fixed accessing png files from disk every frame

community/go-jetpack/jetpack.go

@@ -88,15 +88,33 @@ func run() {
 	tilt := 0.01   // Default: 0.001
 	whichOn := false
 	onNumber := 0
-	jetpackName := "jetpack.png"
+	jetpackOffName := "jetpack.png"
+	jetpackOn1Name := "jetpack-on.png"
+	jetpackOn2Name := "jetpack-on2.png"
 	camVector := win.Bounds().Center()
 
 	bg, _ := loadSprite("sky.png")
 
+	// Jetpack - Rendering
+	jetpackOff, err := loadSprite(jetpackOffName)
+	if err != nil {
+		panic(err)
+	}
+	jetpackOn1, err := loadSprite(jetpackOn1Name)
+	if err != nil {
+		panic(err)
+	}
+	jetpackOn2, err := loadSprite(jetpackOn2Name)
+	if err != nil {
+		panic(err)
+	}
+
 	// Tutorial Text
 	txt := loadTTF("intuitive.ttf", 50, pixel.V(win.Bounds().Center().X-450, win.Bounds().Center().Y-200))
 	fmt.Fprintf(txt, "Explore the Skies with WASD or Arrow Keys!")
 
+	currentSprite := jetpackOff
+
 	// Game Loop
 	for !win.Closed() {
 		win.Update()
@@ -132,26 +150,20 @@ func run() {
 		if jetpackOn {
 			velY += jetAcc
 			whichOn = !whichOn
-			onNumber += 1
+			onNumber++
 			if onNumber == 5 { // every 5 frames, toggle anijetMation
 				onNumber = 0
 				if whichOn {
-					jetpackName = "jetpack-on.png"
+					currentSprite = jetpackOn1
 				} else {
-					jetpackName = "jetpack-on2.png"
+					currentSprite = jetpackOn2
 				}
 			}
 		} else {
-			jetpackName = "jetpack.png"
+			currentSprite = jetpackOff
 			velY -= gravity
 		}
 
-		// Jetpack - Rendering
-		jetpack, err := loadSprite(jetpackName)
-		if err != nil {
-			panic(err)
-		}
-
 		positionVector := pixel.V(win.Bounds().Center().X+jetX, win.Bounds().Center().Y+jetY-372)
 		jetMat := pixel.IM
 		jetMat = jetMat.Scaled(pixel.ZV, 4)
@@ -185,7 +197,7 @@ func run() {
 		bg.Draw(win, pixel.IM.Moved(pixel.V(win.Bounds().Center().X, win.Bounds().Center().Y+766)).Scaled(pixel.ZV, 10))
 		txt.Draw(win, pixel.IM)
 		win.SetSmooth(false)
-		jetpack.Draw(win, jetMat)
+		currentSprite.Draw(win, jetMat)
 
 	}