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avcodec/gif: add support for alpha

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Based on patch by Bjorn Roche.

Fixes #6813.
pull/302/head
Paul B Mahol 6 years ago
parent faca28c264
commit 3f8cdd4ee3
1 changed files with 144 additions and 24 deletions
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  1. 168
      libavcodec/gif.c

168
libavcodec/gif.c
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@ -2,6 +2,8 @@
* 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>
*
@ -60,6 +62,27 @@ enum {
GF_TRANSDIFF = 1<<1,
};
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;
@ -94,17 +117,91 @@ static int pick_palette_entry(const uint8_t *buf, int linesize, int w, int h)
return -1;
}
static int gif_image_write_image(AVCodecContext *avctx,
uint8_t **bytestream, uint8_t *end,
const uint32_t *palette,
static void gif_crop_translucent(AVCodecContext *avctx,
const uint8_t *buf, const int linesize,
AVPacket *pkt)
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[w * *y_start + i] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
(*y_start)++;
}
// crop bottom
while (y_end < h) {
int is_trans = 1;
for (int i = 0; i < w; i++) {
if (buf[w * 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[w * i + *x_start] != trans) {
is_trans = 0;
break;
}
}
if (!is_trans)
break;
(*x_start)++;
}
// crop right
while (x_end < w) {
int is_trans = 1;
for (int i = *y_start; i < y_end; i++) {
if (buf[w * 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;
int 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;
/* Crop image */
if ((s->flags & GF_OFFSETTING) && s->last_frame && !palette) {
@ -114,34 +211,34 @@ static int gif_image_write_image(AVCodecContext *avctx,
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))
while (*y_start < y_end) {
if (memcmp(ref + *y_start*ref_linesize, buf + *y_start*linesize, *width))
break;
y_start++;
(*y_start)++;
}
while (y_end > y_start) {
if (memcmp(ref + y_end*ref_linesize, buf + y_end*linesize, width))
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;
*height = y_end + 1 - *y_start;
/* skip common columns */
while (x_start < x_end) {
while (*x_start < x_end) {
int same_column = 1;
for (y = y_start; y <= y_end; y++) {
if (ref[y*ref_linesize + x_start] != buf[y*linesize + x_start]) {
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++;
(*x_start)++;
}
while (x_end > x_start) {
while (x_end > *x_start) {
int same_column = 1;
for (y = y_start; y <= y_end; y++) {
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;
@ -151,10 +248,32 @@ static int gif_image_write_image(AVCodecContext *avctx,
break;
x_end--;
}
width = x_end + 1 - x_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);
*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;
if (!s->is_first_frame && 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->is_first_frame) { /* GIF header */
@ -191,16 +310,17 @@ static int gif_image_write_image(AVCodecContext *avctx,
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;
bcid = (honor_transparency && trans >= 0) ? trans : get_palette_transparency_index(palette);
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, 1<<2 | (bcid >= 0));
bytestream_put_byte(bytestream, disposal<<2 | (bcid >= 0));
bytestream_put_le16(bytestream, 5); // default delay
bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid);
bytestream_put_byte(bytestream, 0x00);

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