// Lightne selects the lighter of each pixels' colour channels.
func Lighten(a, b image.Image) image.Image {
return BlendPixels(a, b, func(c, d color.Color) color.Color {
i, j, k, l := utils.RatioRGBA(c)
m, n, o, p := utils.RatioRGBA(d)
r := utils.Maxf(i, m)
g := utils.Maxf(j, n)
b := utils.Maxf(k, o)
a := utils.Maxf(l, p)
return ratioNRGBA(r, g, b, a)
})
}
func hsiaModel(c color.Color) color.Color {
if _, ok := c.(HSIA); ok {
return c
}
r, g, b, a := utils.RatioRGBA(c)
maxi := utils.Maxf(r, g, b)
mini := utils.Minf(r, g, b)
chroma := maxi - mini
// Work out hue
hdash := 0.0
if chroma == 0 {
hdash = 0
} else if maxi == r {
hdash = math.Mod((g-b)/chroma, 6)
} else if maxi == g {
hdash = (b-r)/chroma + 2.0
} else if maxi == b {
hdash = (r-g)/chroma + 4.0
}
hue := hdash * 60
if chroma == 0 {
hue = 0
}
// Work out intensity
intensity := (r + g + b) / 3
// Work out saturation
saturation := 0.0
if chroma != 0 {
saturation = 1 - mini/intensity
}
// prefer positive hues
if hue < 0 {
hue += 360
}
return HSIA{hue, saturation, intensity, a}
}
func hslaModel(c color.Color) color.Color {
if _, ok := c.(HSLA); ok {
return c
}
r, g, b, a := utils.RatioRGBA(c)
maxi := utils.Maxf(r, g, b)
mini := utils.Minf(r, g, b)
chroma := maxi - mini
// Work out hue
hdash := 0.0
if chroma == 0 {
hdash = 0
} else if maxi == r {
hdash = math.Mod((g-b)/chroma, 6)
} else if maxi == g {
hdash = (b-r)/chroma + 2.0
} else if maxi == b {
hdash = (r-g)/chroma + 4.0
}
hue := hdash * 60
if chroma == 0 {
hue = 0
}
// Work out lightness
lightness := 0.5 * (maxi + mini)
// Work out saturation
saturation := 0.0
if chroma != 0 {
saturation = chroma / (1 - math.Abs(2*lightness-1))
}
return HSLA{hue, saturation, lightness, a}
}
func hsvaModel(c color.Color) color.Color {
if _, ok := c.(HSVA); ok {
return c
}
r, g, b, a := utils.RatioRGBA(c)
maxi := utils.Maxf(r, g, b)
mini := utils.Minf(r, g, b)
chroma := maxi - mini
// Work out hue
hdash := 0.0
if chroma == 0 {
hdash = 0
} else if maxi == r {
hdash = math.Mod((g-b)/chroma, 6)
} else if maxi == g {
hdash = (b-r)/chroma + 2.0
} else if maxi == b {
hdash = (r-g)/chroma + 4.0
}
hue := hdash * 60
if chroma == 0 {
hue = 0
}
// Work out value
value := maxi
// Work out saturation
saturation := 0.0
if chroma != 0 {
saturation = chroma / value
}
return HSVA{hue, saturation, value, a}
}