Data commit

Task/Chaos-game/Go/chaos-game.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"image/draw"
+	"image/gif"
+	"log"
+	"math"
+	"math/rand"
+	"os"
+	"time"
+)
+
+var bwPalette = color.Palette{
+	color.Transparent,
+	color.White,
+	color.RGBA{R: 0xff, A: 0xff},
+	color.RGBA{G: 0xff, A: 0xff},
+	color.RGBA{B: 0xff, A: 0xff},
+}
+
+func main() {
+	const (
+		width          = 160
+		frames         = 100
+		pointsPerFrame = 50
+		delay          = 100 * time.Millisecond
+		filename       = "chaos_anim.gif"
+	)
+
+	var tan60 = math.Sin(math.Pi / 3)
+	height := int(math.Round(float64(width) * tan60))
+	b := image.Rect(0, 0, width, height)
+	vertices := [...]image.Point{
+		{0, height}, {width, height}, {width / 2, 0},
+	}
+
+	// Make a filled triangle.
+	m := image.NewPaletted(b, bwPalette)
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		bg := int(math.Round(float64(b.Max.Y-y) / 2 / tan60))
+		for x := b.Min.X + bg; x < b.Max.X-bg; x++ {
+			m.SetColorIndex(x, y, 1)
+		}
+	}
+
+	// Pick starting point
+	var p image.Point
+	rand.Seed(time.Now().UnixNano())
+	p.Y = rand.Intn(height) + b.Min.Y
+	p.X = rand.Intn(width) + b.Min.X // TODO: make within triangle
+
+	anim := newAnim(frames, delay)
+	addFrame(anim, m)
+	for i := 1; i < frames; i++ {
+		for j := 0; j < pointsPerFrame; j++ {
+			// Pick a random vertex
+			vi := rand.Intn(len(vertices))
+			v := vertices[vi]
+			// Move p halfway there
+			p.X = (p.X + v.X) / 2
+			p.Y = (p.Y + v.Y) / 2
+			m.SetColorIndex(p.X, p.Y, uint8(2+vi))
+		}
+		addFrame(anim, m)
+	}
+	if err := writeAnim(anim, filename); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("wrote to %q\n", filename)
+}
+
+// Stuff for making a simple GIF animation.
+
+func newAnim(frames int, delay time.Duration) *gif.GIF {
+	const gifDelayScale = 10 * time.Millisecond
+	g := &gif.GIF{
+		Image: make([]*image.Paletted, 0, frames),
+		Delay: make([]int, 1, frames),
+	}
+	g.Delay[0] = int(delay / gifDelayScale)
+	return g
+}
+func addFrame(anim *gif.GIF, m *image.Paletted) {
+	b := m.Bounds()
+	dst := image.NewPaletted(b, m.Palette)
+	draw.Draw(dst, b, m, image.ZP, draw.Src)
+	anim.Image = append(anim.Image, dst)
+	if len(anim.Delay) < len(anim.Image) {
+		anim.Delay = append(anim.Delay, anim.Delay[0])
+	}
+}
+func writeAnim(anim *gif.GIF, filename string) error {
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	err = gif.EncodeAll(f, anim)
+	if cerr := f.Close(); err == nil {
+		err = cerr
+	}
+	return err
+}