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<!DOCTYPE html>
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< script src = "../scripts/force-https.js" > < / script >
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< link rel = "shortcut icon" href = "../favicon.png" type = "image/png" >
< link rel = "icon" href = "../favicon.png" type = "image/png" >
< title > Ebiten example - masking< / title >
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< link rel = "stylesheet" href = "../stylesheets/bootstrap.min.css" >
< link rel = "stylesheet" href = "../stylesheets/highlight-github.css" >
< link rel = "stylesheet" href = "../stylesheets/ebiten.css" >
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< script src = "../scripts/googleanalytics.js" > < / script >
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< header class = "navbar" > < div class = "container" >
< div class = "navbar-header" >
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< a class = "navbar-brand" href = ".." > Ebiten< / a >
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< / div >
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< nav class = "collapse navbar-collapse" >
< ul class = "nav navbar-nav navbar-right" >
< li > < a href = "https://github.com/hajimehoshi/ebiten" > GitHub< / a > < / li >
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< li > < a href = "https://godoc.org/github.com/hajimehoshi/ebiten" > GoDoc< / a > < / li >
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< li > < a href = "https://github.com/hajimehoshi/ebiten/wiki" > Wiki< / a >
< / ul >
< / nav >
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< / header >
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< main > < div class = "container" >
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< h2 > Ebiten example - masking< / h2 >
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< iframe src = "masking.content.html" width = "640" height = "480" > < / iframe >
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< pre > < code class = "language-go" > // + build example
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package main
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import (
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" image"
" image/color"
_ " image/jpeg"
" log"
" math"
" github.com/hajimehoshi/ebiten"
" github.com/hajimehoshi/ebiten/ebitenutil"
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)
const (
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screenWidth = 320
screenHeight = 240
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)
var (
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gophersImage *ebiten.Image
fiveyearsImage *ebiten.Image
maskImage *ebiten.Image
spotLightImage *ebiten.Image
spotLightX = 0
spotLightY = 0
spotLightVX = 1
spotLightVY = 1
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)
func update(screen *ebiten.Image) error {
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spotLightX + = spotLightVX
spotLightY + = spotLightVY
if spotLightX < 0 {
spotLightX = -spotLightX
spotLightVX = -spotLightVX
}
if spotLightY < 0 {
spotLightY = -spotLightY
spotLightVY = -spotLightVY
}
w, h := spotLightImage.Size()
maxX, maxY := screenWidth-w, screenHeight-h
if maxX < spotLightX {
spotLightX = -spotLightX + 2*maxX
spotLightVX = -spotLightVX
}
if maxY < spotLightY {
spotLightY = -spotLightY + 2*maxY
spotLightVY = -spotLightVY
}
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if ebiten.IsRunningSlowly() {
return nil
}
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maskImage.Clear()
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op := & ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(spotLightX), float64(spotLightY))
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maskImage.DrawImage(spotLightImage, op)
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op = & ebiten.DrawImageOptions{}
op.CompositeMode = ebiten.CompositeModeSourceOut
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maskImage.DrawImage(fiveyearsImage, op)
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screen.Fill(color.RGBA{0x00, 0x00, 0x80, 0xff})
screen.DrawImage(gophersImage, & ebiten.DrawImageOptions{})
screen.DrawImage(maskImage, & ebiten.DrawImageOptions{})
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return nil
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}
func max(a, b int) int {
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if a < b {
return b
}
return a
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}
func min(a, b int) int {
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if a < b {
return a
}
return b
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}
func main() {
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var err error
gophersImage, _, err = ebitenutil.NewImageFromFile(" _resources/images/gophers.jpg" , ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
fiveyearsImage, _, err = ebitenutil.NewImageFromFile(" _resources/images/fiveyears.jpg" , ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
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maskImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
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as := image.Point{128, 128}
a := image.NewAlpha(image.Rectangle{image.ZP, as})
for j := 0; j < as.Y; j+ + {
for i := 0; i < as.X; i+ + {
r := as.X / 2
d := math.Sqrt(float64((i-r)*(i-r) + (j-r)*(j-r)))
b := uint8(max(0, min(0xff, 3*0xff-int(d*3*0xff)/r)))
a.SetAlpha(i, j, color.Alpha{b})
}
}
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spotLightImage, _ = ebiten.NewImageFromImage(a, ebiten.FilterNearest)
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, " Masking (Ebiten Demo)" ); err != nil {
log.Fatal(err)
}
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}
< / code > < / pre >
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< / div > < / main >
< footer > < div class = "container" >
< p > © 2013 Hajime Hoshi< / p >
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< p > Code is licensed under < a href = "https://github.com/hajimehoshi/ebiten/blob/master/LICENSE" > the Apache License 2.0< / a > .< / p >
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< p > The content of this page is licensed under < a href = "https://creativecommons.org/licenses/by/4.0/" > the Creative Commons Attribution 4.0 License< / a > .< / p >
< / div > < / footer >
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< script src = "../scripts/highlight.pack.js" > < / script >
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< script > hljs . initHighlightingOnLoad ( ) ; < / script >
