On Sat, 20 Feb 2021, Derek Buitenhuis wrote:
This option will disable the writing of the global palette in global
GIF header if it is set to 0, causing only the frame-level palette
to ever be written.
This will be useful later on when further frame-level palette
optimizations are introduced.
The default is 1, which maintains current default behavior.
Signed-off-by: Derek Buitenhuis <derek.buitenh...@gmail.com>
---
Does this need a avcodec minor/patch version bump?
---
libavcodec/gif.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
docs update is missing for the new option.
Regards,
Marton
diff --git a/libavcodec/gif.c b/libavcodec/gif.c
index de41992851..8c07ee2769 100644
--- a/libavcodec/gif.c
+++ b/libavcodec/gif.c
@@ -51,6 +51,7 @@ typedef struct GIFContext {
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;
@@ -293,12 +294,14 @@ static int gif_image_write_image(AVCodecContext *avctx,
bcid = get_palette_transparency_index(global_palette);
- bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256
entries */
+ 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);
- for (int i = 0; i < 256; i++) {
- const uint32_t v = global_palette[i] & 0xffffff;
- bytestream_put_be24(bytestream, v);
+ 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);
+ }
}
}
@@ -330,15 +333,16 @@ static int gif_image_write_image(AVCodecContext *avctx,
bytestream_put_le16(bytestream, width);
bytestream_put_le16(bytestream, height);
- if (!palette) {
- bytestream_put_byte(bytestream, 0x00); /* flags */
- } else {
+ if (palette || !s->use_global_palette) {
+ const uint32_t *pal = palette ? palette : s->palette;
unsigned i;
bytestream_put_byte(bytestream, 1<<7 | 0x7); /* flags */
for (i = 0; i < AVPALETTE_COUNT; i++) {
- const uint32_t v = palette[i];
+ const uint32_t v = pal[i];
bytestream_put_be24(bytestream, v);
}
+ } else {
+ bytestream_put_byte(bytestream, 0x00); /* flags */
}
bytestream_put_byte(bytestream, 0x08);
@@ -473,6 +477,7 @@ static const AVOption gif_options[] = {
{ "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 }
};
--
2.30.0
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