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avcodec/gif: add support for alpha
Based on patch by Bjorn Roche. Fixes #6813.
This commit is contained in:
Paul B Mahol
parent
faca28c264
commit
3f8cdd4ee3
168
libavcodec/gif.c
168
libavcodec/gif.c
@ -2,6 +2,8 @@
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* Copyright (c) 2000 Fabrice Bellard
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* Copyright (c) 2002 Francois Revol
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* Copyright (c) 2006 Baptiste Coudurier
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* Copyright (c) 2018 Bjorn Roche
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* Copyright (c) 2018 Paul B Mahol
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*
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* first version by Francois Revol <revol@free.fr>
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*
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@ -60,6 +62,27 @@ enum {
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GF_TRANSDIFF = 1<<1,
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};
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static int is_image_translucent(AVCodecContext *avctx,
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const uint8_t *buf, const int linesize)
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{
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GIFContext *s = avctx->priv_data;
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int trans = s->transparent_index;
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if (trans < 0)
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return 0;
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for (int y = 0; y < avctx->height; y++) {
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for (int x = 0; x < avctx->width; x++) {
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if (buf[x] == trans) {
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return 1;
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}
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}
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buf += linesize;
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}
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return 0;
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}
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static int get_palette_transparency_index(const uint32_t *palette)
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{
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int transparent_color_index = -1;
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@ -94,17 +117,91 @@ static int pick_palette_entry(const uint8_t *buf, int linesize, int w, int h)
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return -1;
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}
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static int gif_image_write_image(AVCodecContext *avctx,
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uint8_t **bytestream, uint8_t *end,
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const uint32_t *palette,
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static void gif_crop_translucent(AVCodecContext *avctx,
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const uint8_t *buf, const int linesize,
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AVPacket *pkt)
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int *width, int *height,
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int *x_start, int *y_start)
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{
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GIFContext *s = avctx->priv_data;
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int trans = s->transparent_index;
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/* Crop image */
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if ((s->flags & GF_OFFSETTING) && trans >= 0) {
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const int w = avctx->width;
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const int h = avctx->height;
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int x_end = w - 1,
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y_end = h - 1;
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// crop top
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while (*y_start < y_end) {
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int is_trans = 1;
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for (int i = 0; i < w; i++) {
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if (buf[w * *y_start + i] != trans) {
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is_trans = 0;
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break;
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}
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}
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if (!is_trans)
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break;
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(*y_start)++;
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}
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// crop bottom
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while (y_end < h) {
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int is_trans = 1;
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for (int i = 0; i < w; i++) {
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if (buf[w * y_end + i] != trans) {
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is_trans = 0;
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break;
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}
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}
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if (!is_trans)
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break;
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y_end--;
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}
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// crop left
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while (*x_start < x_end) {
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int is_trans = 1;
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for (int i = *y_start; i < y_end; i++) {
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if (buf[w * i + *x_start] != trans) {
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is_trans = 0;
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break;
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}
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}
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if (!is_trans)
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break;
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(*x_start)++;
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}
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// crop right
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while (x_end < w) {
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int is_trans = 1;
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for (int i = *y_start; i < y_end; i++) {
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if (buf[w * i + x_end] != trans) {
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is_trans = 0;
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break;
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}
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}
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if (!is_trans)
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break;
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x_end--;
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}
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*height = y_end + 1 - *y_start;
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*width = x_end + 1 - *x_start;
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av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n",
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*width, *height, *x_start, *y_start, avctx->width, avctx->height);
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}
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}
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static void gif_crop_opaque(AVCodecContext *avctx,
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const uint32_t *palette,
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const uint8_t *buf, const int linesize,
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int *width, int *height, int *x_start, int *y_start)
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{
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GIFContext *s = avctx->priv_data;
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int len = 0, height = avctx->height, width = avctx->width, x, y;
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int x_start = 0, y_start = 0, trans = s->transparent_index;
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int bcid = -1, honor_transparency = (s->flags & GF_TRANSDIFF) && s->last_frame && !palette;
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const uint8_t *ptr;
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/* Crop image */
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if ((s->flags & GF_OFFSETTING) && s->last_frame && !palette) {
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@ -114,34 +211,34 @@ static int gif_image_write_image(AVCodecContext *avctx,
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y_end = avctx->height - 1;
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/* skip common lines */
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while (y_start < y_end) {
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if (memcmp(ref + y_start*ref_linesize, buf + y_start*linesize, width))
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while (*y_start < y_end) {
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if (memcmp(ref + *y_start*ref_linesize, buf + *y_start*linesize, *width))
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break;
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y_start++;
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(*y_start)++;
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}
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while (y_end > y_start) {
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if (memcmp(ref + y_end*ref_linesize, buf + y_end*linesize, width))
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while (y_end > *y_start) {
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if (memcmp(ref + y_end*ref_linesize, buf + y_end*linesize, *width))
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break;
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y_end--;
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}
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height = y_end + 1 - y_start;
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*height = y_end + 1 - *y_start;
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/* skip common columns */
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while (x_start < x_end) {
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while (*x_start < x_end) {
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int same_column = 1;
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for (y = y_start; y <= y_end; y++) {
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if (ref[y*ref_linesize + x_start] != buf[y*linesize + x_start]) {
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for (int y = *y_start; y <= y_end; y++) {
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if (ref[y*ref_linesize + *x_start] != buf[y*linesize + *x_start]) {
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same_column = 0;
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break;
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}
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}
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if (!same_column)
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break;
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x_start++;
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(*x_start)++;
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}
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while (x_end > x_start) {
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while (x_end > *x_start) {
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int same_column = 1;
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for (y = y_start; y <= y_end; y++) {
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for (int y = *y_start; y <= y_end; y++) {
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if (ref[y*ref_linesize + x_end] != buf[y*linesize + x_end]) {
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same_column = 0;
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break;
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@ -151,10 +248,32 @@ static int gif_image_write_image(AVCodecContext *avctx,
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break;
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x_end--;
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}
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width = x_end + 1 - x_start;
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*width = x_end + 1 - *x_start;
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av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n",
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width, height, x_start, y_start, avctx->width, avctx->height);
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*width, *height, *x_start, *y_start, avctx->width, avctx->height);
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}
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}
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static int gif_image_write_image(AVCodecContext *avctx,
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uint8_t **bytestream, uint8_t *end,
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const uint32_t *palette,
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const uint8_t *buf, const int linesize,
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AVPacket *pkt)
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{
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GIFContext *s = avctx->priv_data;
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int disposal, len = 0, height = avctx->height, width = avctx->width, x, y;
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int x_start = 0, y_start = 0, trans = s->transparent_index;
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int bcid = -1, honor_transparency = (s->flags & GF_TRANSDIFF) && s->last_frame && !palette;
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const uint8_t *ptr;
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if (!s->is_first_frame && is_image_translucent(avctx, buf, linesize)) {
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gif_crop_translucent(avctx, buf, linesize, &width, &height, &x_start, &y_start);
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honor_transparency = 0;
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disposal = GCE_DISPOSAL_BACKGROUND;
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} else {
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gif_crop_opaque(avctx, palette, buf, linesize, &width, &height, &x_start, &y_start);
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disposal = GCE_DISPOSAL_INPLACE;
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}
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if (s->is_first_frame) { /* GIF header */
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@ -191,16 +310,17 @@ static int gif_image_write_image(AVCodecContext *avctx,
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if (trans < 0) // TODO, patch welcome
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av_log(avctx, AV_LOG_DEBUG, "No available color, can not use transparency\n");
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}
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if (trans < 0)
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honor_transparency = 0;
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bcid = (honor_transparency && trans >= 0) ? trans : get_palette_transparency_index(palette);
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bcid = honor_transparency || disposal == GCE_DISPOSAL_BACKGROUND ? trans : get_palette_transparency_index(palette);
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/* graphic control extension */
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bytestream_put_byte(bytestream, GIF_EXTENSION_INTRODUCER);
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bytestream_put_byte(bytestream, GIF_GCE_EXT_LABEL);
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bytestream_put_byte(bytestream, 0x04); /* block size */
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bytestream_put_byte(bytestream, 1<<2 | (bcid >= 0));
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bytestream_put_byte(bytestream, disposal<<2 | (bcid >= 0));
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bytestream_put_le16(bytestream, 5); // default delay
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bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid);
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bytestream_put_byte(bytestream, 0x00);
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