
12, FF_LZW_GIF, 1);
if (shrunk_palette_count) {
if (!s->shrunk_buf) {
s->shrunk_buf = av_malloc(avctx->height * linesize);
if (!s->shrunk_buf) {
av_log(avctx, AV_LOG_ERROR, "Could not allocated remapped frame buffer.\n");
return AVERROR(ENOMEM);
}
}
remap_frame_to_palette(buf, linesize, s->shrunk_buf, linesize, avctx->width, avctx->height, map);
ptr = s->shrunk_buf + y_start*linesize + x_start;
} else {
ptr = buf + y_start*linesize + x_start;
}
if (honor_transparency) {
const int ref_linesize = s->last_frame->linesize[0];
const uint8_t *ref = s->last_frame->data[0] + y_start*ref_linesize + x_start;
for (y = 0; y < height; y++) {
memcpy(s->tmpl, ptr, width);
for (x = 0; x < width; x++)
if (ref[x] == ptr[x])
s->tmpl[x] = trans;
len += ff_lzw_encode(s->lzw, s->tmpl, width);
ptr += linesize;
ref += ref_linesize;
}
} else {
for (y = 0; y < height; y++) {
len += ff_lzw_encode(s->lzw, ptr, width);
ptr += linesize;
}
}
len += ff_lzw_encode_flush(s->lzw);
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);
}
s->transparent_index = -1;
s->lzw = av_mallocz(ff_lzw_encode_state_size);
s->buf_size = avctx->width*avctx->height*2 + 1000;
s->buf = av_malloc(s->buf_size);
s->tmpl = av_malloc(avctx->width);
if (!s->tmpl || !s->buf || !s->lzw)
return AVERROR(ENOMEM);
if (avpriv_set_systematic_pal2(s->palette, avctx->pix_fmt) < 0)
av_assert0(avctx->pix_fmt == AV_PIX_FMT_PAL8);
return 0;
}
static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *pict, int *got_packet)
{
GIFContext *s = avctx->priv_data;
uint8_t *outbuf_ptr, *end;
const uint32_t *palette = NULL;
int ret;
if ((ret = ff_alloc_packet(avctx, pkt, avctx->width*avctx->height*7/5 + AV_INPUT_BUFFER_MIN_SIZE)) < 0)
return ret;
outbuf_ptr = pkt->data;
end = pkt->data + pkt->size;
if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
palette = (uint32_t*)pict->data[1];
if (!s->palette_loaded) {
memcpy(s->palette, palette, AVPALETTE_SIZE);
s->transparent_index = get_palette_transparency_index(palette);
s->palette_loaded = 1;
} else if (!memcmp(s->palette, palette, AVPALETTE_SIZE)) {
palette = NULL;
}
}
gif_image_write_image(avctx, &outbuf_ptr, end, palette,
pict->data[0], pict->linesize[0], pkt);
if (!s->last_frame && !s->image) {
s->last_frame = av_frame_alloc();
if (!s->last_frame)
return AVERROR(ENOMEM);
}
if (!s->image) {
av_frame_unref(s->last_frame);
ret = av_frame_ref(s->last_frame, pict);
if (ret < 0)
return ret;
}
pkt->size = outbuf_ptr - pkt->data;
if (s->image || !avctx->frame_num)
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_freep(&s->shrunk_buf);
s->buf_size = 0;
av_frame_free(&s->last_frame);
av_freep(&s->tmpl);
return 0;
}
#define OFFSET(x) offsetof(GIFContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
static const AVOption gif_options[] = {
{ "gifflags", "set GIF flags", OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = GF_OFFSETTING|GF_TRANSDIFF}, 0, INT_MAX, FLAGS, "flags" },
{ "offsetting", "enable picture offsetting", 0, AV_OPT_TYPE_CONST, {.i64=GF_OFFSETTING}, INT_MIN, INT_MAX, FLAGS, "flags" },
{ "transdiff", "enable transparency detection between frames", 0, AV_OPT_TYPE_CONST, {.i64=GF_TRANSDIFF}, INT_MIN, INT_MAX, FLAGS, "flags" },
{ "gifimage", "enable encoding only images per frame", OFFSET(image), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
{ "global_palette", "write a palette to the global gif header where feasible", OFFSET(use_global_palette), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },
{ NULL }
};
static const AVClass gif_class = {
.class_name = "GIF encoder",
.item_name = av_default_item_name,
.option = gif_options,
.version = LIBAVUTIL_VERSION_INT,
};
const FFCodec ff_gif_encoder = {
.p.name = "gif",
CODEC_LONG_NAME("GIF (Graphics Interchange Format)"),
.p.type = AVMEDIA_TYPE_VIDEO,
.p.id = AV_CODEC_ID_GIF,
.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
.priv_data_size = sizeof(GIFContext),
.init = gif_encode_init,
FF_CODEC_ENCODE_CB(gif_encode_frame),
.close = gif_encode_close,
.p.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
},
.p.priv_class = &gif_class,
.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
};
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