diff options
Diffstat (limited to 'sixel.go')
| -rw-r--r-- | sixel.go | 81 |
1 files changed, 45 insertions, 36 deletions
@@ -11,6 +11,7 @@ import ( "image/draw" "io" "maps" + "math" "slices" ) @@ -30,33 +31,38 @@ func (c sixelRGB) RGBA() (r, g, b, a uint32) { return scaleFFFF(c.r), scaleFFFF(c.g), scaleFFFF(c.b), 0xffff } -func cutOnce(colors []color.RGBA) [2][]color.RGBA { - var minR, maxR, minG, maxG, minB, maxB uint8 +func bucketRange(colors []color.RGBA) (rRange, gRange, bRange uint8) { + if len(colors) == 0 { + return 0, 0, 0 + } + var minR, minG, minB uint8 = math.MaxUint8, math.MaxUint8, math.MaxUint8 + var maxR, maxG, maxB uint8 for _, c := range colors { minR, maxR = min(minR, c.R), max(maxR, c.R) 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 + return maxR - minR, maxG - minG, maxB - minB +} + +func cutOnce(colors []color.RGBA) [2][]color.RGBA { + rRange, gRange, bRange := bucketRange(colors) if rRange >= gRange && rRange >= bRange { - slices.SortFunc(colors, func(x, y color.RGBA) int { return cmp.Compare(x.R, y.R) }) + slices.SortFunc(colors, func(x, y color.RGBA) int { + return cmp.Or(cmp.Compare(x.R, y.R), cmp.Compare(x.G, y.G), cmp.Compare(x.B, y.B)) + }) } else if gRange >= rRange && gRange >= bRange { - slices.SortFunc(colors, func(x, y color.RGBA) int { return cmp.Compare(x.G, y.G) }) + slices.SortFunc(colors, func(x, y color.RGBA) int { + return cmp.Or(cmp.Compare(x.G, y.G), cmp.Compare(x.R, y.R), cmp.Compare(x.B, y.B)) + }) } else { - slices.SortFunc(colors, func(x, y color.RGBA) int { return cmp.Compare(x.B, y.B) }) + slices.SortFunc(colors, func(x, y color.RGBA) int { + return cmp.Or(cmp.Compare(x.B, y.B), cmp.Compare(x.R, y.R), cmp.Compare(x.G, y.G)) + }) } return [...][]color.RGBA{colors[:len(colors)/2], colors[len(colors)/2:]} } -func cutDepth(colors []color.RGBA, depth int) [][]color.RGBA { - split := cutOnce(colors) - depth++ - if depth == 8 { - return split[:] - } - return append(cutDepth(split[0], depth), cutDepth(split[1], depth)...) -} - func colorAvg(colors []color.RGBA) sixelRGB { var r, g, b int64 for _, c := range colors { @@ -65,19 +71,7 @@ func colorAvg(colors []color.RGBA) sixelRGB { b += int64(c.B) } n := int64(len(colors)) - c := sixelRGB{r: scale100(r / n), g: scale100(g / n), b: scale100(b / n)} - return c -} - -func avgPaletteRGB(buckets [][]color.RGBA) []sixelRGB { - paletteRGB := make([]sixelRGB, len(buckets)) - for i, bucket := range buckets { - paletteRGB[i] = colorAvg(bucket) - } - slices.SortFunc(paletteRGB, func(x, y sixelRGB) int { - return cmp.Or(cmp.Compare(x.r, y.r), cmp.Compare(x.g, y.g), cmp.Compare(x.b, y.b)) - }) - return slices.Compact(paletteRGB) + return sixelRGB{r: scale100(r / n), g: scale100(g / n), b: scale100(b / n)} } func medianCut(img image.Image) color.Palette { @@ -90,15 +84,30 @@ func medianCut(img image.Image) color.Palette { } } } - buckets := slices.DeleteFunc(cutDepth(colors, 0), func(b []color.RGBA) bool { return len(b) == 0 }) - paletteRGB := avgPaletteRGB(buckets) - if len(paletteRGB) == 256 { - lastBucket := buckets[len(buckets)-1] - secondLastBucket := buckets[len(buckets)-2] - buckets[len(buckets)-2] = secondLastBucket[:len(secondLastBucket)+len(lastBucket)] - buckets = buckets[:len(buckets)-1] - paletteRGB = avgPaletteRGB(buckets) + buckets := [][]color.RGBA{colors} + for len(buckets) < 255 { + var bestRange uint8 + var bestIdx int + for i, b := range buckets { + r := max(bucketRange(b)) + if r >= bestRange { + bestRange = r + bestIdx = i + } + } + split := cutOnce(buckets[bestIdx]) + buckets = slices.Replace(buckets, bestIdx, bestIdx+1, split[:]...) + } + var paletteRGB []sixelRGB + for _, bucket := range buckets { + if len(bucket) > 0 { + paletteRGB = append(paletteRGB, colorAvg(bucket)) + } } + slices.SortFunc(paletteRGB, func(x, y sixelRGB) int { + return cmp.Or(cmp.Compare(x.r, y.r), cmp.Compare(x.g, y.g), cmp.Compare(x.b, y.b)) + }) + paletteRGB = slices.Compact(paletteRGB) palette := slices.Grow(color.Palette{color.Transparent}, len(paletteRGB)) for _, c := range paletteRGB { palette = append(palette, c) |