Turns the alpha channel of images into hue, using basic linear interpolation between color stops.
colorizeAlpha(
// a canvas element with things drawn on it
canvas,
// a list of steps, assumed to be equidistant,
// start at 0% and end at 100%, in [r, g, b] form.
[[255, 0, 0], [255, 255, 0], [0, 255, 0], [0, 255, 255]]);