+
+
Ebiten example - life
+ +// +build example
+
+package main
+
+import (
+ "image"
+ "log"
+ "math/rand"
+ "time"
+
+ "github.com/hajimehoshi/ebiten"
+
+ "os"
+ "image/png"
+)
+
+var (
+ randSource = rand.NewSource(time.Now().UnixNano())
+ rnd = rand.New(randSource)
+)
+
+// World represents the game state
+type World struct {
+ area [][]bool
+}
+
+// NewWorld creates a new world
+func NewWorld(width, height int) *World {
+ world := World{}
+ world.area = makeArea(width, height)
+ return &world
+}
+
+// RandomSeed inits world with a random state
+func (w *World) RandomSeed(limit int) {
+ height := len(w.area)
+ width := len(w.area[0])
+
+ for i := 0; i < limit; i++ {
+ x := rnd.Intn(width)
+ y := rnd.Intn(height)
+ w.area[y][x] = true
+ }
+}
+
+// Progress game state by one tick
+func (w *World) Progress() {
+ height := len(w.area)
+ width := len(w.area[0])
+
+ next := makeArea(width, height)
+
+ for y := 0; y < height; y++ {
+ for x := 0; x < width; x++ {
+
+ pop := neighbourCount(w.area, x, y)
+ switch {
+ case pop < 2:
+ // rule 1. Any live cell with fewer than two live neighbours
+ // dies, as if caused by under-population.
+ next[y][x] = false
+
+ case (pop == 2 || pop == 3) && w.area[y][x]:
+ // rule 2. Any live cell with two or three live neighbours
+ // lives on to the next generation.
+ next[y][x] = true
+
+ case pop > 3:
+ // rule 3. Any live cell with more than three live neighbours
+ // dies, as if by over-population.
+ next[y][x] = false
+
+ case pop == 3:
+ // rule 4. Any dead cell with exactly three live neighbours
+ // becomes a live cell, as if by reproduction.
+ next[y][x] = true
+ }
+ }
+ }
+ w.area = next
+}
+
+// DrawImage paints current game state
+func (w *World) DrawImage(img *image.RGBA) {
+ height := len(w.area)
+ width := len(w.area[0])
+
+ for y := 0; y < height; y++ {
+ for x := 0; x < width; x++ {
+ pos := 4*y*width + 4*x
+ if w.area[y][x] {
+ img.Pix[pos] = 0xff
+ img.Pix[pos+1] = 0xff
+ img.Pix[pos+2] = 0xff
+ img.Pix[pos+3] = 0xff
+ } else {
+ img.Pix[pos] = 0
+ img.Pix[pos+1] = 0
+ img.Pix[pos+2] = 0
+ img.Pix[pos+3] = 0
+ }
+ }
+ }
+}
+
+// neighbourCount calculates the Moore neighborhood of x, y
+func neighbourCount(a [][]bool, x, y int) int {
+ height := len(a)
+ width := len(a[0])
+
+ lowX := 0
+ if x > 0 {
+ lowX = x - 1
+ }
+
+ lowY := 0
+ if y > 0 {
+ lowY = y - 1
+ }
+
+ highX := width - 1
+ if x < width-1 {
+ highX = x + 1
+ }
+
+ highY := height - 1
+ if y < height-1 {
+ highY = y + 1
+ }
+
+ near := 0
+ for pY := lowY; pY <= highY; pY++ {
+ for pX := lowX; pX <= highX; pX++ {
+ if !(pX == x && pY == y) && a[pY][pX] {
+ near++
+ }
+ }
+ }
+
+ return near
+}
+
+func makeArea(width, height int) [][]bool {
+ area := make([][]bool, height)
+ for i := 0; i < height; i++ {
+ area[i] = make([]bool, width)
+ }
+ return area
+}
+
+const (
+ screenWidth = 320
+ screenHeight = 240
+)
+
+var (
+ world *World
+ noiseImage *image.RGBA
+)
+
+func update(screen *ebiten.Image) error {
+ world.Progress()
+ world.DrawImage(noiseImage)
+ if err := screen.ReplacePixels(noiseImage.Pix); err != nil {
+ return err
+ }
+ if ebiten.IsKeyPressed(ebiten.KeyQ) {
+ f, err := os.Create("screenshot.png")
+ if err != nil {
+ return err
+ }
+ defer f.Close()
+ if err := png.Encode(f, screen); err != nil {
+ return err
+ }
+ os.Exit(0)
+ }
+ return nil
+}
+
+func main() {
+ population := int((screenWidth * screenHeight) / 10)
+ scale := 2.0
+
+ world = NewWorld(screenWidth, screenHeight)
+ world.RandomSeed(population)
+
+ noiseImage = image.NewRGBA(image.Rect(0, 0, screenWidth, screenHeight))
+ if err := ebiten.Run(update, screenWidth, screenHeight, scale, "Game of Life (Ebiten Demo)"); err != nil {
+ log.Fatal(err)
+ }
+}
+
