diff options
Diffstat (limited to 'convert.go')
| -rw-r--r-- | convert.go | 148 |
1 files changed, 2 insertions, 146 deletions
@@ -5,13 +5,10 @@ import ( "flag" "fmt" "image" - "image/color" "image/gif" "image/jpeg" "image/png" - "math" "os" - "slices" "strings" "golang.org/x/image/bmp" @@ -46,151 +43,10 @@ func load(filename string) (image.Image, error) { return img, nil } -func divRound[N ~int | ~int64](n, d N) N { +func divRound(n, d int) int { return (n + d/2) / d } -func sign(n int) float64 { - if n < 0 { - return -1 - } - if n > 0 { - return 1 - } - return 0 -} - -func floydRivest[S ~[]E, E any](array S, left, right, k int, cmp func(E, E) int) { - for right > left { - if right-left > 600 { - n := right - left + 1 - i := k - left + 1 - z := math.Log(float64(n)) - s := .5 * math.Exp(2*z/3) - sd := .5 * math.Sqrt(z*s*(float64(n)-s)/float64(n)) * sign(i-n/2) - newLeft := max(left, int(float64(k)-float64(i)*s/float64(n)+sd)) - newRight := min(right, int(float64(k)+float64(n-i)*s/float64(n)+sd)) - floydRivest(array, newLeft, newRight, k, cmp) - } - t := array[k] - i := left - j := right - array[left], array[k] = array[k], array[left] - if cmp(array[right], t) > 0 { - array[right], array[left] = array[left], array[right] - } - for i < j { - array[i], array[j] = array[j], array[i] - i++ - j-- - for ; cmp(array[i], t) < 0; i++ { - } - for ; cmp(array[j], t) > 0; j-- { - } - } - if cmp(array[left], t) == 0 { - array[left], array[j] = array[j], array[left] - } else { - j++ - array[j], array[right] = array[right], array[j] - } - if j <= k { - left = j + 1 - } - if k <= j { - right = j - 1 - } - } -} - -func quickSelect[S ~[]E, E any](list S, k int, cmp func(E, E) int) { - floydRivest(list, 0, len(list)-1, k, cmp) -} - -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(divRound(r, n)), G: uint8(divRound(g, n)), B: uint8(divRound(b, n)), A: 0xff} -} - -func medianCut(palette color.Palette, img image.Image, n int) 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) == n-1 { - break - } - bucketRanges = slices.Replace(bucketRanges, bestIdx, bestIdx+1, bucketRange(split[0]), bucketRange(split[1])) - } - palette = append(palette, color.Transparent) - for _, b := range buckets { - if len(b) > 0 { - palette = append(palette, colorAvg(b)) - } - } - return palette -} - -type medianCutQuantizer struct{} - -func (medianCutQuantizer) Quantize(p color.Palette, m image.Image) color.Palette { - return medianCut(p, m, cap(p)-len(p)) -} - func resize(img image.Image) image.Image { x, y := *x, *y if x == 0 { @@ -255,7 +111,7 @@ func run() error { defer outputFile.Close() switch ext { case "gif": - err = gif.Encode(outputFile, input, &gif.Options{Quantizer: medianCutQuantizer{}}) + err = gif.Encode(outputFile, input, nil) case "jpeg", "jpg": err = jpeg.Encode(outputFile, input, &jpeg.Options{Quality: 100}) case "png": |