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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// +build example jsgo
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package main
import (
"bytes"
"image"
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"image/color"
_ "image/png"
"log"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/examples/resources/images"
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)
const (
screenWidth = 320
screenHeight = 240
)
var (
ebitenImage *ebiten.Image
)
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type Game struct {
count int
}
func (g *Game) Update(screen *ebiten.Image) error {
g.count++
g.count %= ebiten.MaxTPS() * 10
return nil
}
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func (g *Game) offset() float64 {
v := float64(g.count) * 0.2
switch {
case 480 < g.count:
v = 0
case 240 < g.count:
v = float64(480-g.count) * 0.2
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}
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return v
}
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func (g *Game) Draw(screen *ebiten.Image) {
screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff})
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// Draw 100 Ebitens
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v := g.offset()
op := &ebiten.DrawImageOptions{}
op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
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for i := 0; i < 10*10; i++ {
op.GeoM.Reset()
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x := float64(i%10)*v + 15
y := float64(i/10)*v + 20
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op.GeoM.Translate(x, y)
screen.DrawImage(ebitenImage, op)
}
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}
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
func main() {
// Decode image from a byte slice instead of a file so that
// this example works in any working directory.
// If you want to use a file, there are some options:
// 1) Use os.Open and pass the file to the image decoder.
// This is a very regular way, but doesn't work on browsers.
// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
// This works even on browsers.
// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
// This also works on browsers.
img, _, err := image.Decode(bytes.NewReader(images.Ebiten_png))
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if err != nil {
log.Fatal(err)
}
ebitenImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
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ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
ebiten.SetWindowTitle("Alpha Blending (Ebiten Demo)")
if err := ebiten.RunGame(&Game{}); err != nil {
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log.Fatal(err)
}
}