ebiten/docs/examples/masking.html
2017-08-18 23:43:08 +09:00

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<h2>Ebiten example - masking</h2>
<iframe src="masking.content.html" width="640" height="480"></iframe>
<div class="card"><pre class="card-body"><code class="language-go">// &#43;build example
package main
import (
&#34;image&#34;
&#34;image/color&#34;
_ &#34;image/jpeg&#34;
&#34;log&#34;
&#34;math&#34;
&#34;github.com/hajimehoshi/ebiten&#34;
&#34;github.com/hajimehoshi/ebiten/ebitenutil&#34;
)
const (
screenWidth = 320
screenHeight = 240
)
var (
gophersImage *ebiten.Image
fiveyearsImage *ebiten.Image
maskImage *ebiten.Image
spotLightImage *ebiten.Image
spotLightX = 0
spotLightY = 0
spotLightVX = 1
spotLightVY = 1
)
func update(screen *ebiten.Image) error {
spotLightX &#43;= spotLightVX
spotLightY &#43;= spotLightVY
if spotLightX &lt; 0 {
spotLightX = -spotLightX
spotLightVX = -spotLightVX
}
if spotLightY &lt; 0 {
spotLightY = -spotLightY
spotLightVY = -spotLightVY
}
w, h := spotLightImage.Size()
maxX, maxY := screenWidth-w, screenHeight-h
if maxX &lt; spotLightX {
spotLightX = -spotLightX &#43; 2*maxX
spotLightVX = -spotLightVX
}
if maxY &lt; spotLightY {
spotLightY = -spotLightY &#43; 2*maxY
spotLightVY = -spotLightVY
}
if ebiten.IsRunningSlowly() {
return nil
}
maskImage.Clear()
op := &amp;ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(spotLightX), float64(spotLightY))
maskImage.DrawImage(spotLightImage, op)
op = &amp;ebiten.DrawImageOptions{}
op.CompositeMode = ebiten.CompositeModeSourceOut
maskImage.DrawImage(fiveyearsImage, op)
screen.Fill(color.RGBA{0x00, 0x00, 0x80, 0xff})
screen.DrawImage(gophersImage, &amp;ebiten.DrawImageOptions{})
screen.DrawImage(maskImage, &amp;ebiten.DrawImageOptions{})
return nil
}
func max(a, b int) int {
if a &lt; b {
return b
}
return a
}
func min(a, b int) int {
if a &lt; b {
return a
}
return b
}
func main() {
var err error
gophersImage, _, err = ebitenutil.NewImageFromFile(&#34;_resources/images/gophers.jpg&#34;, ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
fiveyearsImage, _, err = ebitenutil.NewImageFromFile(&#34;_resources/images/fiveyears.jpg&#34;, ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
maskImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
as := image.Point{128, 128}
a := image.NewAlpha(image.Rectangle{image.ZP, as})
for j := 0; j &lt; as.Y; j&#43;&#43; {
for i := 0; i &lt; as.X; i&#43;&#43; {
r := as.X / 2
d := math.Sqrt(float64((i-r)*(i-r) &#43; (j-r)*(j-r)))
b := uint8(max(0, min(0xff, 3*0xff-int(d*3*0xff)/r)))
a.SetAlpha(i, j, color.Alpha{b})
}
}
spotLightImage, _ = ebiten.NewImageFromImage(a, ebiten.FilterNearest)
if err := ebiten.Run(update, screenWidth, screenHeight, 2, &#34;Masking (Ebiten Demo)&#34;); err != nil {
log.Fatal(err)
}
}
</code></pre></div>
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