diff options
| -rw-r--r-- | sixel.go | 30 |
1 files changed, 14 insertions, 16 deletions
@@ -76,12 +76,9 @@ func quickSelect(list []color.RGBA, k int, cmp func(color.RGBA, color.RGBA) int, } } -func bucketRange(colors []color.RGBA, bucketIdx int, rangeCache []int32) (rRange, gRange, bRange uint8) { +func bucketRange(colors []color.RGBA) color.RGBA { if len(colors) == 0 { - return 0, 0, 0 - } - if cached := rangeCache[bucketIdx]; cached >= 0 { - return uint8(cached >> 16), uint8(cached >> 8), uint8(cached) + return color.RGBA{} } var minR, minG, minB uint8 = math.MaxUint8, math.MaxUint8, math.MaxUint8 var maxR, maxG, maxB uint8 @@ -90,16 +87,14 @@ func bucketRange(colors []color.RGBA, bucketIdx int, rangeCache []int32) (rRange minG, maxG = min(minG, c.G), max(maxG, c.G) minB, maxB = min(minB, c.B), max(maxB, c.B) } - rRange, gRange, bRange = maxR-minR, maxG-minG, maxB-minB - rangeCache[bucketIdx] = int32(rRange)<<16 | int32(gRange)<<8 | int32(bRange) - return rRange, gRange, bRange + return color.RGBA{R: maxR - minR, G: maxG - minG, B: maxB - minB} } -func cutOnce(colors []color.RGBA, bucketIdx int, rangeCache []int32, rand *uint64) [2][]color.RGBA { +func cutOnce(colors []color.RGBA, bucketRange color.RGBA, rand *uint64) [2][]color.RGBA { if len(colors) == 0 { return [...][]color.RGBA{colors, colors} } - rRange, gRange, bRange := bucketRange(colors, bucketIdx, rangeCache) + rRange, gRange, bRange := bucketRange.R, bucketRange.G, bucketRange.B if rRange >= gRange && rRange >= bRange { quickSelect(colors, len(colors)/2, func(x, y color.RGBA) int { return int(x.R) - int(y.R) }, rand) } else if gRange >= rRange && gRange >= bRange { @@ -132,21 +127,24 @@ func medianCut(img image.Image) color.Palette { } } buckets := [][]color.RGBA{colors} - bucketRanges := []int32{-1} + bucketRanges := []color.RGBA{{}} randState := rand.Uint64() - for len(buckets) < 255 { + for { var bestRange uint8 var bestIdx int - for i, b := range buckets { - r := max(bucketRange(b, i, bucketRanges)) + for i, rng := range bucketRanges { + r := max(rng.R, rng.G, rng.B) if r >= bestRange { bestRange = r bestIdx = i } } - split := cutOnce(buckets[bestIdx], bestIdx, bucketRanges, &randState) + split := cutOnce(buckets[bestIdx], bucketRanges[bestIdx], &randState) buckets = slices.Replace(buckets, bestIdx, bestIdx+1, split[:]...) - bucketRanges = slices.Replace(bucketRanges, bestIdx, bestIdx+1, -1, -1) + if len(buckets) == 255 { + break + } + bucketRanges = slices.Replace(bucketRanges, bestIdx, bestIdx+1, bucketRange(split[0]), bucketRange(split[1])) } var paletteRGB []sixelRGB for _, bucket := range buckets { |