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avfilter/palettegen: always compute the box variance 

The variance computation is simple enough now (since we can use the axis
squared errors) that it doesn't need to have a complex lazy computation
logic.
This commit is contained in:
Clément Bœsch 2022-12-27 14:41:41 +01:00
parent 9e5f494d26
commit e49fc1a6ef
1 changed files with 9 additions and 33 deletions
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42
libavfilter/vf_palettegen.c
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@ -135,16 +135,6 @@ static int cmp_color(const void *a, const void *b)
return FFDIFFSIGN(box1->color , box2->color);
}
static av_always_inline int diff(const uint32_t a, const uint32_t b)
{
const uint8_t c1[] = {a >> 16 & 0xff, a >> 8 & 0xff, a & 0xff};
const uint8_t c2[] = {b >> 16 & 0xff, b >> 8 & 0xff, b & 0xff};
const int dr = c1[0] - c2[0];
const int dg = c1[1] - c2[1];
const int db = c1[2] - c2[2];
return dr*dr + dg*dg + db*db;
}
static void compute_box_stats(PaletteGenContext *s, struct range_box *box)
{
int avg[3];
@ -180,6 +170,8 @@ static void compute_box_stats(PaletteGenContext *s, struct range_box *box)
if (er2[2] >= er2[0] && er2[2] >= er2[1]) box->major_axis = 2;
if (er2[0] >= er2[1] && er2[0] >= er2[2]) box->major_axis = 0;
if (er2[1] >= er2[0] && er2[1] >= er2[2]) box->major_axis = 1; // prefer green again
box->variance = er2[0] + er2[1] + er2[2];
}
/**
@ -187,7 +179,7 @@ static void compute_box_stats(PaletteGenContext *s, struct range_box *box)
*/
static int get_next_box_id_to_split(PaletteGenContext *s)
{
int box_id, i, best_box_id = -1;
int box_id, best_box_id = -1;
int64_t max_variance = -1;
if (s->nb_boxes == s->max_colors - s->reserve_transparent)
@ -195,24 +187,9 @@ static int get_next_box_id_to_split(PaletteGenContext *s)
for (box_id = 0; box_id < s->nb_boxes; box_id++) {
struct range_box *box = &s->boxes[box_id];
if (s->boxes[box_id].len >= 2) {
if (box->variance == -1) {
int64_t variance = 0;
for (i = 0; i < box->len; i++) {
const struct color_ref *ref = s->refs[box->start + i];
variance += diff(ref->color, box->color) * ref->count;
}
box->variance = variance;
}
if (box->variance > max_variance) {
best_box_id = box_id;
max_variance = box->variance;
}
} else {
box->variance = -1;
if (s->boxes[box_id].len >= 2 && box->variance > max_variance) {
best_box_id = box_id;
max_variance = box->variance;
}
}
return best_box_id;
@ -261,8 +238,8 @@ static void split_box(PaletteGenContext *s, struct range_box *box, int n)
box->color = get_avg_color(s->refs, box);
new_box->color = get_avg_color(s->refs, new_box);
box->variance = -1;
new_box->variance = -1;
compute_box_stats(s, box);
compute_box_stats(s, new_box);
}
/**
@ -359,14 +336,13 @@ static AVFrame *get_palette_frame(AVFilterContext *ctx)
box->len = s->nb_refs;
box->sorted_by = -1;
box->color = get_avg_color(s->refs, box);
box->variance = -1;
compute_box_stats(s, box);
s->nb_boxes = 1;
while (box && box->len > 1) {
int i;
uint64_t median, box_weight;
compute_box_stats(s, box);
box_weight = box->weight;
ff_dlog(ctx, "box #%02X [%6d..%-6d] (%6d) w:%-6"PRIu64" sort by %c (already sorted:%c) ",