diff options
| -rw-r--r-- | go.mod | 2 | ||||
| -rw-r--r-- | go.sum | 4 | ||||
| -rw-r--r-- | icat.go | 116 |
3 files changed, 118 insertions, 4 deletions
@@ -4,7 +4,7 @@ go 1.26.3 require ( golang.org/x/image v0.32.0 - roseh.moe/pkg/sixel v0.1.2 + roseh.moe/pkg/sixel v0.2.0 ) require golang.org/x/sys v0.37.0 @@ -2,5 +2,5 @@ golang.org/x/image v0.32.0 h1:6lZQWq75h7L5IWNk0r+SCpUJ6tUVd3v4ZHnbRKLkUDQ= golang.org/x/image v0.32.0/go.mod h1:/R37rrQmKXtO6tYXAjtDLwQgFLHmhW+V6ayXlxzP2Pc= golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ= golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks= -roseh.moe/pkg/sixel v0.1.2 h1:dSRcqJ+sw8g3UdzFyGT+s9IZsWoR/bOBHoNuQh8HfsI= -roseh.moe/pkg/sixel v0.1.2/go.mod h1:DX/c+l3VYm+yXoACY+HXl2gLV5o5iAG6gkHeDddTSrQ= +roseh.moe/pkg/sixel v0.2.0 h1:WkDXFmX7qk40fd870tsSTbFyKW5WUOy7h9FzXu6Q+xY= +roseh.moe/pkg/sixel v0.2.0/go.mod h1:DX/c+l3VYm+yXoACY+HXl2gLV5o5iAG6gkHeDddTSrQ= @@ -6,10 +6,14 @@ import ( "flag" "fmt" "image" + "image/color" _ "image/gif" _ "image/jpeg" _ "image/png" + "math" + "math/rand/v2" "os" + "slices" _ "golang.org/x/image/bmp" "golang.org/x/image/draw" @@ -89,6 +93,116 @@ func load(filename string) (image.Image, error) { return img, nil } +func partition[S ~[]E, E any](a S, i, j, pivotIndex int, cmp func(E, E) int) int { + pivot := a[pivotIndex] + for { + for ; cmp(a[i], pivot) < 0; i++ { + } + for ; cmp(a[j], pivot) > 0; j-- { + } + if i >= j { + return j + } + a[i], a[j] = a[j], a[i] + i++ + j-- + } +} + +func quickSelect[S ~[]E, E any](list S, k int, cmp func(E, E) int) { + left, right := 0, len(list)-1 + for { + if left == right { + return + } + pivotIndex := left + rand.IntN(right-left+1) + pivotIndex = partition(list, left, right, pivotIndex, cmp) + if k <= pivotIndex { + right = pivotIndex + } else { + left = pivotIndex + 1 + } + } +} + +func bucketRange(colors []color.RGBA) color.RGBA { + if len(colors) == 0 { + return color.RGBA{} + } + 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) + } + return color.RGBA{R: maxR - minR, G: maxG - minG, B: maxB - minB} +} + +func cutOnce(colors []color.RGBA, bucketRange color.RGBA) [2][]color.RGBA { + if len(colors) == 0 { + return [...][]color.RGBA{colors, colors} + } + 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) }) + } else if gRange >= rRange && gRange >= bRange { + quickSelect(colors, len(colors)/2, func(x, y color.RGBA) int { return int(x.G) - int(y.G) }) + } else { + quickSelect(colors, len(colors)/2, func(x, y color.RGBA) int { return int(x.B) - int(y.B) }) + } + return [...][]color.RGBA{colors[:len(colors)/2], colors[len(colors)/2:]} +} + +func colorAvg(colors []color.RGBA) color.RGBA { + var r, g, b int64 + for _, c := range colors { + r += int64(c.R) + g += int64(c.G) + b += int64(c.B) + } + n := int64(len(colors)) + return color.RGBA{R: uint8(r / n), G: uint8(g / n), B: uint8(b / n), A: 0xff} +} + +func medianCut(img image.Image) color.Palette { + var colors []color.RGBA + for y := img.Bounds().Min.Y; y < img.Bounds().Max.Y; y++ { + for x := img.Bounds().Min.X; x < img.Bounds().Max.X; x++ { + r, g, b, a := img.At(x, y).RGBA() + if a > 0 { + colors = append(colors, color.RGBA{R: uint8(r >> 8), G: uint8(g >> 8), B: uint8(b >> 8), A: 0xff}) + } + } + } + buckets := [][]color.RGBA{colors} + bucketRanges := []color.RGBA{{}} + for { + var bestRange uint8 + var bestIdx int + for i, rng := range bucketRanges { + r := max(rng.R, rng.G, rng.B) + if r >= bestRange { + bestRange = r + bestIdx = i + } + } + split := cutOnce(buckets[bestIdx], bucketRanges[bestIdx]) + buckets = slices.Replace(buckets, bestIdx, bestIdx+1, split[:]...) + if len(buckets) == 255 { + break + } + bucketRanges = slices.Replace(bucketRanges, bestIdx, bestIdx+1, bucketRange(split[0]), bucketRange(split[1])) + } + palette := color.Palette{color.Transparent} + for _, b := range buckets { + if len(b) > 0 { + palette = append(palette, colorAvg(b)) + } + } + return palette +} + func printImg(img image.Image, x, y, pixelX, pixelY int) error { // Try not to stretch the image. if y == 0 || x != 0 && img.Bounds().Dy()*x <= img.Bounds().Dx()*y*pixelY/pixelX { @@ -106,7 +220,7 @@ func printImg(img image.Image, x, y, pixelX, pixelY int) error { case modeBlock24: sixel.PrintBlock(os.Stdout, dst) case modeSixel: - sixel.Print(os.Stdout, dst) + sixel.Print(os.Stdout, dst, medianCut(dst)) } fmt.Println() return nil |