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avfilter/elbg: Extend filter to include alpha values in the quantization procedure

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Usage example:

ffmpeg -y -loglevel verbose -i "..\fate-suite\apng\o_sample.png" -filter_complex "elbg=pal8=1:use_alpha=1" -frames:v 1 out.png

Signed-off-by: softworkz <softworkz@hotmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Soft Works 2021-09-26 04:57:25 +00:00 committed by Michael Niedermayer
parent 0e45886e6e
commit 8983c3d7e4
2 changed files with 20 additions and 9 deletions
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4
doc/filters.texi
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@ -11396,6 +11396,10 @@ will try to use a good random seed on a best effort basis.
@item pal8
Set pal8 output pixel format. This option does not work with codebook
length greater than 256. Default is disabled.
@item use_alpha
Include alpha values in the quantization calculation. Allows creating
palettized output images (e.g. PNG8) with multiple alpha smooth blending.
@end table
@section entropy

25
libavfilter/vf_elbg.c
View File

@ -46,6 +46,7 @@ typedef struct ELBGFilterContext {
int codebook_length;
const AVPixFmtDescriptor *pix_desc;
uint8_t rgba_map[4];
int use_alpha;
int pal8;
} ELBGFilterContext;
@ -60,6 +61,7 @@ static const AVOption elbg_options[] = {
{ "seed", "set the random seed", OFFSET(lfg_seed), AV_OPT_TYPE_INT64, {.i64 = -1}, -1, UINT32_MAX, FLAGS },
{ "s", "set the random seed", OFFSET(lfg_seed), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1, UINT32_MAX, FLAGS },
{ "pal8", "set the pal8 output", OFFSET(pal8), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },
{ "use_alpha", "use alpha channel for mapping", OFFSET(use_alpha), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
{ NULL }
};
@ -105,7 +107,7 @@ static int query_formats(AVFilterContext *ctx)
return 0;
}
#define NB_COMPONENTS 3
#define NB_COMPONENTS 4
static int config_input(AVFilterLink *inlink)
{
@ -138,6 +140,7 @@ static int config_input(AVFilterLink *inlink)
#define R 0
#define G 1
#define B 2
#define A 3
static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
{
@ -148,6 +151,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
const uint8_t r_idx = elbg->rgba_map[R];
const uint8_t g_idx = elbg->rgba_map[G];
const uint8_t b_idx = elbg->rgba_map[B];
const uint8_t a_idx = elbg->rgba_map[A];
/* build the codeword */
p0 = frame->data[0];
@ -155,9 +159,10 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
for (i = 0; i < inlink->h; i++) {
p = p0;
for (j = 0; j < inlink->w; j++) {
elbg->codeword[k++] = p[r_idx];
elbg->codeword[k++] = p[g_idx];
elbg->codeword[k++] = p[b_idx];
elbg->codeword[k++] = p[g_idx];
elbg->codeword[k++] = p[r_idx];
elbg->codeword[k++] = elbg->use_alpha ? p[a_idx] : 0xff;
p += elbg->pix_desc->nb_components;
}
p0 += frame->linesize[0];
@ -188,10 +193,11 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
p0 = (uint8_t *)out->data[0];
for (i = 0; i < elbg->codebook_length; i++) {
pal[i] = 0xFFU << 24 |
(elbg->codebook[i*3 ] << 16) |
(elbg->codebook[i*3+1] << 8) |
elbg->codebook[i*3+2];
const int al = elbg->use_alpha ? elbg->codebook[i*4+3] : 0xff;
pal[i] = al << 24 |
(elbg->codebook[i*4+2] << 16) |
(elbg->codebook[i*4+1] << 8) |
elbg->codebook[i*4 ];
}
k = 0;
@ -214,9 +220,10 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
p = p0;
for (j = 0; j < inlink->w; j++) {
int cb_idx = NB_COMPONENTS * elbg->codeword_closest_codebook_idxs[k++];
p[r_idx] = elbg->codebook[cb_idx];
p[b_idx] = elbg->codebook[cb_idx];
p[g_idx] = elbg->codebook[cb_idx+1];
p[b_idx] = elbg->codebook[cb_idx+2];
p[r_idx] = elbg->codebook[cb_idx+2];
p[a_idx] = elbg->use_alpha ? elbg->codebook[cb_idx+3] : 0xFFu;
p += elbg->pix_desc->nb_components;
}
p0 += frame->linesize[0];