DragonCurve.py

import math
import matplotlib.pyplot as plt

Pi = math.pi
max_depth = 10

save_img_fname = "DragonCurve_depth{}.png".format(max_depth)

def get_rotate_coordinate(x, y, Cx, Cy, theta=Pi/2):
    newx = x*math.cos(theta)-y*math.sin(theta)+Cx-Cx*math.cos(theta)+Cy*math.sin(theta)
    newy = x*math.sin(theta)+y*math.cos(theta)+Cy-Cx*math.sin(theta)-Cy*math.cos(theta)
    return newx, newy

def draw(xs, ys):
    plt.plot(xs,ys)
    plt.axis("off")
    plt.savefig(save_img_fname)
    plt.show()

def main():
    # Initial Condition
    xs = [1, 0]
    ys = [1, 1]

    for depth in range(max_depth):
        for k in range(2**depth):
            newx, newy = get_rotate_coordinate(xs[2**depth-k-1], ys[2**depth-k-1], Cx=xs[2**depth], Cy=ys[2**depth])
            xs.append(newx)
            ys.append(newy)
        print("depth:{} length:{}".format(depth, len(xs)-1))
    
    print("drawing..")
    draw(xs, ys)

if __name__ == "__main__":
    main()