ebiten/docs/examples/paint.html
2018-02-14 03:00:08 +09:00

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<h2>Ebiten example - paint</h2>
<iframe src="paint.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;fmt&#34;
&#34;image&#34;
&#34;image/color&#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 (
count int
brushImage *ebiten.Image
canvasImage *ebiten.Image
)
func init() {
const (
a0 = 0x40
a1 = 0xc0
a2 = 0xff
)
pixels := []uint8{
a0, a1, a1, a0,
a1, a2, a2, a1,
a1, a2, a2, a1,
a0, a1, a1, a0,
}
brushImage, _ = ebiten.NewImageFromImage(&amp;image.Alpha{
Pix: pixels,
Stride: 4,
Rect: image.Rect(0, 0, 4, 4),
}, ebiten.FilterDefault)
canvasImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
canvasImage.Fill(color.White)
}
// paint draws the brush on the given canvas image at the position (x, y).
func paint(canvas *ebiten.Image, x, y int) {
op := &amp;ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(x), float64(y))
// Scale the color and rotate the hue so that colors vary on each frame.
op.ColorM.Scale(1.0, 0.50, 0.125, 1.0)
theta := 2.0 * math.Pi * float64(count%ebiten.FPS) / ebiten.FPS
op.ColorM.RotateHue(theta)
canvas.DrawImage(brushImage, op)
}
func update(screen *ebiten.Image) error {
drawn := false
// Paint the brush by mouse dragging
mx, my := ebiten.CursorPosition()
if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
paint(canvasImage, mx, my)
drawn = true
}
// Paint the brush by touches
for _, t := range ebiten.Touches() {
x, y := t.Position()
paint(canvasImage, x, y)
drawn = true
}
if drawn {
count&#43;&#43;
}
if ebiten.IsRunningSlowly() {
return nil
}
screen.DrawImage(canvasImage, nil)
msg := fmt.Sprintf(&#34;(%d, %d)&#34;, mx, my)
for _, t := range ebiten.Touches() {
x, y := t.Position()
msg &#43;= fmt.Sprintf(&#34;\n(%d, %d) touch %d&#34;, x, y, t.ID())
}
ebitenutil.DebugPrint(screen, msg)
return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, &#34;Paint (Ebiten Demo)&#34;); err != nil {
log.Fatal(err)
}
}
</code></pre></div>
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