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| author | Mattias Andrée <m@maandree.se> | 2025-11-26 19:01:38 +0100 |
|---|---|---|
| committer | Mattias Andrée <m@maandree.se> | 2025-11-26 19:01:38 +0100 |
| commit | 7d15d0c247954edb224b35b7bfb5e8fe5d5d4fb7 (patch) | |
| tree | fc60b55a73e22b26b4bae6947017e036b25f0ec9 | |
| parent | Update README (diff) | |
| download | libquanta-7d15d0c247954edb224b35b7bfb5e8fe5d5d4fb7.tar.gz libquanta-7d15d0c247954edb224b35b7bfb5e8fe5d5d4fb7.tar.bz2 libquanta-7d15d0c247954edb224b35b7bfb5e8fe5d5d4fb7.tar.xz | |
Signed-off-by: Mattias Andrée <m@maandree.se>
| -rw-r--r-- | libquanta_vquantise_wu.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/libquanta_vquantise_wu.c b/libquanta_vquantise_wu.c index 55129f2..d148c96 100644 --- a/libquanta_vquantise_wu.c +++ b/libquanta_vquantise_wu.c @@ -8,7 +8,8 @@ struct channel_data { const struct libquanta_channel *ch; size_t subindex_multiplier; - size_t colour_shift; + size_t colour_shift_down; + size_t colour_shift_up; struct bigint *histogram; struct bigint whole; struct bigint half; @@ -63,7 +64,8 @@ compute_histogram(struct libquanta_image *image, struct histogram *histogram, st else abort(); square_subsum += (long double)v * (long double)v; - v >>= channels[ch].colour_shift; + v >>= channels[ch].colour_shift_down; + v <<= channels[ch].colour_shift_up; v += 1U; index += v * channels[ch].subindex_multiplier; bigint_add_small(&channels[ch].histogram[index], v); @@ -462,8 +464,8 @@ maximise(const struct cube *cube, size_t channel, const struct histogram *histog base_weight = bottom_over_occurrences(cube, channel, histogram, channels, nchannels); first = cube->bounds[channel].min + 1U; - last = cube->bounds[channel].max; - for (pos = first; pos < last; pos++) { /* TODO should `last` really be exclusive? */ + last = cube->bounds[channel].max; /* yes, the maximum should be excluded */ + for (pos = first; pos < last; pos++) { half_weight = top_over_occurrences(cube, channel, pos, histogram, channels, nchannels); half_weight += base_weight; if (!half_weight) @@ -698,7 +700,10 @@ libquanta_vquantise_wu(struct libquanta_palette *palette, va_list args) subindex_multiplier = 1U; for (i = nchannels; i--; subindex_multiplier *= ((1U << WORKING_BITS) + 1U)) { channels[i].subindex_multiplier = subindex_multiplier; - channels[i].colour_shift = channels[i].ch->bits_in > WORKING_BITS ? channels[i].ch->bits_in - WORKING_BITS : 0U; + if (channels[i].ch->bits_in > WORKING_BITS) + channels[i].colour_shift_down = channels[i].ch->bits_in - WORKING_BITS; + else if (channels[i].ch->bits_in < WORKING_BITS) + channels[i].colour_shift_up = WORKING_BITS - channels[i].ch->bits_in; } for (i = 0; i < nchannels; i++) { channels[i].histogram = calloc(subindex_multiplier, sizeof(*channels[i].histogram)); |