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< h2 > Ebiten example - mandelbrot< / h2 >
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< div class = "card" > < pre class = "card-body" > < code class = "language-go" > // + build example jsgo
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package main
import (
" log"
" math"
" github.com/hajimehoshi/ebiten"
)
const (
screenWidth = 640
screenHeight = 640
maxIt = 128
)
var (
offscreen *ebiten.Image
offscreenPix []byte
palette [maxIt]byte
)
func init() {
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offscreen, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
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offscreenPix = make([]byte, screenWidth*screenHeight*4)
for i := range palette {
palette[i] = byte(math.Sqrt(float64(i)/float64(len(palette))) * 0x80)
}
}
func color(it int) (r, g, b byte) {
if it == maxIt {
return 0xff, 0xff, 0xff
}
c := palette[it]
return c, c, c
}
func updateOffscreen(centerX, centerY, size float64) {
for j := 0; j < screenHeight; j+ + {
for i := 0; i < screenHeight; i+ + {
x := float64(i)*size/screenWidth - size/2 + centerX
y := (screenHeight-float64(j))*size/screenHeight - size/2 + centerY
c := complex(x, y)
z := complex(0, 0)
it := 0
for ; it < maxIt; it+ + {
z = z*z + c
if real(z)*real(z)+ imag(z)*imag(z) > 4 {
break
}
}
r, g, b := color(it)
p := 4 * (i + j*screenWidth)
offscreenPix[p] = r
offscreenPix[p+ 1] = g
offscreenPix[p+ 2] = b
offscreenPix[p+ 3] = 0xff
}
}
offscreen.ReplacePixels(offscreenPix)
}
func init() {
// Now it is not feasible to call updateOffscreen every frame due to performance.
updateOffscreen(-0.75, 0.25, 2)
}
func update(screen *ebiten.Image) error {
if ebiten.IsRunningSlowly() {
return nil
}
screen.DrawImage(offscreen, nil)
return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 1, " Mandelbrot (Ebiten Demo)" ); err != nil {
log.Fatal(err)
}
}
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