func colorAlterer(f pixelAlterer) utils.Composable {
return func(c color.Color) color.Color {
r, g, b, a := utils.NormalisedRGBA(c)
grey := uint8(f(r, g, b))
return color.NRGBA{grey, grey, grey, uint8(a)}
}
}
func cropToValue(img image.Image, in func(x, y int) float64) image.Image {
b := img.Bounds()
o := image.NewRGBA(b)
leastX := b.Max.X
leastY := b.Max.Y
mostX := 0
mostY := 0
for y := b.Min.Y; y <= b.Max.Y; y++ {
for x := b.Min.X; x <= b.Max.X; x++ {
if in(x, y) > 0 {
if x < leastX {
leastX = x
}
if y < leastY {
leastY = y
}
if x > mostX {
mostX = x
}
if y > mostY {
mostY = y
}
r, g, b, a := utils.NormalisedRGBA(img.At(x, y))
o.Set(x, y, color.NRGBA{
uint8(r),
uint8(g),
uint8(b),
uint8(float64(a) * in(x, y)),
})
}
}
}
return o.SubImage(image.Rect(leastX, leastY, mostX, mostY))
}
func (_ blueCh) Set(c color.Color, v float64) color.Color {
r, g, _, a := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(r), uint8(g), uint8(v), uint8(a)}
}
func (_ redCh) Set(c color.Color, v float64) color.Color {
_, g, b, a := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(v), uint8(g), uint8(b), uint8(a)}
}
func (_ alphaCh) Set(c color.Color, v float64) color.Color {
r, g, b, _ := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(v)}
}