Move icon generation into dedicated files

icons/ghicons.go

@@ -0,0 +1,107 @@
+package icons
+
+import (
+	"image"
+	"image/color"
+)
+
+type GhIconGenerator struct {
+}
+
+// Based on https://github.com/dgraham/identicon
+func (generator *GhIconGenerator) GenIcon(id string, size int, f func([16]byte) color.RGBA) *image.NRGBA {
+	if size > 512 {
+		size = 512
+	}
+	blocks := 5
+
+	hash := HashBytes(id)
+	nibbles := nibbles(hash)
+	data := make([]bool, blocks*blocks)
+
+	for x := 0; x < blocks; x++ {
+		for y := 0; y < blocks; y++ {
+			ni := x + blocks*(blocks-y-1)
+			if x+blocks*y > 2*blocks {
+				di := (x + blocks*y) - 2*blocks
+				data[di] = nibbles[ni%32]%2 == 0
+			}
+		}
+	}
+
+	return drawImage(mirrorData(data, blocks), blocks, size, f(hash))
+}
+
+// https://processing.org/reference/map_.html
+func remap(value uint32, vmin uint32, vmax uint32, dmin uint32, dmax uint32) float32 {
+	return float32((value-vmin)*(dmax-dmin)) / float32((vmax-vmin)+dmin)
+}
+
+func nibbles(hash [16]byte) []byte {
+	nibbles := make([]byte, 32)
+
+	for i := 0; i <= 15; i++ {
+		nibbles[i*2+1] = hash[i] & 0x0f
+		nibbles[i*2] = hash[i] & 0xf0 >> 4
+	}
+
+	return nibbles
+}
+
+func ColorGh(hash [16]byte) color.RGBA {
+	h1 := (uint16(hash[12]) & 0x0f) << 8
+	h2 := uint16(hash[13])
+
+	h := uint32(h1 | h2)
+	s := uint32(hash[14])
+	l := uint32(hash[15])
+
+	return hslToRgba(
+		remap(h, 0, 4096, 0, 360),
+		65.0-remap(s, 0, 255, 0, 20),
+		75.0-remap(l, 0, 255, 0, 20),
+	)
+}
+
+// http://www.w3.org/TR/css3-color/#hsl-color
+func hslToRgba(hue float32, sat float32, lum float32) color.RGBA {
+	hue = hue / 360.0
+	sat = sat / 100.0
+	lum = lum / 100.0
+
+	t2 := lum + sat - (lum * sat)
+	if lum <= 0.5 {
+		t2 = lum * (sat + 1.0)
+	}
+
+	t1 := lum*2.0 - t2
+
+	return color.RGBA{
+		uint8(hueToRgb(t1, t2, hue+1.0/3.0) * 255),
+		uint8(hueToRgb(t1, t2, hue) * 255),
+		uint8(hueToRgb(t1, t2, hue-1.0/3.0) * 255),
+		0xff,
+	}
+}
+
+func hueToRgb(t1 float32, t2 float32, hue float32) float32 {
+	if hue < 0.0 {
+		hue = hue + 1.0
+	} else if hue >= 1.0 {
+		hue = hue - 1.0
+	}
+
+	if hue < 1.0/6.0 {
+		return t1 + (t2-t1)*6.0*hue
+	}
+
+	if hue < 1.0/2.0 {
+		return t2
+	}
+
+	if hue < 2.0/3.0 {
+		return t1 + (t2-t1)*(2.0/3.0-hue)*6.0
+	}
+
+	return t1
+}