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| author | Nicolas George <nicolas.george@normalesup.org> | 2013-01-01 17:06:04 +0100 |
|---|---|---|
| committer | Nicolas George <nicolas.george@normalesup.org> | 2013-01-01 20:07:37 +0100 |
| commit | 5ed5e90f2ae299cbec66996860d794771a85fee8 (patch) | |
| tree | 42dbfc175bee04454d14efe83b804f113be6fbc6 /libavcodec/dvdsubenc.c | |
| parent | 8dbbaf568ed9b9c76af596fc7daecbe1b971a7ce (diff) | |
| download | ffmpeg-5ed5e90f2ae299cbec66996860d794771a85fee8.tar.gz | |
lavc/dvdsubenc: improve color distance function.
Consider the color space as an hypercone with apex alpha=0
and base alpha=1 instead of an hypercube.
Make the encoder consider very transparent colors more similar
even if the hue is very different.
This corresponds roughly to using the alpha as a weight for the
color difference.
Only 4 bits of alpha are used, because this is what dvdsub uses,
and it avoids overflows.
Fix trac ticket #2005.
Diffstat (limited to 'libavcodec/dvdsubenc.c')
| -rw-r--r-- | libavcodec/dvdsubenc.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/libavcodec/dvdsubenc.c b/libavcodec/dvdsubenc.c index bf54aa2863..cd041c3f24 100644 --- a/libavcodec/dvdsubenc.c +++ b/libavcodec/dvdsubenc.c @@ -94,10 +94,14 @@ static void dvd_encode_rle(uint8_t **pq, static int color_distance(uint32_t a, uint32_t b) { int r = 0, d, i; + int alpha_a = 8, alpha_b = 8; - for (i = 0; i < 32; i += 8) { - d = ((a >> i) & 0xFF) - ((b >> i) & 0xFF); + for (i = 24; i >= 0; i -= 8) { + d = alpha_a * (int)((a >> i) & 0xFF) - + alpha_b * (int)((b >> i) & 0xFF); r += d * d; + alpha_a = a >> 28; + alpha_b = b >> 28; } return r; } @@ -130,7 +134,8 @@ static void count_colors(AVCodecContext *avctx, unsigned hits[33], if (match) { best_d = INT_MAX; for (j = 0; j < 16; j++) { - d = color_distance(color & 0xFFFFFF, dvdc->global_palette[j]); + d = color_distance(0xFF000000 | color, + 0xFF000000 | dvdc->global_palette[j]); if (d < best_d) { best_d = d; best_j = j; |