[ebiten/discussions/2461] fade normal

fade_normal.go

package main
import ( "time" ; "image" ; "image/color" )
import "github.com/hajimehoshi/ebiten/v2"

// Approach 2: use a small image and then scale its size too.

func init() { ebiten.SetWindowResizingMode(ebiten.WindowResizingModeEnabled) }
func main() { ebiten.RunGame(&Game{}) }
type Game struct { ticks int ; fade *ebiten.Image }
func (g *Game) Layout(w, h int) (int, int) { return w, h }
func (g *Game) Update() error { g.ticks++ ; return nil }
func (g *Game) Draw(screen *ebiten.Image) {
	// base content or pattern
	screen.Fill(color.White)

	// init fade image if uninitialized (could also be done on init)
	if g.fade == nil {
		img := ebiten.NewImage(3, 3)
		img.Fill(color.Black)
		g.fade = img.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
	}

	// apply fading
	fadingDuration := 5000*time.Millisecond // you may change this to test
	opts := &ebiten.DrawImageOptions{}
	opacity := float64(time.Second)*(float64(g.ticks)/float64(ebiten.TPS()))/float64(fadingDuration)
	if opacity > 1.0 { opacity = 1.0 }
	
	bounds := screen.Bounds()
	opts.GeoM.Scale(float64(bounds.Dx()), float64(bounds.Dy()))
	opts.ColorM.Translate(0, 0, 0, opacity - 1.0)
	screen.DrawImage(g.fade, opts)
}