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Diffstat (limited to 'vendor/github.com/lucasb-eyer/go-colorful/colors.go')
| -rw-r--r-- | vendor/github.com/lucasb-eyer/go-colorful/colors.go | 797 |
1 files changed, 797 insertions, 0 deletions
diff --git a/vendor/github.com/lucasb-eyer/go-colorful/colors.go b/vendor/github.com/lucasb-eyer/go-colorful/colors.go new file mode 100644 index 0000000..f2fcf8c --- /dev/null +++ b/vendor/github.com/lucasb-eyer/go-colorful/colors.go @@ -0,0 +1,797 @@ +// The colorful package provides all kinds of functions for working with colors. +package colorful + +import( + "fmt" + "math" + "image/color" +) + +// A color is stored internally using sRGB (standard RGB) values in the range 0-1 +type Color struct { + R, G, B float64 +} + +// Implement the Go color.Color interface. +func (col Color) RGBA() (r, g, b, a uint32) { + r = uint32(col.R*65535.0+0.5) + g = uint32(col.G*65535.0+0.5) + b = uint32(col.B*65535.0+0.5) + a = 0xFFFF + return +} + +// Constructs a colorful.Color from something implementing color.Color +func MakeColor(col color.Color) Color { + r, g, b, a := col.RGBA() + + // Since color.Color is alpha pre-multiplied, we need to divide the + // RGB values by alpha again in order to get back the original RGB. + r *= 0xffff + r /= a + g *= 0xffff + g /= a + b *= 0xffff + b /= a + + return Color{float64(r)/65535.0, float64(g)/65535.0, float64(b)/65535.0} +} + +// Might come in handy sometimes to reduce boilerplate code. +func (col Color) RGB255() (r, g, b uint8) { + r = uint8(col.R*255.0+0.5) + g = uint8(col.G*255.0+0.5) + b = uint8(col.B*255.0+0.5) + return +} + +// This is the tolerance used when comparing colors using AlmostEqualRgb. +const Delta = 1.0/255.0 + +// This is the default reference white point. +var D65 = [3]float64{0.95047, 1.00000, 1.08883} + +// And another one. +var D50 = [3]float64{0.96422, 1.00000, 0.82521} + +// Checks whether the color exists in RGB space, i.e. all values are in [0..1] +func (c Color) IsValid() bool { + return 0.0 <= c.R && c.R <= 1.0 && + 0.0 <= c.G && c.G <= 1.0 && + 0.0 <= c.B && c.B <= 1.0 +} + +func clamp01(v float64) float64 { + return math.Max(0.0, math.Min(v, 1.0)) +} + +// Returns Clamps the color into valid range, clamping each value to [0..1] +// If the color is valid already, this is a no-op. +func (c Color) Clamped() Color { + return Color{clamp01(c.R), clamp01(c.G), clamp01(c.B)} +} + +func sq(v float64) float64 { + return v * v; +} + +func cub(v float64) float64 { + return v * v * v; +} + +// DistanceRgb computes the distance between two colors in RGB space. +// This is not a good measure! Rather do it in Lab space. +func (c1 Color) DistanceRgb(c2 Color) float64 { + return math.Sqrt(sq(c1.R-c2.R) + sq(c1.G-c2.G) + sq(c1.B-c2.B)) +} + +// Check for equality between colors within the tolerance Delta (1/255). +func (c1 Color) AlmostEqualRgb(c2 Color) bool { + return math.Abs(c1.R - c2.R) + + math.Abs(c1.G - c2.G) + + math.Abs(c1.B - c2.B) < 3.0*Delta +} + +// You don't really want to use this, do you? Go for BlendLab, BlendLuv or BlendHcl. +func (c1 Color) BlendRgb(c2 Color, t float64) Color { + return Color{c1.R + t*(c2.R - c1.R), + c1.G + t*(c2.G - c1.G), + c1.B + t*(c2.B - c1.B)} +} + +// Utility used by Hxx color-spaces for interpolating between two angles in [0,360]. +func interp_angle(a0, a1, t float64) float64 { + // Based on the answer here: http://stackoverflow.com/a/14498790/2366315 + // With potential proof that it works here: http://math.stackexchange.com/a/2144499 + delta := math.Mod(math.Mod(a1 - a0, 360.0) + 540, 360.0) - 180.0 + return math.Mod(a0 + t*delta + 360.0, 360.0) +} + + +/// HSV /// +/////////// +// From http://en.wikipedia.org/wiki/HSL_and_HSV +// Note that h is in [0..360] and s,v in [0..1] + +// Hsv returns the Hue [0..360], Saturation and Value [0..1] of the color. +func (col Color) Hsv() (h, s, v float64) { + min := math.Min(math.Min(col.R, col.G), col.B) + v = math.Max(math.Max(col.R, col.G), col.B) + C := v - min + + s = 0.0 + if v != 0.0 { + s = C / v + } + + h = 0.0 // We use 0 instead of undefined as in wp. + if min != v { + if v == col.R { h = math.Mod((col.G - col.B) / C, 6.0) } + if v == col.G { h = (col.B - col.R) / C + 2.0 } + if v == col.B { h = (col.R - col.G) / C + 4.0 } + h *= 60.0 + if h < 0.0 { h += 360.0 } + } + return +} + +// Hsv creates a new Color given a Hue in [0..360], a Saturation and a Value in [0..1] +func Hsv(H, S, V float64) Color { + Hp := H/60.0 + C := V*S + X := C*(1.0-math.Abs(math.Mod(Hp, 2.0)-1.0)) + + m := V-C; + r, g, b := 0.0, 0.0, 0.0 + + switch { + case 0.0 <= Hp && Hp < 1.0: r = C; g = X + case 1.0 <= Hp && Hp < 2.0: r = X; g = C + case 2.0 <= Hp && Hp < 3.0: g = C; b = X + case 3.0 <= Hp && Hp < 4.0: g = X; b = C + case 4.0 <= Hp && Hp < 5.0: r = X; b = C + case 5.0 <= Hp && Hp < 6.0: r = C; b = X + } + + return Color{m+r, m+g, m+b} +} + +// You don't really want to use this, do you? Go for BlendLab, BlendLuv or BlendHcl. +func (c1 Color) BlendHsv(c2 Color, t float64) Color { + h1, s1, v1 := c1.Hsv() + h2, s2, v2 := c2.Hsv() + + // We know that h are both in [0..360] + return Hsv(interp_angle(h1, h2, t), s1 + t*(s2 - s1), v1 + t*(v2 - v1)) +} + +/// HSL /// +/////////// + +// Hsl returns the Hue [0..360], Saturation [0..1], and Luminance (lightness) [0..1] of the color. +func (col Color) Hsl() (h, s, l float64) { + min := math.Min(math.Min(col.R, col.G), col.B) + max := math.Max(math.Max(col.R, col.G), col.B) + + l = (max + min) / 2 + + if min == max { + s = 0 + h = 0 + } else { + if l < 0.5 { + s = (max - min) / (max + min) + } else { + s = (max - min) / (2.0 - max - min) + } + + if max == col.R { + h = (col.G - col.B) / (max - min) + } else if max == col.G { + h = 2.0 + (col.B-col.R)/(max-min) + } else { + h = 4.0 + (col.R-col.G)/(max-min) + } + + h *= 60 + + if h < 0 { + h += 360 + } + } + + return +} + +// Hsl creates a new Color given a Hue in [0..360], a Saturation [0..1], and a Luminance (lightness) in [0..1] +func Hsl(h, s, l float64) Color { + if s == 0 { + return Color{l, l, l} + } + + var r, g, b float64 + var t1 float64 + var t2 float64 + var tr float64 + var tg float64 + var tb float64 + + if l < 0.5 { + t1 = l * (1.0 + s) + } else { + t1 = l + s - l*s + } + + t2 = 2*l - t1 + h = h / 360 + tr = h + 1.0/3.0 + tg = h + tb = h - 1.0/3.0 + + if tr < 0 { + tr += 1 + } + if tr > 1 { + tr -= 1 + } + if tg < 0 { + tg += 1 + } + if tg > 1 { + tg -= 1 + } + if tb < 0 { + tb += 1 + } + if tb > 1 { + tb -= 1 + } + + // Red + if 6*tr < 1 { + r = t2 + (t1-t2)*6*tr + } else if 2*tr < 1 { + r = t1 + } else if 3*tr < 2 { + r = t2 + (t1-t2)*(2.0/3.0-tr)*6 + } else { + r = t2 + } + + // Green + if 6*tg < 1 { + g = t2 + (t1-t2)*6*tg + } else if 2*tg < 1 { + g = t1 + } else if 3*tg < 2 { + g = t2 + (t1-t2)*(2.0/3.0-tg)*6 + } else { + g = t2 + } + + // Blue + if 6*tb < 1 { + b = t2 + (t1-t2)*6*tb + } else if 2*tb < 1 { + b = t1 + } else if 3*tb < 2 { + b = t2 + (t1-t2)*(2.0/3.0-tb)*6 + } else { + b = t2 + } + + return Color{r, g, b} +} + +/// Hex /// +/////////// + +// Hex returns the hex "html" representation of the color, as in #ff0080. +func (col Color) Hex() string { + // Add 0.5 for rounding + 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)) +} + +// Hex parses a "html" hex color-string, either in the 3 "#f0c" or 6 "#ff1034" digits form. +func Hex(scol string) (Color, error) { + format := "#%02x%02x%02x" + factor := 1.0/255.0 + if len(scol) == 4 { + format = "#%1x%1x%1x" + factor = 1.0/15.0 + } + + var r, g, b uint8 + n, err := fmt.Sscanf(scol, format, &r, &g, &b) + if err != nil { + return Color{}, err + } + if n != 3 { + return Color{}, fmt.Errorf("color: %v is not a hex-color", scol) + } + + return Color{float64(r)*factor, float64(g)*factor, float64(b)*factor}, nil +} + +/// Linear /// +////////////// +// http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/ +// http://www.brucelindbloom.com/Eqn_RGB_to_XYZ.html + +func linearize(v float64) float64 { + if v <= 0.04045 { + return v / 12.92 + } + return math.Pow((v + 0.055)/1.055, 2.4) +} + +// LinearRgb converts the color into the linear RGB space (see http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/). +func (col Color) LinearRgb() (r, g, b float64) { + r = linearize(col.R) + g = linearize(col.G) + b = linearize(col.B) + return +} + +// A much faster and still quite precise linearization using a 6th-order Taylor approximation. +// See the accompanying Jupyter notebook for derivation of the constants. +func linearize_fast(v float64) float64 { + v1 := v - 0.5 + v2 := v1*v1 + v3 := v2*v1 + v4 := v2*v2 + //v5 := v3*v2 + return -0.248750514614486 + 0.925583310193438*v + 1.16740237321695*v2 + 0.280457026598666*v3 - 0.0757991963780179*v4 //+ 0.0437040411548932*v5 +} + +// FastLinearRgb is much faster than and almost as accurate as LinearRgb. +// BUT it is important to NOTE that they only produce good results for valid colors r,g,b in [0,1]. +func (col Color) FastLinearRgb() (r, g, b float64) { + r = linearize_fast(col.R) + g = linearize_fast(col.G) + b = linearize_fast(col.B) + return +} + +func delinearize(v float64) float64 { + if v <= 0.0031308 { + return 12.92 * v + } + return 1.055 * math.Pow(v, 1.0/2.4) - 0.055 +} + +// LinearRgb creates an sRGB color out of the given linear RGB color (see http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/). +func LinearRgb(r, g, b float64) Color { + return Color{delinearize(r), delinearize(g), delinearize(b)} +} + +func delinearize_fast(v float64) float64 { + // This function (fractional root) is much harder to linearize, so we need to split. + if v > 0.2 { + v1 := v - 0.6 + v2 := v1*v1 + v3 := v2*v1 + v4 := v2*v2 + v5 := v3*v2 + return 0.442430344268235 + 0.592178981271708*v - 0.287864782562636*v2 + 0.253214392068985*v3 - 0.272557158129811*v4 + 0.325554383321718*v5 + } else if v > 0.03 { + v1 := v - 0.115 + v2 := v1*v1 + v3 := v2*v1 + v4 := v2*v2 + v5 := v3*v2 + return 0.194915592891669 + 1.55227076330229*v - 3.93691860257828*v2 + 18.0679839248761*v3 - 101.468750302746*v4 + 632.341487393927*v5 + } else { + v1 := v - 0.015 + v2 := v1*v1 + v3 := v2*v1 + v4 := v2*v2 + v5 := v3*v2 + // You can clearly see from the involved constants that the low-end is highly nonlinear. + return 0.0519565234928877 + 5.09316778537561*v - 99.0338180489702*v2 + 3484.52322764895*v3 - 150028.083412663*v4 + 7168008.42971613*v5 + } +} + +// FastLinearRgb is much faster than and almost as accurate as LinearRgb. +// BUT it is important to NOTE that they only produce good results for valid inputs r,g,b in [0,1]. +func FastLinearRgb(r, g, b float64) Color { + return Color{delinearize_fast(r), delinearize_fast(g), delinearize_fast(b)} +} + +// XyzToLinearRgb converts from CIE XYZ-space to Linear RGB space. +func XyzToLinearRgb(x, y, z float64) (r, g, b float64) { + r = 3.2404542*x - 1.5371385*y - 0.4985314*z + g = -0.9692660*x + 1.8760108*y + 0.0415560*z + b = 0.0556434*x - 0.2040259*y + 1.0572252*z + return +} + +func LinearRgbToXyz(r, g, b float64) (x, y, z float64) { + x = 0.4124564*r + 0.3575761*g + 0.1804375*b + y = 0.2126729*r + 0.7151522*g + 0.0721750*b + z = 0.0193339*r + 0.1191920*g + 0.9503041*b + return +} + +/// XYZ /// +/////////// +// http://www.sjbrown.co.uk/2004/05/14/gamma-correct-rendering/ + +func (col Color) Xyz() (x, y, z float64) { + return LinearRgbToXyz(col.LinearRgb()) +} + +func Xyz(x, y, z float64) Color { + return LinearRgb(XyzToLinearRgb(x, y, z)) +} + +/// xyY /// +/////////// +// http://www.brucelindbloom.com/Eqn_XYZ_to_xyY.html + +// Well, the name is bad, since it's xyY but Golang needs me to start with a +// capital letter to make the method public. +func XyzToXyy(X, Y, Z float64) (x, y, Yout float64) { + return XyzToXyyWhiteRef(X, Y, Z, D65) +} + +func XyzToXyyWhiteRef(X, Y, Z float64, wref [3]float64) (x, y, Yout float64) { + Yout = Y + N := X + Y + Z + if math.Abs(N) < 1e-14 { + // When we have black, Bruce Lindbloom recommends to use + // the reference white's chromacity for x and y. + x = wref[0] / (wref[0] + wref[1] + wref[2]) + y = wref[1] / (wref[0] + wref[1] + wref[2]) + } else { + x = X / N + y = Y / N + } + return +} + +func XyyToXyz(x, y, Y float64) (X, Yout, Z float64) { + Yout = Y + + 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. +} + +// 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) +// H values are in [0..360], C and L values are in [0..1] +func HclWhiteRef(h, c, l float64, wref [3]float64) Color { + L, a, b := HclToLab(h, c, l) + return LabWhiteRef(L, a, b, wref) +} + +// BlendHcl blends two colors in the CIE-L*C*h° color-space, which should result in a smoother blend. +// t == 0 results in c1, t == 1 results in c2 +func (col1 Color) BlendHcl(col2 Color, t float64) Color { + h1, c1, l1 := col1.Hcl() + h2, c2, l2 := col2.Hcl() + + // We know that h are both in [0..360] + return Hcl(interp_angle(h1, h2, t), c1 + t*(c2 - c1), l1 + t*(l2 - l1)) +} |