ebiten/internal/affine/colorm.go

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// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package affine
import (
"math"
)
// ColorMDim is a dimension of a ColorM.
const ColorMDim = 5
// A ColorM represents a matrix to transform coloring when rendering an image.
//
// A ColorM is applied to the source alpha color
// while an Image's pixels' format is alpha premultiplied.
// Before applying a matrix, a color is un-multiplied, and after applying the matrix,
// the color is multiplied again.
//
// The initial value is identity.
type ColorM struct {
initialized bool
es [(ColorMDim - 1) * (ColorMDim)]float64
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}
func (c *ColorM) dim() int {
return ColorMDim
}
func (c *ColorM) initialize() {
c.initialized = true
for i := 0; i < ColorMDim-1; i++ {
c.es[i*ColorMDim+i] = 1
}
}
// Element returns a value of a matrix at (i, j).
func (c *ColorM) Element(i, j int) float64 {
if !c.initialized {
if i == j {
return 1
}
return 0
}
return c.es[i*ColorMDim+j]
}
// SetElement sets an element at (i, j).
func (c *ColorM) SetElement(i, j int, element float64) {
if !c.initialized {
c.initialize()
}
c.es[i*ColorMDim+j] = element
}
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func (c *ColorM) Equals(other *ColorM) bool {
if !c.initialized {
c.initialize()
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}
if !other.initialized {
other.initialize()
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}
return c.es == other.es
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}
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// Concat multiplies a color matrix with the other color matrix.
// This is same as muptiplying the matrix other and the matrix c in this order.
func (c *ColorM) Concat(other ColorM) {
result := ColorM{}
mul(&other, c, &result)
*c = result
}
// Add adds a color matrix with the other color matrix.
func (c *ColorM) Add(other ColorM) {
result := ColorM{}
add(&other, c, &result)
*c = result
}
// Scale scales the matrix by (r, g, b, a).
func (c *ColorM) Scale(r, g, b, a float64) {
for i := 0; i < ColorMDim; i++ {
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c.SetElement(0, i, c.Element(0, i)*r)
c.SetElement(1, i, c.Element(1, i)*g)
c.SetElement(2, i, c.Element(2, i)*b)
c.SetElement(3, i, c.Element(3, i)*a)
}
}
// Translate translates the matrix by (r, g, b, a).
func (c *ColorM) Translate(r, g, b, a float64) {
c.SetElement(0, 4, c.Element(0, 4)+r)
c.SetElement(1, 4, c.Element(1, 4)+g)
c.SetElement(2, 4, c.Element(2, 4)+b)
c.SetElement(3, 4, c.Element(3, 4)+a)
}
// RotateHue rotates the hue.
func (c *ColorM) RotateHue(theta float64) {
c.ChangeHSV(theta, 1, 1)
}
var (
// The YCbCr value ranges are:
// Y: [ 0 - 1 ]
// Cb: [-0.5 - 0.5]
// Cr: [-0.5 - 0.5]
rgbToYCbCr = ColorM{
initialized: true,
es: [...]float64{
0.2990, 0.5870, 0.1140, 0, 0,
-0.1687, -0.3313, 0.5000, 0, 0,
0.5000, -0.4187, -0.0813, 0, 0,
0, 0, 0, 1, 0,
},
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}
yCbCrToRgb = ColorM{
initialized: true,
es: [...]float64{
1, 0, 1.40200, 0, 0,
1, -0.34414, -0.71414, 0, 0,
1, 1.77200, 0, 0, 0,
0, 0, 0, 1, 0,
},
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}
)
// ChangeHSV changes HSV (Hue-Saturation-Value) values.
// hueTheta is a radian value to ratate hue.
// saturationScale is a value to scale saturation.
// valueScale is a value to scale value (a.k.a. brightness).
//
// This conversion uses RGB to/from YCrCb conversion.
func (c *ColorM) ChangeHSV(hueTheta float64, saturationScale float64, valueScale float64) {
sin, cos := math.Sincos(hueTheta)
c.Concat(rgbToYCbCr)
c.Concat(ColorM{
initialized: true,
es: [...]float64{
1, 0, 0, 0, 0,
0, cos, -sin, 0, 0,
0, sin, cos, 0, 0,
0, 0, 0, 1, 0,
},
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})
s := saturationScale
v := valueScale
c.Scale(v, s*v, s*v, 1)
c.Concat(yCbCrToRgb)
}
var monochrome ColorM
func init() {
monochrome.ChangeHSV(0, 0, 1)
}
// Monochrome returns a color matrix to make an image monochrome.
func Monochrome() ColorM {
return monochrome
}
// ScaleColor is deprecated as of 1.2.0-alpha. Use Scale instead.
func ScaleColor(r, g, b, a float64) ColorM {
return ColorM{
initialized: true,
es: [...]float64{
r, 0, 0, 0, 0,
0, g, 0, 0, 0,
0, 0, b, 0, 0,
0, 0, 0, a, 0,
},
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}
}
// TranslateColor is deprecated as of 1.2.0-alpha. Use Translate instead.
func TranslateColor(r, g, b, a float64) ColorM {
return ColorM{
initialized: true,
es: [...]float64{
1, 0, 0, 0, r,
0, 1, 0, 0, g,
0, 0, 1, 0, b,
0, 0, 0, 1, a,
},
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}
}
// RotateHue is deprecated as of 1.2.0-alpha. Use RotateHue member function instead.
func RotateHue(theta float64) ColorM {
c := ColorM{}
c.RotateHue(theta)
return c
}