ebiten/docs/examples/mandelbrot.html
2018-03-21 14:34:48 +09:00

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<h2>Ebiten example - mandelbrot</h2>
<iframe src="mandelbrot.content.html" width="640" height="640"></iframe>
<div class="card"><pre class="card-body"><code class="language-go">// &#43;build example jsgo
package main
import (
&#34;log&#34;
&#34;math&#34;
&#34;github.com/hajimehoshi/ebiten&#34;
)
const (
screenWidth = 640
screenHeight = 640
maxIt = 128
)
var (
offscreen *ebiten.Image
offscreenPix []byte
palette [maxIt]byte
)
func init() {
offscreen, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
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 &lt; screenHeight; j&#43;&#43; {
for i := 0; i &lt; screenHeight; i&#43;&#43; {
x := float64(i)*size/screenWidth - size/2 &#43; centerX
y := (screenHeight-float64(j))*size/screenHeight - size/2 &#43; centerY
c := complex(x, y)
z := complex(0, 0)
it := 0
for ; it &lt; maxIt; it&#43;&#43; {
z = z*z &#43; c
if real(z)*real(z)&#43;imag(z)*imag(z) &gt; 4 {
break
}
}
r, g, b := color(it)
p := 4 * (i &#43; j*screenWidth)
offscreenPix[p] = r
offscreenPix[p&#43;1] = g
offscreenPix[p&#43;2] = b
offscreenPix[p&#43;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, &#34;Mandelbrot (Ebiten Demo)&#34;); err != nil {
log.Fatal(err)
}
}
</code></pre></div>
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