func Auto(img image.Image, ch Channel) image.Image {
var lightest, darkest float64
lightest = 0.0
darkest = 1.0
utils.EachColor(img, func(c color.Color) {
v := ch.Get(c)
if v > lightest {
lightest = v
}
if v < darkest {
darkest = v
}
})
// Use linear stretching algorithm
// v = (v - inLow) * ((outUp - outLow) / (inUp - inLow)) + outLow
return utils.MapColor(img, func(c color.Color) color.Color {
v := ch.Get(c)
v = linearScale(v, darkest, lightest)
return ch.Set(c, v)
})
}
// AutoBlack finds the darkest colour in the image and makes it black, adjusting
// the colours of every other point to achieve the same distribution.
func AutoBlack(img image.Image, ch Channel) image.Image {
var darkest float64 = 1.0
utils.EachColor(img, func(c color.Color) {
v := ch.Get(c)
if v < darkest {
darkest = v
}
})
return SetBlack(img, ch, darkest)
}
func AutoWhite(img image.Image, ch Channel) image.Image {
var lightest float64 = 0.0
utils.EachColor(img, func(c color.Color) {
v := ch.Get(c)
if v > lightest {
lightest = v
}
})
return SetWhite(img, ch, lightest)
}