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FFmpeg/libavcodec/gif.c
Andreas Rheinhardt 20f9727018 avcodec/codec_internal: Add FFCodec, hide internal part of AVCodec 
Up until now, codec.h contains both public and private parts
of AVCodec. This exposes the internals of AVCodec to users
and leads them into the temptation of actually using them
and forces us to forward-declare structures and types that
users can't use at all.

This commit changes this by adding a new structure FFCodec to
codec_internal.h that extends AVCodec, i.e. contains the public
AVCodec as first member; the private fields of AVCodec are moved
to this structure, leaving codec.h clean.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-03-21 01:33:09 +01:00

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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
*/
#define BITSTREAM_WRITER_LE
#include "libavutil/opt.h"
#include "libavutil/imgutils.h"
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "encode.h"
#include "lzw.h"
#include "gif.h"
#include "put_bits.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_number) { /* 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, (AVFrame*)pict);
if (ret < 0)
return ret;
}
pkt->size = outbuf_ptr - pkt->data;
if (s->image || !avctx->frame_number)
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",
.p.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
.p.type = AVMEDIA_TYPE_VIDEO,
.p.id = AV_CODEC_ID_GIF,
.priv_data_size = sizeof(GIFContext),
.init = gif_encode_init,
.encode2 = 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_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
};
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