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colorm: add DrawImageOptions.ColorScale

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Closes #3188
This commit is contained in:
Hajime Hoshi 2025-02-01 13:52:23 +09:00
parent 0dabcbc65b
commit 26eafc6f3a
2 changed files with 25 additions and 0 deletions
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10
colorm/draw.go
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@ -25,6 +25,15 @@ type DrawImageOptions struct {
// The default (zero) value is identity, which draws the image at (0, 0).
GeoM ebiten.GeoM
// ColorScale is a scale of color.
//
// ColorScale is slightly different from colorm.ColorM's Scale in terms of alphas.
// ColorScale is applied to premultiplied-alpha colors, while colorm.ColorM is applied to straight-alpha colors.
// Thus, ColorM.Scale(r, g, b, a) equals to ColorScale.Scale(r*a, g*a, b*a, a).
//
// The default (zero) value is identity, which is (1, 1, 1, 1).
ColorScale ebiten.ColorScale
// Blend is a blending way of the source color and the destination color.
// The default (zero) value is the regular alpha blending.
Blend ebiten.Blend
@ -44,6 +53,7 @@ func DrawImage(dst, src *ebiten.Image, colorM ColorM, op *DrawImageOptions) {
opShader := &ebiten.DrawRectShaderOptions{}
opShader.GeoM = op.GeoM
opShader.ColorScale = op.ColorScale
opShader.CompositeMode = ebiten.CompositeModeCustom
opShader.Blend = op.Blend
opShader.Uniforms = uniforms(colorM)

15
colorm/draw_test.go
View File

@ -299,3 +299,18 @@ func TestColorMCopy(t *testing.T) {
}
}
}
func TestColorScale(t *testing.T) {
dst := ebiten.NewImage(1, 1)
src := ebiten.NewImage(1, 1)
src.Fill(color.White)
op := &colorm.DrawImageOptions{}
op.ColorScale.Scale(0.25, 0.5, 0.5, 0.5)
var cm colorm.ColorM
cm.Scale(1, 0.5, 1, 0.5)
colorm.DrawImage(dst, src, cm, op)
if got, want := dst.At(0, 0).(color.RGBA), (color.RGBA{0x20, 0x20, 0x40, 0x40}); !sameColors(got, want, 1) {
t.Errorf("got: %v, want: %v", got, want)
}
}