Ebiten example - alphablending

// +build example

package main

import (
        "image/color"
        _ "image/png"
        "log"

        "github.com/hajimehoshi/ebiten"
        "github.com/hajimehoshi/ebiten/ebitenutil"
)

const (
        screenWidth  = 320
        screenHeight = 240
)

var (
        count       int
        ebitenImage *ebiten.Image
)

func update(screen *ebiten.Image) error {
        count++
        count %= ebiten.FPS * 10
        diff := float64(count) * 0.2
        switch {
        case 480 < count:
                diff = 0
        case 240 < count:
                diff = float64(480-count) * 0.2
        }
        if ebiten.IsRunningSlowly() {
                return nil
        }
        screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff})
        op := &ebiten.DrawImageOptions{}
        op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
        for i := 0; i < 10*10; i++ {
                op.GeoM.Reset()
                x := float64(i%10)*diff + 15
                y := float64(i/10)*diff + 20
                op.GeoM.Translate(x, y)
                screen.DrawImage(ebitenImage, op)
        }
        return nil
}

func main() {
        var err error
        ebitenImage, _, err = ebitenutil.NewImageFromFile("_resources/images/ebiten.png", ebiten.FilterNearest)
        if err != nil {
                log.Fatal(err)
        }
        if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Alpha Blending (Ebiten Demo)"); err != nil {
                log.Fatal(err)
        }
}