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Revert the algorithm of RotateHue

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This commit is contained in:
Hajime Hoshi 2014-12-15 10:55:40 +09:00
parent 3cf449c52c
commit 46a9901be8
1 changed files with 7 additions and 24 deletions
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31
colormatrix.go
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@ -110,34 +110,17 @@ func TranslateColor(clr color.Color) ColorMatrix {
// RotateHue returns a color matrix to rotate the hue
func RotateHue(theta float64) ColorMatrix {
sin, cos := math.Sincos(theta)
// RBG to YIQ
c := ColorMatrix{
v1 := cos + (1.0 - cos) / 3.0
v2 := (1.0 / 3.0) * (1.0 - cos) - math.Sqrt(1.0 / 3.0) * sin
v3 := (1.0 / 3.0) * (1.0 - cos) + math.Sqrt(1.0 / 3.0) * sin
return ColorMatrix{
[ColorMatrixDim - 1][ColorMatrixDim]float64{
{0.299, 0.587, 0.114, 0, 0},
{0.596, -0.275, -0.321, 0, 0},
{0.212, -0.523, 0.311, 0, 0},
{v1, v2, v3, 0, 0},
{v3, v1, v2, 0, 0},
{v2, v3, v1, 0, 0},
{0, 0, 0, 1, 0},
},
}
// Rotate around the Y axis
c.Concat(ColorMatrix{
[ColorMatrixDim - 1][ColorMatrixDim]float64{
{1, 0, 0, 0, 0},
{0, cos, sin, 0, 0},
{0, -sin, cos, 0, 0},
{0, 0, 0, 1, 0},
},
})
// YIQ to RGB
c.Concat(ColorMatrix{
[ColorMatrixDim - 1][ColorMatrixDim]float64{
{1, 0.956, 0.621, 0, 0},
{1, -0.272, -0.647, 0, 0},
{1, -1.105, 1.702, 0, 0},
{0, 0, 0, 1, 0},
},
})
return c
}
func rgba(clr color.Color) (float64, float64, float64, float64) {