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<!DOCTYPE html>
< 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/ebiten.css" >
< header class = "navbar" > < div class = "container" >
< div class = "navbar-header" >
< a class = "navbar-brand" href = "/" > Ebiten< / a >
< / div >
< / header >
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< main > < div class = "container" >
< h1 > Ebiten example - masking< / h1 >
< iframe src = "masking.content.html" width = "640" height = "480" > < / iframe >
< pre > < code > // + build example
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package main
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import (
" image"
" image/color"
_ " image/jpeg"
" log"
" math"
" github.com/hajimehoshi/ebiten"
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" github.com/hajimehoshi/ebiten/ebitenutil"
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)
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 + = 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
}
if err := maskImage.Clear(); err != nil {
return err
}
op := & ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(spotLightX), float64(spotLightY))
if err := maskImage.DrawImage(spotLightImage, op); err != nil {
return err
}
op = & ebiten.DrawImageOptions{}
op.CompositeMode = ebiten.CompositeModeSourceOut
if err := maskImage.DrawImage(fiveyearsImage, op); err != nil {
return err
}
if err := screen.Fill(color.RGBA{0x00, 0x00, 0x80, 0xff}); err != nil {
return err
}
if err := screen.DrawImage(gophersImage, & ebiten.DrawImageOptions{}); err != nil {
return err
}
if err := screen.DrawImage(maskImage, & ebiten.DrawImageOptions{}); err != nil {
return err
}
return nil
}
func max(a, b int) int {
if a < b {
return b
}
return a
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
func main() {
var err error
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gophersImage, _, err = ebitenutil.NewImageFromFile(" _resources/images/gophers.jpg" , ebiten.FilterNearest)
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if err != nil {
log.Fatal(err)
}
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fiveyearsImage, _, err = ebitenutil.NewImageFromFile(" _resources/images/fiveyears.jpg" , ebiten.FilterNearest)
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if err != nil {
log.Fatal(err)
}
maskImage, err = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
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})
}
}
spotLightImage, err = ebiten.NewImageFromImage(a, ebiten.FilterNearest)
if err != nil {
log.Fatal(err)
}
if err := ebiten.Run(update, screenWidth, screenHeight, 2, " Masking (Ebiten Demo)" ); err != nil {
log.Fatal(err)
}
}
< / code > < / pre >
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< / div > < / main >
< footer > < div class = "container" >
< p > © 2013 Hajime Hoshi< / p >
< p > Code is licensed under < a href = "https://github.com/hajimehoshi/ebiten/blob/master/LICENSE" > Apache License 2.0< / a > .< / p >
< 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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