diff --git a/community/scrolling-background/README.md b/community/scrolling-background/README.md new file mode 100644 index 0000000..85e81cc --- /dev/null +++ b/community/scrolling-background/README.md @@ -0,0 +1,3 @@ +# Infinite scrolling background demo + +Created by [Sergio Vera](https://github.com/svera) diff --git a/community/scrolling-background/gamebackground.jpg b/community/scrolling-background/gamebackground.jpg new file mode 100644 index 0000000..e5eab2b Binary files /dev/null and b/community/scrolling-background/gamebackground.jpg differ diff --git a/community/scrolling-background/main.go b/community/scrolling-background/main.go new file mode 100644 index 0000000..9b402fa --- /dev/null +++ b/community/scrolling-background/main.go @@ -0,0 +1,77 @@ +package main + +import ( + "image" + "os" + + _ "image/jpeg" + + "github.com/faiface/pixel" + "github.com/faiface/pixel/pixelgl" +) + +func loadPicture(path string) (pixel.Picture, error) { + file, err := os.Open(path) + if err != nil { + return nil, err + } + defer file.Close() + img, _, err := image.Decode(file) + if err != nil { + return nil, err + } + return pixel.PictureDataFromImage(img), nil +} + +const ( + windowWidth = 300 + windowHeight = 225 +) + +func run() { + cfg := pixelgl.WindowConfig{ + Title: "Scrolling background demo", + Bounds: pixel.R(0, 0, windowWidth, windowHeight), + VSync: true, + } + win, err := pixelgl.NewWindow(cfg) + if err != nil { + panic(err) + } + + // Pic must have double the width of the window, as it will scroll to the left + pic, err := loadPicture("gamebackground.jpg") + if err != nil { + panic(err) + } + + // Backgrounds are made taking the left and right halves of the image + background1 := pixel.NewSprite(pic, pixel.R(0, 0, windowWidth, windowHeight)) + background2 := pixel.NewSprite(pic, pixel.R(windowWidth, 0, windowWidth*2, windowHeight)) + + // In the beginning, vector1 will put background1 filling the whole window, while vector2 will + // put background2 just at the right side of the window, out of view + vector1 := pixel.V(windowWidth/2, (windowHeight/2)+1) + vector2 := pixel.V(windowWidth+(windowWidth/2), (windowHeight/2)+1) + + i := float64(0) + for !win.Closed() { + // When one of the backgrounds has completely scrolled, we swap displacement vectors, + // so the backgrounds will swap positions too regarding the previous iteration, + // thus making the background look like infinite. + if i == -windowWidth { + i = 0 + vector1, vector2 = vector2, vector1 + } + // This delta vector will move the backgrounds to the left + d := pixel.V(-i, 0) + background1.Draw(win, pixel.IM.Moved(vector1.Sub(d))) + background2.Draw(win, pixel.IM.Moved(vector2.Sub(d))) + i-- + win.Update() + } +} + +func main() { + pixelgl.Run(run) +}