904 lines
24 KiB
Go
904 lines
24 KiB
Go
// The colorful package provides all kinds of functions for working with colors.
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package colorful
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import (
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"fmt"
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"image/color"
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"math"
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)
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// A color is stored internally using sRGB (standard RGB) values in the range 0-1
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type Color struct {
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R, G, B float64
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}
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// Implement the Go color.Color interface.
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func (col Color) RGBA() (r, g, b, a uint32) {
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r = uint32(col.R*65535.0 + 0.5)
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g = uint32(col.G*65535.0 + 0.5)
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b = uint32(col.B*65535.0 + 0.5)
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a = 0xFFFF
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return
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}
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// Constructs a colorful.Color from something implementing color.Color
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func MakeColor(col color.Color) (Color, bool) {
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r, g, b, a := col.RGBA()
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if a == 0 {
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return Color{0, 0, 0}, false
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}
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// Since color.Color is alpha pre-multiplied, we need to divide the
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// RGB values by alpha again in order to get back the original RGB.
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r *= 0xffff
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r /= a
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g *= 0xffff
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g /= a
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b *= 0xffff
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b /= a
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return Color{float64(r) / 65535.0, float64(g) / 65535.0, float64(b) / 65535.0}, true
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}
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// Might come in handy sometimes to reduce boilerplate code.
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func (col Color) RGB255() (r, g, b uint8) {
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r = uint8(col.R*255.0 + 0.5)
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g = uint8(col.G*255.0 + 0.5)
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b = uint8(col.B*255.0 + 0.5)
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return
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}
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// This is the tolerance used when comparing colors using AlmostEqualRgb.
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const Delta = 1.0 / 255.0
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// This is the default reference white point.
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var D65 = [3]float64{0.95047, 1.00000, 1.08883}
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// And another one.
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var D50 = [3]float64{0.96422, 1.00000, 0.82521}
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// Checks whether the color exists in RGB space, i.e. all values are in [0..1]
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func (c Color) IsValid() bool {
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return 0.0 <= c.R && c.R <= 1.0 &&
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0.0 <= c.G && c.G <= 1.0 &&
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0.0 <= c.B && c.B <= 1.0
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}
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func clamp01(v float64) float64 {
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return math.Max(0.0, math.Min(v, 1.0))
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}
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// Returns Clamps the color into valid range, clamping each value to [0..1]
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// If the color is valid already, this is a no-op.
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func (c Color) Clamped() Color {
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return Color{clamp01(c.R), clamp01(c.G), clamp01(c.B)}
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}
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func sq(v float64) float64 {
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return v * v
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}
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func cub(v float64) float64 {
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return v * v * v
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}
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// DistanceRgb computes the distance between two colors in RGB space.
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// This is not a good measure! Rather do it in Lab space.
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func (c1 Color) DistanceRgb(c2 Color) float64 {
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return math.Sqrt(sq(c1.R-c2.R) + sq(c1.G-c2.G) + sq(c1.B-c2.B))
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}
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// Check for equality between colors within the tolerance Delta (1/255).
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func (c1 Color) AlmostEqualRgb(c2 Color) bool {
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return math.Abs(c1.R-c2.R)+
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math.Abs(c1.G-c2.G)+
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math.Abs(c1.B-c2.B) < 3.0*Delta
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}
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// You don't really want to use this, do you? Go for BlendLab, BlendLuv or BlendHcl.
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func (c1 Color) BlendRgb(c2 Color, t float64) Color {
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return Color{c1.R + t*(c2.R-c1.R),
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c1.G + t*(c2.G-c1.G),
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c1.B + t*(c2.B-c1.B)}
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}
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// Utility used by Hxx color-spaces for interpolating between two angles in [0,360].
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func interp_angle(a0, a1, t float64) float64 {
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// Based on the answer here: http://stackoverflow.com/a/14498790/2366315
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// With potential proof that it works here: http://math.stackexchange.com/a/2144499
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delta := math.Mod(math.Mod(a1-a0, 360.0)+540, 360.0) - 180.0
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return math.Mod(a0+t*delta+360.0, 360.0)
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}
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/// HSV ///
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///////////
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// From http://en.wikipedia.org/wiki/HSL_and_HSV
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// Note that h is in [0..360] and s,v in [0..1]
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// Hsv returns the Hue [0..360], Saturation and Value [0..1] of the color.
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func (col Color) Hsv() (h, s, v float64) {
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min := math.Min(math.Min(col.R, col.G), col.B)
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v = math.Max(math.Max(col.R, col.G), col.B)
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C := v - min
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s = 0.0
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if v != 0.0 {
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s = C / v
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}
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h = 0.0 // We use 0 instead of undefined as in wp.
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if min != v {
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if v == col.R {
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h = math.Mod((col.G-col.B)/C, 6.0)
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}
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if v == col.G {
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h = (col.B-col.R)/C + 2.0
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}
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if v == col.B {
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h = (col.R-col.G)/C + 4.0
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}
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h *= 60.0
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if h < 0.0 {
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h += 360.0
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}
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}
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return
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}
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// Hsv creates a new Color given a Hue in [0..360], a Saturation and a Value in [0..1]
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func Hsv(H, S, V float64) Color {
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Hp := H / 60.0
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C := V * S
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X := C * (1.0 - math.Abs(math.Mod(Hp, 2.0)-1.0))
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m := V - C
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r, g, b := 0.0, 0.0, 0.0
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switch {
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case 0.0 <= Hp && Hp < 1.0:
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r = C
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g = X
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case 1.0 <= Hp && Hp < 2.0:
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r = X
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g = C
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case 2.0 <= Hp && Hp < 3.0:
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g = C
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b = X
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case 3.0 <= Hp && Hp < 4.0:
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g = X
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b = C
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case 4.0 <= Hp && Hp < 5.0:
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r = X
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b = C
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case 5.0 <= Hp && Hp < 6.0:
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r = C
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b = X
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}
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return Color{m + r, m + g, m + b}
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}
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// You don't really want to use this, do you? Go for BlendLab, BlendLuv or BlendHcl.
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func (c1 Color) BlendHsv(c2 Color, t float64) Color {
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h1, s1, v1 := c1.Hsv()
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h2, s2, v2 := c2.Hsv()
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// We know that h are both in [0..360]
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return Hsv(interp_angle(h1, h2, t), s1+t*(s2-s1), v1+t*(v2-v1))
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}
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/// HSL ///
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///////////
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// Hsl returns the Hue [0..360], Saturation [0..1], and Luminance (lightness) [0..1] of the color.
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func (col Color) Hsl() (h, s, l float64) {
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min := math.Min(math.Min(col.R, col.G), col.B)
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max := math.Max(math.Max(col.R, col.G), col.B)
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l = (max + min) / 2
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if min == max {
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s = 0
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h = 0
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} else {
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if l < 0.5 {
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s = (max - min) / (max + min)
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} else {
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s = (max - min) / (2.0 - max - min)
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}
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if max == col.R {
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h = (col.G - col.B) / (max - min)
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} else if max == col.G {
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h = 2.0 + (col.B-col.R)/(max-min)
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} else {
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h = 4.0 + (col.R-col.G)/(max-min)
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}
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h *= 60
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if h < 0 {
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h += 360
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}
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}
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return
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}
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// Hsl creates a new Color given a Hue in [0..360], a Saturation [0..1], and a Luminance (lightness) in [0..1]
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func Hsl(h, s, l float64) Color {
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if s == 0 {
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return Color{l, l, l}
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}
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var r, g, b float64
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var t1 float64
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var t2 float64
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var tr float64
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var tg float64
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var tb float64
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if l < 0.5 {
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t1 = l * (1.0 + s)
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} else {
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t1 = l + s - l*s
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}
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t2 = 2*l - t1
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h = h / 360
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tr = h + 1.0/3.0
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tg = h
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tb = h - 1.0/3.0
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if tr < 0 {
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tr++
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}
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if tr > 1 {
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tr--
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}
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if tg < 0 {
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tg++
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}
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if tg > 1 {
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tg--
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}
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if tb < 0 {
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tb++
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}
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if tb > 1 {
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tb--
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}
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// Red
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if 6*tr < 1 {
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r = t2 + (t1-t2)*6*tr
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} else if 2*tr < 1 {
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r = t1
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} else if 3*tr < 2 {
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r = t2 + (t1-t2)*(2.0/3.0-tr)*6
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} else {
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r = t2
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}
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// Green
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if 6*tg < 1 {
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g = t2 + (t1-t2)*6*tg
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} else if 2*tg < 1 {
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g = t1
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} else if 3*tg < 2 {
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g = t2 + (t1-t2)*(2.0/3.0-tg)*6
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} else {
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g = t2
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}
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// Blue
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if 6*tb < 1 {
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b = t2 + (t1-t2)*6*tb
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} else if 2*tb < 1 {
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b = t1
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} else if 3*tb < 2 {
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b = t2 + (t1-t2)*(2.0/3.0-tb)*6
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} else {
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b = t2
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}
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return Color{r, g, b}
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}
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/// Hex ///
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///////////
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// Hex returns the hex "html" representation of the color, as in #ff0080.
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func (col Color) Hex() string {
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// Add 0.5 for rounding
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return fmt.Sprintf("#%02x%02x%02x", uint8(col.R*255.0+0.5), uint8(col.G*255.0+0.5), uint8(col.B*255.0+0.5))
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}
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// Hex parses a "html" hex color-string, either in the 3 "#f0c" or 6 "#ff1034" digits form.
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func Hex(scol string) (Color, error) {
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format := "#%02x%02x%02x"
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factor := 1.0 / 255.0
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if len(scol) == 4 {
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format = "#%1x%1x%1x"
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factor = 1.0 / 15.0
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}
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var r, g, b uint8
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n, err := fmt.Sscanf(scol, format, &r, &g, &b)
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if err != nil {
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return Color{}, err
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}
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if n != 3 {
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return Color{}, fmt.Errorf("color: %v is not a hex-color", scol)
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}
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return Color{float64(r) * factor, float64(g) * factor, float64(b) * factor}, nil
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}
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/// Linear ///
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//////////////
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// http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/
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// http://www.brucelindbloom.com/Eqn_RGB_to_XYZ.html
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func linearize(v float64) float64 {
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if v <= 0.04045 {
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return v / 12.92
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}
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return math.Pow((v+0.055)/1.055, 2.4)
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}
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// LinearRgb converts the color into the linear RGB space (see http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/).
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func (col Color) LinearRgb() (r, g, b float64) {
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r = linearize(col.R)
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g = linearize(col.G)
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b = linearize(col.B)
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return
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}
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// A much faster and still quite precise linearization using a 6th-order Taylor approximation.
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// See the accompanying Jupyter notebook for derivation of the constants.
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func linearize_fast(v float64) float64 {
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v1 := v - 0.5
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v2 := v1 * v1
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v3 := v2 * v1
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v4 := v2 * v2
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//v5 := v3*v2
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return -0.248750514614486 + 0.925583310193438*v + 1.16740237321695*v2 + 0.280457026598666*v3 - 0.0757991963780179*v4 //+ 0.0437040411548932*v5
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}
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// FastLinearRgb is much faster than and almost as accurate as LinearRgb.
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// BUT it is important to NOTE that they only produce good results for valid colors r,g,b in [0,1].
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func (col Color) FastLinearRgb() (r, g, b float64) {
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r = linearize_fast(col.R)
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g = linearize_fast(col.G)
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b = linearize_fast(col.B)
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return
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}
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func delinearize(v float64) float64 {
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if v <= 0.0031308 {
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return 12.92 * v
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}
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return 1.055*math.Pow(v, 1.0/2.4) - 0.055
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}
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// LinearRgb creates an sRGB color out of the given linear RGB color (see http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/).
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func LinearRgb(r, g, b float64) Color {
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return Color{delinearize(r), delinearize(g), delinearize(b)}
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}
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func delinearize_fast(v float64) float64 {
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// This function (fractional root) is much harder to linearize, so we need to split.
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if v > 0.2 {
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v1 := v - 0.6
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v2 := v1 * v1
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v3 := v2 * v1
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v4 := v2 * v2
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v5 := v3 * v2
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return 0.442430344268235 + 0.592178981271708*v - 0.287864782562636*v2 + 0.253214392068985*v3 - 0.272557158129811*v4 + 0.325554383321718*v5
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} else if v > 0.03 {
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v1 := v - 0.115
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v2 := v1 * v1
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v3 := v2 * v1
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v4 := v2 * v2
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v5 := v3 * v2
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return 0.194915592891669 + 1.55227076330229*v - 3.93691860257828*v2 + 18.0679839248761*v3 - 101.468750302746*v4 + 632.341487393927*v5
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} else {
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v1 := v - 0.015
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v2 := v1 * v1
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v3 := v2 * v1
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v4 := v2 * v2
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v5 := v3 * v2
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// You can clearly see from the involved constants that the low-end is highly nonlinear.
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return 0.0519565234928877 + 5.09316778537561*v - 99.0338180489702*v2 + 3484.52322764895*v3 - 150028.083412663*v4 + 7168008.42971613*v5
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}
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}
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// FastLinearRgb is much faster than and almost as accurate as LinearRgb.
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// BUT it is important to NOTE that they only produce good results for valid inputs r,g,b in [0,1].
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func FastLinearRgb(r, g, b float64) Color {
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return Color{delinearize_fast(r), delinearize_fast(g), delinearize_fast(b)}
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}
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// XyzToLinearRgb converts from CIE XYZ-space to Linear RGB space.
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func XyzToLinearRgb(x, y, z float64) (r, g, b float64) {
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r = 3.2404542*x - 1.5371385*y - 0.4985314*z
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g = -0.9692660*x + 1.8760108*y + 0.0415560*z
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b = 0.0556434*x - 0.2040259*y + 1.0572252*z
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return
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}
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func LinearRgbToXyz(r, g, b float64) (x, y, z float64) {
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x = 0.4124564*r + 0.3575761*g + 0.1804375*b
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y = 0.2126729*r + 0.7151522*g + 0.0721750*b
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z = 0.0193339*r + 0.1191920*g + 0.9503041*b
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return
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}
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/// XYZ ///
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///////////
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// http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/
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func (col Color) Xyz() (x, y, z float64) {
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return LinearRgbToXyz(col.LinearRgb())
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}
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func Xyz(x, y, z float64) Color {
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return LinearRgb(XyzToLinearRgb(x, y, z))
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}
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/// xyY ///
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///////////
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// http://www.brucelindbloom.com/Eqn_XYZ_to_xyY.html
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// Well, the name is bad, since it's xyY but Golang needs me to start with a
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// capital letter to make the method public.
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func XyzToXyy(X, Y, Z float64) (x, y, Yout float64) {
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return XyzToXyyWhiteRef(X, Y, Z, D65)
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}
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func XyzToXyyWhiteRef(X, Y, Z float64, wref [3]float64) (x, y, Yout float64) {
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Yout = Y
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N := X + Y + Z
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if math.Abs(N) < 1e-14 {
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// When we have black, Bruce Lindbloom recommends to use
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// the reference white's chromacity for x and y.
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x = wref[0] / (wref[0] + wref[1] + wref[2])
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y = wref[1] / (wref[0] + wref[1] + wref[2])
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} else {
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x = X / N
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y = Y / N
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}
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return
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}
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func XyyToXyz(x, y, Y float64) (X, Yout, Z float64) {
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Yout = Y
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|
|
if -1e-14 < y && y < 1e-14 {
|
|
X = 0.0
|
|
Z = 0.0
|
|
} else {
|
|
X = Y / y * x
|
|
Z = Y / y * (1.0 - x - y)
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
// Converts the given color to CIE xyY space using D65 as reference white.
|
|
// (Note that the reference white is only used for black input.)
|
|
// x, y and Y are in [0..1]
|
|
func (col Color) Xyy() (x, y, Y float64) {
|
|
return XyzToXyy(col.Xyz())
|
|
}
|
|
|
|
// Converts the given color to CIE xyY space, taking into account
|
|
// a given reference white. (i.e. the monitor's white)
|
|
// (Note that the reference white is only used for black input.)
|
|
// x, y and Y are in [0..1]
|
|
func (col Color) XyyWhiteRef(wref [3]float64) (x, y, Y float64) {
|
|
X, Y2, Z := col.Xyz()
|
|
return XyzToXyyWhiteRef(X, Y2, Z, wref)
|
|
}
|
|
|
|
// Generates a color by using data given in CIE xyY space.
|
|
// x, y and Y are in [0..1]
|
|
func Xyy(x, y, Y float64) Color {
|
|
return Xyz(XyyToXyz(x, y, Y))
|
|
}
|
|
|
|
/// L*a*b* ///
|
|
//////////////
|
|
// http://en.wikipedia.org/wiki/Lab_color_space#CIELAB-CIEXYZ_conversions
|
|
// For L*a*b*, we need to L*a*b*<->XYZ->RGB and the first one is device dependent.
|
|
|
|
func lab_f(t float64) float64 {
|
|
if t > 6.0/29.0*6.0/29.0*6.0/29.0 {
|
|
return math.Cbrt(t)
|
|
}
|
|
return t/3.0*29.0/6.0*29.0/6.0 + 4.0/29.0
|
|
}
|
|
|
|
func XyzToLab(x, y, z float64) (l, a, b float64) {
|
|
// Use D65 white as reference point by default.
|
|
// http://www.fredmiranda.com/forum/topic/1035332
|
|
// http://en.wikipedia.org/wiki/Standard_illuminant
|
|
return XyzToLabWhiteRef(x, y, z, D65)
|
|
}
|
|
|
|
func XyzToLabWhiteRef(x, y, z float64, wref [3]float64) (l, a, b float64) {
|
|
fy := lab_f(y / wref[1])
|
|
l = 1.16*fy - 0.16
|
|
a = 5.0 * (lab_f(x/wref[0]) - fy)
|
|
b = 2.0 * (fy - lab_f(z/wref[2]))
|
|
return
|
|
}
|
|
|
|
func lab_finv(t float64) float64 {
|
|
if t > 6.0/29.0 {
|
|
return t * t * t
|
|
}
|
|
return 3.0 * 6.0 / 29.0 * 6.0 / 29.0 * (t - 4.0/29.0)
|
|
}
|
|
|
|
func LabToXyz(l, a, b float64) (x, y, z float64) {
|
|
// D65 white (see above).
|
|
return LabToXyzWhiteRef(l, a, b, D65)
|
|
}
|
|
|
|
func LabToXyzWhiteRef(l, a, b float64, wref [3]float64) (x, y, z float64) {
|
|
l2 := (l + 0.16) / 1.16
|
|
x = wref[0] * lab_finv(l2+a/5.0)
|
|
y = wref[1] * lab_finv(l2)
|
|
z = wref[2] * lab_finv(l2-b/2.0)
|
|
return
|
|
}
|
|
|
|
// Converts the given color to CIE L*a*b* space using D65 as reference white.
|
|
func (col Color) Lab() (l, a, b float64) {
|
|
return XyzToLab(col.Xyz())
|
|
}
|
|
|
|
// Converts the given color to CIE L*a*b* space, taking into account
|
|
// a given reference white. (i.e. the monitor's white)
|
|
func (col Color) LabWhiteRef(wref [3]float64) (l, a, b float64) {
|
|
x, y, z := col.Xyz()
|
|
return XyzToLabWhiteRef(x, y, z, wref)
|
|
}
|
|
|
|
// Generates a color by using data given in CIE L*a*b* space using D65 as reference white.
|
|
// WARNING: many combinations of `l`, `a`, and `b` values do not have corresponding
|
|
// valid RGB values, check the FAQ in the README if you're unsure.
|
|
func Lab(l, a, b float64) Color {
|
|
return Xyz(LabToXyz(l, a, b))
|
|
}
|
|
|
|
// Generates a color by using data given in CIE L*a*b* space, taking
|
|
// into account a given reference white. (i.e. the monitor's white)
|
|
func LabWhiteRef(l, a, b float64, wref [3]float64) Color {
|
|
return Xyz(LabToXyzWhiteRef(l, a, b, wref))
|
|
}
|
|
|
|
// DistanceLab is a good measure of visual similarity between two colors!
|
|
// A result of 0 would mean identical colors, while a result of 1 or higher
|
|
// means the colors differ a lot.
|
|
func (c1 Color) DistanceLab(c2 Color) float64 {
|
|
l1, a1, b1 := c1.Lab()
|
|
l2, a2, b2 := c2.Lab()
|
|
return math.Sqrt(sq(l1-l2) + sq(a1-a2) + sq(b1-b2))
|
|
}
|
|
|
|
// That's actually the same, but I don't want to break code.
|
|
func (c1 Color) DistanceCIE76(c2 Color) float64 {
|
|
return c1.DistanceLab(c2)
|
|
}
|
|
|
|
// Uses the CIE94 formula to calculate color distance. More accurate than
|
|
// DistanceLab, but also more work.
|
|
func (cl Color) DistanceCIE94(cr Color) float64 {
|
|
l1, a1, b1 := cl.Lab()
|
|
l2, a2, b2 := cr.Lab()
|
|
|
|
// NOTE: Since all those formulas expect L,a,b values 100x larger than we
|
|
// have them in this library, we either need to adjust all constants
|
|
// in the formula, or convert the ranges of L,a,b before, and then
|
|
// scale the distances down again. The latter is less error-prone.
|
|
l1, a1, b1 = l1*100.0, a1*100.0, b1*100.0
|
|
l2, a2, b2 = l2*100.0, a2*100.0, b2*100.0
|
|
|
|
kl := 1.0 // 2.0 for textiles
|
|
kc := 1.0
|
|
kh := 1.0
|
|
k1 := 0.045 // 0.048 for textiles
|
|
k2 := 0.015 // 0.014 for textiles.
|
|
|
|
deltaL := l1 - l2
|
|
c1 := math.Sqrt(sq(a1) + sq(b1))
|
|
c2 := math.Sqrt(sq(a2) + sq(b2))
|
|
deltaCab := c1 - c2
|
|
|
|
// Not taking Sqrt here for stability, and it's unnecessary.
|
|
deltaHab2 := sq(a1-a2) + sq(b1-b2) - sq(deltaCab)
|
|
sl := 1.0
|
|
sc := 1.0 + k1*c1
|
|
sh := 1.0 + k2*c1
|
|
|
|
vL2 := sq(deltaL / (kl * sl))
|
|
vC2 := sq(deltaCab / (kc * sc))
|
|
vH2 := deltaHab2 / sq(kh*sh)
|
|
|
|
return math.Sqrt(vL2+vC2+vH2) * 0.01 // See above.
|
|
}
|
|
|
|
// DistanceCIEDE2000 uses the Delta E 2000 formula to calculate color
|
|
// distance. It is more expensive but more accurate than both DistanceLab
|
|
// and DistanceCIE94.
|
|
func (cl Color) DistanceCIEDE2000(cr Color) float64 {
|
|
return cl.DistanceCIEDE2000klch(cr, 1.0, 1.0, 1.0)
|
|
}
|
|
|
|
// DistanceCIEDE2000klch uses the Delta E 2000 formula with custom values
|
|
// for the weighting factors kL, kC, and kH.
|
|
func (cl Color) DistanceCIEDE2000klch(cr Color, kl, kc, kh float64) float64 {
|
|
l1, a1, b1 := cl.Lab()
|
|
l2, a2, b2 := cr.Lab()
|
|
|
|
// As with CIE94, we scale up the ranges of L,a,b beforehand and scale
|
|
// them down again afterwards.
|
|
l1, a1, b1 = l1*100.0, a1*100.0, b1*100.0
|
|
l2, a2, b2 = l2*100.0, a2*100.0, b2*100.0
|
|
|
|
cab1 := math.Sqrt(sq(a1) + sq(b1))
|
|
cab2 := math.Sqrt(sq(a2) + sq(b2))
|
|
cabmean := (cab1 + cab2) / 2
|
|
|
|
g := 0.5 * (1 - math.Sqrt(math.Pow(cabmean, 7)/(math.Pow(cabmean, 7)+math.Pow(25, 7))))
|
|
ap1 := (1 + g) * a1
|
|
ap2 := (1 + g) * a2
|
|
cp1 := math.Sqrt(sq(ap1) + sq(b1))
|
|
cp2 := math.Sqrt(sq(ap2) + sq(b2))
|
|
|
|
hp1 := 0.0
|
|
if b1 != ap1 || ap1 != 0 {
|
|
hp1 = math.Atan2(b1, ap1)
|
|
if hp1 < 0 {
|
|
hp1 += math.Pi * 2
|
|
}
|
|
hp1 *= 180 / math.Pi
|
|
}
|
|
hp2 := 0.0
|
|
if b2 != ap2 || ap2 != 0 {
|
|
hp2 = math.Atan2(b2, ap2)
|
|
if hp2 < 0 {
|
|
hp2 += math.Pi * 2
|
|
}
|
|
hp2 *= 180 / math.Pi
|
|
}
|
|
|
|
deltaLp := l2 - l1
|
|
deltaCp := cp2 - cp1
|
|
dhp := 0.0
|
|
cpProduct := cp1 * cp2
|
|
if cpProduct != 0 {
|
|
dhp = hp2 - hp1
|
|
if dhp > 180 {
|
|
dhp -= 360
|
|
} else if dhp < -180 {
|
|
dhp += 360
|
|
}
|
|
}
|
|
deltaHp := 2 * math.Sqrt(cpProduct) * math.Sin(dhp/2*math.Pi/180)
|
|
|
|
lpmean := (l1 + l2) / 2
|
|
cpmean := (cp1 + cp2) / 2
|
|
hpmean := hp1 + hp2
|
|
if cpProduct != 0 {
|
|
hpmean /= 2
|
|
if math.Abs(hp1-hp2) > 180 {
|
|
if hp1+hp2 < 360 {
|
|
hpmean += 180
|
|
} else {
|
|
hpmean -= 180
|
|
}
|
|
}
|
|
}
|
|
|
|
t := 1 - 0.17*math.Cos((hpmean-30)*math.Pi/180) + 0.24*math.Cos(2*hpmean*math.Pi/180) + 0.32*math.Cos((3*hpmean+6)*math.Pi/180) - 0.2*math.Cos((4*hpmean-63)*math.Pi/180)
|
|
deltaTheta := 30 * math.Exp(-sq((hpmean-275)/25))
|
|
rc := 2 * math.Sqrt(math.Pow(cpmean, 7)/(math.Pow(cpmean, 7)+math.Pow(25, 7)))
|
|
sl := 1 + (0.015*sq(lpmean-50))/math.Sqrt(20+sq(lpmean-50))
|
|
sc := 1 + 0.045*cpmean
|
|
sh := 1 + 0.015*cpmean*t
|
|
rt := -math.Sin(2*deltaTheta*math.Pi/180) * rc
|
|
|
|
return math.Sqrt(sq(deltaLp/(kl*sl))+sq(deltaCp/(kc*sc))+sq(deltaHp/(kh*sh))+rt*(deltaCp/(kc*sc))*(deltaHp/(kh*sh))) * 0.01
|
|
}
|
|
|
|
// BlendLab blends two colors in the L*a*b* color-space, which should result in a smoother blend.
|
|
// t == 0 results in c1, t == 1 results in c2
|
|
func (c1 Color) BlendLab(c2 Color, t float64) Color {
|
|
l1, a1, b1 := c1.Lab()
|
|
l2, a2, b2 := c2.Lab()
|
|
return Lab(l1+t*(l2-l1),
|
|
a1+t*(a2-a1),
|
|
b1+t*(b2-b1))
|
|
}
|
|
|
|
/// L*u*v* ///
|
|
//////////////
|
|
// http://en.wikipedia.org/wiki/CIELUV#XYZ_.E2.86.92_CIELUV_and_CIELUV_.E2.86.92_XYZ_conversions
|
|
// For L*u*v*, we need to L*u*v*<->XYZ<->RGB and the first one is device dependent.
|
|
|
|
func XyzToLuv(x, y, z float64) (l, a, b float64) {
|
|
// Use D65 white as reference point by default.
|
|
// http://www.fredmiranda.com/forum/topic/1035332
|
|
// http://en.wikipedia.org/wiki/Standard_illuminant
|
|
return XyzToLuvWhiteRef(x, y, z, D65)
|
|
}
|
|
|
|
func XyzToLuvWhiteRef(x, y, z float64, wref [3]float64) (l, u, v float64) {
|
|
if y/wref[1] <= 6.0/29.0*6.0/29.0*6.0/29.0 {
|
|
l = y / wref[1] * 29.0 / 3.0 * 29.0 / 3.0 * 29.0 / 3.0
|
|
} else {
|
|
l = 1.16*math.Cbrt(y/wref[1]) - 0.16
|
|
}
|
|
ubis, vbis := xyz_to_uv(x, y, z)
|
|
un, vn := xyz_to_uv(wref[0], wref[1], wref[2])
|
|
u = 13.0 * l * (ubis - un)
|
|
v = 13.0 * l * (vbis - vn)
|
|
return
|
|
}
|
|
|
|
// For this part, we do as R's graphics.hcl does, not as wikipedia does.
|
|
// Or is it the same?
|
|
func xyz_to_uv(x, y, z float64) (u, v float64) {
|
|
denom := x + 15.0*y + 3.0*z
|
|
if denom == 0.0 {
|
|
u, v = 0.0, 0.0
|
|
} else {
|
|
u = 4.0 * x / denom
|
|
v = 9.0 * y / denom
|
|
}
|
|
return
|
|
}
|
|
|
|
func LuvToXyz(l, u, v float64) (x, y, z float64) {
|
|
// D65 white (see above).
|
|
return LuvToXyzWhiteRef(l, u, v, D65)
|
|
}
|
|
|
|
func LuvToXyzWhiteRef(l, u, v float64, wref [3]float64) (x, y, z float64) {
|
|
//y = wref[1] * lab_finv((l + 0.16) / 1.16)
|
|
if l <= 0.08 {
|
|
y = wref[1] * l * 100.0 * 3.0 / 29.0 * 3.0 / 29.0 * 3.0 / 29.0
|
|
} else {
|
|
y = wref[1] * cub((l+0.16)/1.16)
|
|
}
|
|
un, vn := xyz_to_uv(wref[0], wref[1], wref[2])
|
|
if l != 0.0 {
|
|
ubis := u/(13.0*l) + un
|
|
vbis := v/(13.0*l) + vn
|
|
x = y * 9.0 * ubis / (4.0 * vbis)
|
|
z = y * (12.0 - 3.0*ubis - 20.0*vbis) / (4.0 * vbis)
|
|
} else {
|
|
x, y = 0.0, 0.0
|
|
}
|
|
return
|
|
}
|
|
|
|
// Converts the given color to CIE L*u*v* space using D65 as reference white.
|
|
// L* is in [0..1] and both u* and v* are in about [-1..1]
|
|
func (col Color) Luv() (l, u, v float64) {
|
|
return XyzToLuv(col.Xyz())
|
|
}
|
|
|
|
// Converts the given color to CIE L*u*v* space, taking into account
|
|
// a given reference white. (i.e. the monitor's white)
|
|
// L* is in [0..1] and both u* and v* are in about [-1..1]
|
|
func (col Color) LuvWhiteRef(wref [3]float64) (l, u, v float64) {
|
|
x, y, z := col.Xyz()
|
|
return XyzToLuvWhiteRef(x, y, z, wref)
|
|
}
|
|
|
|
// Generates a color by using data given in CIE L*u*v* space using D65 as reference white.
|
|
// L* is in [0..1] and both u* and v* are in about [-1..1]
|
|
// WARNING: many combinations of `l`, `a`, and `b` values do not have corresponding
|
|
// valid RGB values, check the FAQ in the README if you're unsure.
|
|
func Luv(l, u, v float64) Color {
|
|
return Xyz(LuvToXyz(l, u, v))
|
|
}
|
|
|
|
// Generates a color by using data given in CIE L*u*v* space, taking
|
|
// into account a given reference white. (i.e. the monitor's white)
|
|
// L* is in [0..1] and both u* and v* are in about [-1..1]
|
|
func LuvWhiteRef(l, u, v float64, wref [3]float64) Color {
|
|
return Xyz(LuvToXyzWhiteRef(l, u, v, wref))
|
|
}
|
|
|
|
// DistanceLuv is a good measure of visual similarity between two colors!
|
|
// A result of 0 would mean identical colors, while a result of 1 or higher
|
|
// means the colors differ a lot.
|
|
func (c1 Color) DistanceLuv(c2 Color) float64 {
|
|
l1, u1, v1 := c1.Luv()
|
|
l2, u2, v2 := c2.Luv()
|
|
return math.Sqrt(sq(l1-l2) + sq(u1-u2) + sq(v1-v2))
|
|
}
|
|
|
|
// BlendLuv blends two colors in the CIE-L*u*v* color-space, which should result in a smoother blend.
|
|
// t == 0 results in c1, t == 1 results in c2
|
|
func (c1 Color) BlendLuv(c2 Color, t float64) Color {
|
|
l1, u1, v1 := c1.Luv()
|
|
l2, u2, v2 := c2.Luv()
|
|
return Luv(l1+t*(l2-l1),
|
|
u1+t*(u2-u1),
|
|
v1+t*(v2-v1))
|
|
}
|
|
|
|
/// HCL ///
|
|
///////////
|
|
// HCL is nothing else than L*a*b* in cylindrical coordinates!
|
|
// (this was wrong on English wikipedia, I fixed it, let's hope the fix stays.)
|
|
// But it is widely popular since it is a "correct HSV"
|
|
// http://www.hunterlab.com/appnotes/an09_96a.pdf
|
|
|
|
// Converts the given color to HCL space using D65 as reference white.
|
|
// H values are in [0..360], C and L values are in [0..1] although C can overshoot 1.0
|
|
func (col Color) Hcl() (h, c, l float64) {
|
|
return col.HclWhiteRef(D65)
|
|
}
|
|
|
|
func LabToHcl(L, a, b float64) (h, c, l float64) {
|
|
// Oops, floating point workaround necessary if a ~= b and both are very small (i.e. almost zero).
|
|
if math.Abs(b-a) > 1e-4 && math.Abs(a) > 1e-4 {
|
|
h = math.Mod(57.29577951308232087721*math.Atan2(b, a)+360.0, 360.0) // Rad2Deg
|
|
} else {
|
|
h = 0.0
|
|
}
|
|
c = math.Sqrt(sq(a) + sq(b))
|
|
l = L
|
|
return
|
|
}
|
|
|
|
// Converts the given color to HCL space, taking into account
|
|
// a given reference white. (i.e. the monitor's white)
|
|
// H values are in [0..360], C and L values are in [0..1]
|
|
func (col Color) HclWhiteRef(wref [3]float64) (h, c, l float64) {
|
|
L, a, b := col.LabWhiteRef(wref)
|
|
return LabToHcl(L, a, b)
|
|
}
|
|
|
|
// Generates a color by using data given in HCL space using D65 as reference white.
|
|
// H values are in [0..360], C and L values are in [0..1]
|
|
// WARNING: many combinations of `l`, `a`, and `b` values do not have corresponding
|
|
// valid RGB values, check the FAQ in the README if you're unsure.
|
|
func Hcl(h, c, l float64) Color {
|
|
return HclWhiteRef(h, c, l, D65)
|
|
}
|
|
|
|
func HclToLab(h, c, l float64) (L, a, b float64) {
|
|
H := 0.01745329251994329576 * h // Deg2Rad
|
|
a = c * math.Cos(H)
|
|
b = c * math.Sin(H)
|
|
L = l
|
|
return
|
|
}
|
|
|
|
// Generates a color by using data given in HCL space, taking
|
|
// into account a given reference white. (i.e. the monitor's white)
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// H values are in [0..360], C and L values are in [0..1]
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func HclWhiteRef(h, c, l float64, wref [3]float64) Color {
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L, a, b := HclToLab(h, c, l)
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return LabWhiteRef(L, a, b, wref)
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}
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// BlendHcl blends two colors in the CIE-L*C*h° color-space, which should result in a smoother blend.
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// t == 0 results in c1, t == 1 results in c2
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func (col1 Color) BlendHcl(col2 Color, t float64) Color {
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h1, c1, l1 := col1.Hcl()
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h2, c2, l2 := col2.Hcl()
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// We know that h are both in [0..360]
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return Hcl(interp_angle(h1, h2, t), c1+t*(c2-c1), l1+t*(l2-l1))
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}
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