rewrite random noise knowing how bayer works

color_quant.go

@@ -48,15 +48,12 @@ func naivePalette(p color.Palette) quantizerFunction {
 
 // randomNoisePalette injects random noise into the quantization step
 func randomNoisePalette(p color.Palette) quantizerFunction {
+	r := len(p)
 	return func(_, _ int, c color.Color) color.Color {
-		// the randomization here is tuned for the sixteen-color palette for now.
 		// I think the proper theory here is probably "only try and randomize within one palette swatch in either direction".
 		// it might be possible to instead permute the color selected _from the palette_ (i.e. modify the result of p.Index(c))...
 		// ...but I think for that to work you'd need a proper "ordering" for the colors.
-		noise := rand.Intn(64) - 32
-		if noise < 0 {
-			noise = 0
-		}
+		noise := rand.Intn(256) / r
 		rc := permuteColor(c, uint8(noise))
 		return p[p.Index(rc)]
 	}