cmd

cmd/downscale2x/downscale.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"errors"
+	"image"
+	"image/color"
+)
+
+var errOutOfBounds error = errors.New("downscale: out of bounds")
+
+type Downscaled struct {
+	image.Image
+	Factor int
+}
+
+func isOutOfBounds(pt image.Point, img image.Image) bool {
+	x, y := img.Bounds().Dx(), img.Bounds().Dy()
+	if pt.X > x || pt.Y > y {
+		return true
+	}
+	return false
+}
+
+func meanColor(palette color.Palette) color.Color {
+	var r, g, b int
+	for _, v := range palette {
+		c := color.RGBAModel.Convert(v).(color.RGBA)
+		r += int(c.R)
+		g += int(c.G)
+		b += int(c.B)
+	}
+	r, g, b = r/len(palette), g/len(palette), b/len(palette)
+	return color.RGBA{uint8(r), uint8(g), uint8(b), 0xff}
+}
+
+func (d Downscaled) ColorModel() color.Model { return d.Image.ColorModel() }
+func (d Downscaled) Bounds() image.Rectangle {
+	return image.Rect(0, 0, d.Image.Bounds().Dx()/d.Factor, d.Image.Bounds().Dy()/d.Factor)
+}
+func (d Downscaled) At(x, y int) color.Color {
+	palette := color.Palette{}
+	pt := image.Point{x * d.Factor, y * d.Factor}
+	if isOutOfBounds(pt, d.Image) {
+		panic(errOutOfBounds)
+	}
+	for i := 0; i < d.Factor; i++ {
+		for j := 0; j < d.Factor; j++ {
+			currentPt := image.Point{pt.X + i, pt.Y + j}
+			if i > 0 || j > 0 {
+				if isOutOfBounds(currentPt, d.Image) {
+					continue
+				}
+			}
+			palette = append(palette, d.Image.At(currentPt.X, currentPt.Y))
+		}
+	}
+	return palette.Convert(meanColor(palette))
+}