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<!DOCTYPE html>
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< meta name = "description" content = "Ebiten example - sprites" >
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< title > Ebiten example - sprites< / title >
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< li class = "nav-item" > < a class = "nav-link" href = "https://github.com/hajimehoshi/ebiten" > GitHub< / a > < / li >
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< main > < div class = "container" >
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< h2 > Ebiten example - sprites< / h2 >
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< iframe src = "sprites.content.html" width = "640" height = "480" > < / iframe >
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< div class = "card" > < pre class = "card-body" > < code class = "language-go" > // + build example jsgo
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package main
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import (
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" bytes"
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" fmt"
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" image"
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_ " image/png"
" log"
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" math"
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" math/rand"
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" github.com/hajimehoshi/ebiten"
" github.com/hajimehoshi/ebiten/ebitenutil"
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" github.com/hajimehoshi/ebiten/examples/resources/images"
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)
const (
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screenWidth = 320
screenHeight = 240
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maxAngle = 256
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)
var (
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ebitenImage *ebiten.Image
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)
type Sprite struct {
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imageWidth int
imageHeight int
x int
y int
vx int
vy int
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angle int
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}
func (s *Sprite) Update() {
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s.x + = s.vx
s.y + = s.vy
if s.x < 0 {
s.x = -s.x
s.vx = -s.vx
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} else if screenWidth < = s.x+ s.imageWidth {
s.x = 2*(screenWidth-s.imageWidth) - s.x
s.vx = -s.vx
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}
if s.y < 0 {
s.y = -s.y
s.vy = -s.vy
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} else if screenHeight < = s.y+ s.imageHeight {
s.y = 2*(screenHeight-s.imageHeight) - s.y
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s.vy = -s.vy
}
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s.angle+ +
s.angle %= maxAngle
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}
type Sprites struct {
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sprites []*Sprite
num int
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}
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func (s *Sprites) Update() {
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for _, sprite := range s.sprites {
sprite.Update()
}
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}
const (
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MinSprites = 0
MaxSprites = 50000
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)
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var (
sprites = & Sprites{make([]*Sprite, MaxSprites), 500}
op = & ebiten.DrawImageOptions{}
)
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func init() {
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// Decode image from a byte slice instead of a file so that
// this example works in any working directory.
// If you want to use a file, there are some options:
// 1) Use os.Open and pass the file to the image decoder.
// This is a very regular way, but doesn' t work on browsers.
// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
// This works even on browsers.
// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
// This also works on browsers.
img, _, err := image.Decode(bytes.NewReader(images.Ebiten_png))
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if err != nil {
log.Fatal(err)
}
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origEbitenImage, _ := ebiten.NewImageFromImage(img, ebiten.FilterDefault)
w, h := origEbitenImage.Size()
ebitenImage, _ = ebiten.NewImage(w, h, ebiten.FilterNearest)
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op := & ebiten.DrawImageOptions{}
op.ColorM.Scale(1, 1, 1, 0.5)
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ebitenImage.DrawImage(origEbitenImage, op)
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for i := range sprites.sprites {
w, h := ebitenImage.Size()
x, y := rand.Intn(screenWidth-w), rand.Intn(screenHeight-h)
vx, vy := 2*rand.Intn(2)-1, 2*rand.Intn(2)-1
a := rand.Intn(maxAngle)
sprites.sprites[i] = & Sprite{
imageWidth: w,
imageHeight: h,
x: x,
y: y,
vx: vx,
vy: vy,
angle: a,
}
}
}
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func update(screen *ebiten.Image) error {
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// Decrease the nubmer of the sprites.
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if ebiten.IsKeyPressed(ebiten.KeyLeft) {
sprites.num -= 20
if sprites.num < MinSprites {
sprites.num = MinSprites
}
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}
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// Increase the nubmer of the sprites.
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if ebiten.IsKeyPressed(ebiten.KeyRight) {
sprites.num + = 20
if MaxSprites < sprites.num {
sprites.num = MaxSprites
}
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}
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sprites.Update()
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if ebiten.IsRunningSlowly() {
return nil
}
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// Draw each sprite.
// DrawImage can be called many many times, but in the implementation,
// the actual draw call to GPU is very few since these calls satisfy
// some conditions e.g. all the rendering sources and targets are same.
// For more detail, see:
// https://godoc.org/github.com/hajimehoshi/ebiten#Image.DrawImage
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w, h := ebitenImage.Size()
for i := 0; i < sprites.num; i+ + {
s := sprites.sprites[i]
op.GeoM.Reset()
op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
op.GeoM.Rotate(2 * math.Pi * float64(s.angle) / maxAngle)
op.GeoM.Translate(float64(w)/2, float64(h)/2)
op.GeoM.Translate(float64(s.x), float64(s.y))
screen.DrawImage(ebitenImage, op)
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}
msg := fmt.Sprintf(`FPS: %0.2f
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Num of sprites: %d
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Press < - or -> to change the number of sprites`, ebiten.CurrentFPS(), sprites.num)
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ebitenutil.DebugPrint(screen, msg)
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return nil
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}
func main() {
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, " Sprites (Ebiten Demo)" ); err != nil {
log.Fatal(err)
}
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}
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< / code > < / pre > < / div >
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< / div > < / main >
< footer > < div class = "container" >
< p > © 2013 Hajime Hoshi< / p >
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< p > Code is licensed under < a href = "https://github.com/hajimehoshi/ebiten/blob/master/LICENSE" > the Apache License 2.0< / a > .< / p >
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< p > The content of this page is licensed under < a href = "https://creativecommons.org/licenses/by/4.0/" > the Creative Commons Attribution 4.0 License< / a > .< / p >
< / div > < / footer >
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< script src = "../scripts/highlight.pack.js" > < / script >
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< script > hljs . initHighlightingOnLoad ( ) ; < / script >
