package main import ( "image" "image/color" ) // Convert to binary image func Transform(src image.Image) image.Image { bounds := src.Bounds() w, h := bounds.Max.X, bounds.Max.Y ret := image.NewRGBA(image.Rectangle{image.Point{0, 0}, image.Point{w, h}}) for x := 0; x < w; x++ { for y := 0; y < h; y++ { _, g, _, _ := src.At(x, y).RGBA() ret.Set(x, y, color.RGBA{0, uint8(g / 256), 0, 0}) } } return ret }