init

lisajous/lisajous.go

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+// Lisajous generates GIF animations of random Lisajous figures.
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/gif"
+	"io"
+	"math"
+	"math/rand"
+	"os"
+)
+
+var palette = [] color.Color{color.White, color.Black}
+
+const (
+	whiteIndex = 0
+	blackindex = 1
+)
+
+func main() {
+	lisajous(os.Stdout)
+}
+
+func lisajous(out io.Writer) {
+	const (
+		cycles = 5
+		res = 0.001
+		size = 100
+		nframes = 64
+		delay = 8
+	)
+	freq := rand.Float64() * 3.0
+	anim := gif.GIF{LoopCount: nframes}
+	phase := 0.0
+	for i := 0; i < nframes; i++ {
+		rect := image.Rect(0, 0, 2*size+1, 2*size+1)
+		img := image.NewPaletted(rect, palette)
+		for t := 0.0; t < cycles*2*math.Pi; t += res {
+			x := math.Sin(t)
+			y := math.Sin(t*freq + phase)
+			img.SetColorIndex(size+int(x*size+0.5), size+int(y*size+0.5), blackindex)
+		}
+		phase += 0.1
+		anim.Delay = append(anim.Delay, delay)
+		anim.Image = append(anim.Image, img)
+	}
+	gif.EncodeAll(out, &anim)
+}