ebiten/examples/alphablending/main.go

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// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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package main
import (
"image/color"
_ "image/png"
"log"
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"github.com/hajimehoshi/ebiten"
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"github.com/hajimehoshi/ebiten/ebitenutil"
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)
const (
screenWidth = 320
screenHeight = 240
)
var (
count int
ebitenImage *ebiten.Image
)
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type imageParts struct {
diff float64
}
func (p *imageParts) Src(i int) (int, int, int, int) {
w, h := ebitenImage.Size()
return 0, 0, w, h
}
func (p *imageParts) Dst(i int) (int, int, int, int) {
x := int(float64(i%10)*p.diff + 15)
y := int(float64(i/10)*p.diff + 20)
w, h := ebitenImage.Size()
return x, y, x + w, y + h
}
func (p *imageParts) Len() int {
return 10 * 10
}
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func update(screen *ebiten.Image) error {
count++
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count %= ebiten.FPS * 10
diff := float64(count) * 0.2
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switch {
case 480 < count:
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diff = 0
case 240 < count:
diff = float64(480-count) * 0.2
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}
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if err := screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff}); err != nil {
return err
}
op := &ebiten.DrawImageOptions{}
op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
op.ImageParts = &imageParts{
diff: diff,
}
if err := screen.DrawImage(ebitenImage, op); err != nil {
return err
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}
return nil
}
func main() {
var err error
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ebitenImage, _, err = ebitenutil.NewImageFromFile("_resources/images/ebiten.png", ebiten.FilterNearest)
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if err != nil {
log.Fatal(err)
}
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Alpha Blending (Ebiten Demo)"); err != nil {
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log.Fatal(err)
}
}