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go_book/lissajous/go.mod

@@ -0,0 +1,3 @@
+module lissajous
+
+go 1.24.5

go_book/lissajous/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/gif"
+	"io"
+	"math"
+	"math/rand"
+	"os"
+	"time"
+)
+
+var palette = []color.Color{color.White,color.Black}
+
+const (
+	whiteIndex = 0
+	blackIndex = 1
+)
+
+func main() {
+	lissajous(os.Stdout)
+}
+
+func lissajous(out io.Writer) { 
+	const (
+		cycles = 5
+		res = 0.001
+		size = 100
+		nframes = 64
+		delay = 8
+	)
+
+	rand.Seed(time.Now().UTC().UnixNano())
+	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)
+}