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examples/blur: Fix comments about #694

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This commit is contained in:
Hajime Hoshi 2019-01-06 19:14:44 +09:00
parent b34834a895
commit aadfbc3e70
1 changed files with 6 additions and 2 deletions
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8
examples/blur/main.go
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@ -50,8 +50,12 @@ func update(screen *ebiten.Image) error {
for i := -3; i <= 3; i++ {
op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(i), 244+float64(j))
// Alpha scale should be 1.0/49.0, but accumulating 1/49 49 times doesn't reach to 1 due to
// errors (#694).
// Alpha scale should be 1.0/49.0, but accumulating 1/49 49 times doesn't reach to 1, because
// the final color is affected by the destination alpha when CompositeModeSourceOver is used.
// This composite mode is the default mode. See how this is calculated at the doc:
// https://godoc.org/github.com/hajimehoshi/ebiten#CompositeMode
//
// Use a higher value than 1.0/49.0. Here, 1.0/25.0 here to get a reasonable result.
op.ColorM.Scale(1, 1, 1, 1.0/25.0)
screen.DrawImage(gophersImage, op)
}