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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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package ebiten
import (
// ColorMDim is a dimension of a ColorM.
const ColorMDim = affine.ColorMDim
// A ColorM represents a matrix to transform coloring when rendering an image.
// A ColorM is applied to the straight 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 {
impl *affine.ColorM
// String returns a string representation of ColorM.
func (c *ColorM) String() string {
b, t := c.impl.UnsafeElements()
return fmt.Sprintf("[[%f, %f, %f, %f, %f], [%f, %f, %f, %f, %f], [%f, %f, %f, %f, %f], [%f, %f, %f, %f, %f]]",
b[0], b[4], b[8], b[12], t[0],
b[1], b[5], b[9], b[13], t[1],
b[2], b[6], b[10], b[14], t[2],
b[3], b[7], b[11], b[15], t[3])
// Reset resets the ColorM as identity.
func (c *ColorM) Reset() {
c.impl = nil
// Apply pre-multiplies a vector (r, g, b, a, 1) by the matrix
// where r, g, b, and a are clr's values in straight-alpha format.
// In other words, Apply calculates ColorM * (r, g, b, a, 1)^T.
func (c *ColorM) Apply(clr color.Color) color.Color {
return c.impl.Apply(clr)
// 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) {
c.impl = c.impl.Concat(other.impl)
// Add is deprecated as of 1.5.0-alpha.
// Note that this doesn't make sense as an operation for affine matrices.
func (c *ColorM) Add(other ColorM) {
c.impl = c.impl.Add(other.impl)
// Scale scales the matrix by (r, g, b, a).
func (c *ColorM) Scale(r, g, b, a float64) {
c.impl = c.impl.Scale(float32(r), float32(g), float32(b), float32(a))
// Translate translates the matrix by (r, g, b, a).
func (c *ColorM) Translate(r, g, b, a float64) {
c.impl = c.impl.Translate(float32(r), float32(g), float32(b), float32(a))
// RotateHue rotates the hue.
// theta represents rotating angle in radian.
func (c *ColorM) RotateHue(theta float64) {
c.ChangeHSV(theta, 1, 1)
// ChangeHSV changes HSV (Hue-Saturation-Value) values.
// hueTheta is a radian value to rotate 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) {
c.impl = c.impl.ChangeHSV(hueTheta, float32(saturationScale), float32(valueScale))
// Element returns a value of a matrix at (i, j).
func (c *ColorM) Element(i, j int) float64 {
b, t := c.impl.UnsafeElements()
if j < ColorMDim-1 {
return float64(b[i+j*(ColorMDim-1)])
return float64(t[i])
// SetElement sets an element at (i, j).
func (c *ColorM) SetElement(i, j int, element float64) {
c.impl = c.impl.SetElement(i, j, float32(element))
// Monochrome is deprecated as of 1.6.0-alpha. Use ChangeHSV(0, 0, 1) instead.
func Monochrome() ColorM {
c := ColorM{}
c.ChangeHSV(0, 0, 1)
return c
// ScaleColor is deprecated as of 1.2.0-alpha. Use Scale instead.
func ScaleColor(r, g, b, a float64) ColorM {
c := ColorM{}
c.Scale(r, g, b, a)
return c
// TranslateColor is deprecated as of 1.2.0-alpha. Use Translate instead.
func TranslateColor(r, g, b, a float64) ColorM {
c := ColorM{}
c.Translate(r, g, b, a)
return c
// RotateHue is deprecated as of 1.2.0-alpha. Use RotateHue member function instead.
func RotateHue(theta float64) ColorM {
c := ColorM{}
return c
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