Grayscale ASCII color ramp from http://paulbourke.net/dataformats/asciiart/

gfx-ASCII-color-ramp.go

package main

import "github.com/peterhellberg/gfx"

const w, h = 16, 16

const ramp = " .:-=+*#%@"

func main() {
	m := gfx.NewGray(gfx.IR(0, 0, w, h))

	scaler := gfx.NewLinearScaler().
		Range(0, float64(len(ramp)-1)).Domain(0, 255)

	for x := 0; x < w; x++ {
		for y := 0; y < h; y++ {
			m.Set(x, y, gfx.ColorGray(uint8(x*16^y*16)))

			i := int(m.GrayAt(x, y).Y)
			n := int(scaler.ScaleFloat64(float64(i)))
			s := string(ramp[n])

			gfx.Printf("%s%s", s, s)
		}
		gfx.Printf("\n")
	}

	gfx.SavePNG("/tmp/gfx-ASCII-color-ramp.png", gfx.NewScaledImage(m, 32))
}