78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
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package main
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import (
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"image"
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"os"
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_ "image/jpeg"
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"github.com/faiface/pixel"
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"github.com/faiface/pixel/pixelgl"
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)
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func loadPicture(path string) (pixel.Picture, error) {
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file, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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img, _, err := image.Decode(file)
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if err != nil {
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return nil, err
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}
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return pixel.PictureDataFromImage(img), nil
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}
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const (
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windowWidth = 300
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windowHeight = 225
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)
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func run() {
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cfg := pixelgl.WindowConfig{
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Title: "Scrolling background demo",
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Bounds: pixel.R(0, 0, windowWidth, windowHeight),
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VSync: true,
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}
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win, err := pixelgl.NewWindow(cfg)
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if err != nil {
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panic(err)
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}
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// Pic must have double the width of the window, as it will scroll to the left
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pic, err := loadPicture("gamebackground.jpg")
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if err != nil {
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panic(err)
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}
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// Backgrounds are made taking the left and right halves of the image
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background1 := pixel.NewSprite(pic, pixel.R(0, 0, windowWidth, windowHeight))
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background2 := pixel.NewSprite(pic, pixel.R(windowWidth, 0, windowWidth*2, windowHeight))
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// In the beginning, vector1 will put background1 filling the whole window, while vector2 will
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// put background2 just at the right side of the window, out of view
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vector1 := pixel.V(windowWidth/2, (windowHeight/2)+1)
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vector2 := pixel.V(windowWidth+(windowWidth/2), (windowHeight/2)+1)
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i := float64(0)
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for !win.Closed() {
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// When one of the backgrounds has completely scrolled, we swap displacement vectors,
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// so the backgrounds will swap positions too regarding the previous iteration,
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// thus making the background look like infinite.
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if i == -windowWidth {
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i = 0
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vector1, vector2 = vector2, vector1
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}
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// This delta vector will move the backgrounds to the left
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d := pixel.V(-i, 0)
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background1.Draw(win, pixel.IM.Moved(vector1.Sub(d)))
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background2.Draw(win, pixel.IM.Moved(vector2.Sub(d)))
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i--
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win.Update()
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}
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}
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func main() {
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pixelgl.Run(run)
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}
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