Task: Dragon curve




Go: package main

import (
    "fmt"
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "math"
    "os"
)



const sep = 512

const depth = 14

var s = math.Sqrt2 / 2
var sin = []float64{0, s, 1, s, 0, -s, -1, -s}
var cos = []float64{1, s, 0, -s, -1, -s, 0, s}
var p = color.NRGBA{64, 192, 96, 255}
var b *image.NRGBA

func main() {
    width := sep * 11 / 6
    height := sep * 4 / 3
    bounds := image.Rect(0, 0, width, height)
    b = image.NewNRGBA(bounds)
    draw.Draw(b, bounds, image.NewUniform(color.White), image.ZP, draw.Src)
    dragon(14, 0, 1, sep, sep/2, sep*5/6)
    f, err := os.Create("dragon.png")
    if err != nil {
        fmt.Println(err)
        return
    }
    if err = png.Encode(f, b); err != nil {
        fmt.Println(err)
    }
    if err = f.Close(); err != nil {
        fmt.Println(err)
    }
}

func dragon(n, a, t int, d, x, y float64) {
    if n <= 1 {
        
        
        
        
        x1 := int(x + .5)
        y1 := int(y + .5)
        x2 := int(x + d*cos[a] + .5)
        y2 := int(y + d*sin[a] + .5)
        xInc := 1
        if x1 > x2 {
            xInc = -1
        }
        yInc := 1
        if y1 > y2 {
            yInc = -1
        }
        for x, y := x1, y1; ; x, y = x+xInc, y+yInc {
            b.Set(x, y, p)
            if x == x2 {
                break
            }
        }
        return
    }
    d *= s
    a1 := (a - t) & 7
    a2 := (a + t) & 7
    dragon(n-1, a1, 1, d, x, y)
    dragon(n-1, a2, -1, d, x+d*cos[a1], y+d*sin[a1])
}


Java: import java.awt.Color;
import java.awt.Graphics;
import java.util.*;
import javax.swing.JFrame;

public class DragonCurve extends JFrame {

    private List<Integer> turns;
    private double startingAngle, side;

    public DragonCurve(int iter) {
        super("Dragon Curve");
        setBounds(100, 100, 800, 600);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        turns = getSequence(iter);
        startingAngle = -iter * (Math.PI / 4);
        side = 400 / Math.pow(2, iter / 2.);
    }

    public List<Integer> getSequence(int iterations) {
        List<Integer> turnSequence = new ArrayList<Integer>();
        for (int i = 0; i < iterations; i++) {
            List<Integer> copy = new ArrayList<Integer>(turnSequence);
            Collections.reverse(copy);
            turnSequence.add(1);
            for (Integer turn : copy) {
                turnSequence.add(-turn);
            }
        }
        return turnSequence;
    }

    @Override
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        double angle = startingAngle;
        int x1 = 230, y1 = 350;
        int x2 = x1 + (int) (Math.cos(angle) * side);
        int y2 = y1 + (int) (Math.sin(angle) * side);
        g.drawLine(x1, y1, x2, y2);
        x1 = x2;
        y1 = y2;
        for (Integer turn : turns) {
            angle += turn * (Math.PI / 2);
            x2 = x1 + (int) (Math.cos(angle) * side);
            y2 = y1 + (int) (Math.sin(angle) * side);
            g.drawLine(x1, y1, x2, y2);
            x1 = x2;
            y1 = y2;
        }
    }

    public static void main(String[] args) {
        new DragonCurve(14).setVisible(true);
    }
}