Draw "Draw Ferns Programmatically" in Python

Taking advantage of the "Drawing ferns programmatically" series, I wrote it in Python as well.

• Draw ferns programmatically-Proceed with high heat
• Draw "Draw ferns programmatically" with Dart --Qiita
• Draw "Draw ferns programmatically" with Go --Qiita
• Clojure-Drawing ferns programmatically-Qiita

Output result

Source code

Recursive call version

• A recursive call version similar to the original.
• I wrote it neatly using lambda in the function definition.
• Requires Image Library PIL (Python Imaging Library) or Pillow.

import random

N = 20
xm = 0
ym = 0.5
h = 0.6

width = 500
height = 500

W1x = lambda x, y: 0.836 * x + 0.044 * y
W1y = lambda x, y: -0.044 * x + 0.836 * y + 0.169
W2x = lambda x, y: -0.141 * x + 0.302 * y
W2y = lambda x, y: 0.302 * x + 0.141 * y + 0.127
W3x = lambda x, y: 0.141 * x - 0.302 * y
W3y = lambda x, y: 0.302 * x + 0.141 * y + 0.169
W4x = lambda x, y: 0
W4y = lambda x, y: 0.175337 * y

def f(im, k, x, y):
    if 0 < k:
        f(im, k - 1, W1x(x, y), W1y(x, y))
        if random.random() < 0.3:
            f(im, k - 1, W2x(x, y), W2y(x, y))
        if random.random() < 0.3:
            f(im, k - 1, W3x(x, y), W3y(x, y))
        if random.random() < 0.3:
            f(im, k - 1, W4x(x, y), W4y(x, y))
    else:
        s = 490
        im.putpixel((int(x * s + width * 0.5), int(height - y * s)), (0, 128, 0))

if __name__ == '__main__':
    from PIL import Image
    im = Image.new("RGB", (width, height), (255, 255, 255))
    f(im, N, 0, 0)
    im.show()

This is a bit unattractive because I have to pass image-related arguments with the function f () and write drawing logic inside the function, so I tried to make it a little more Pythonic.

Recursive call + generator version

• The generator is used to return the result of the recursive call as yield.
• The drawing logic was able to get out of the function f ().

import random

N = 20
xm = 0
ym = 0.5
h = 0.6

width = 500
height = 500

W1x = lambda x, y: 0.836 * x + 0.044 * y
W1y = lambda x, y: -0.044 * x + 0.836 * y + 0.169
W2x = lambda x, y: -0.141 * x + 0.302 * y
W2y = lambda x, y: 0.302 * x + 0.141 * y + 0.127
W3x = lambda x, y: 0.141 * x - 0.302 * y
W3y = lambda x, y: 0.302 * x + 0.141 * y + 0.169
W4x = lambda x, y: 0
W4y = lambda x, y: 0.175337 * y

def f(k, x, y):
    if 0 < k:
        for p in f(k - 1, W1x(x, y), W1y(x, y)):
            yield p
        if random.random() < 0.3:
            for p in f(k - 1, W2x(x, y), W2y(x, y)):
                yield p
        if random.random() < 0.3:
            for p in f(k - 1, W3x(x, y), W3y(x, y)):
                yield p
        if random.random() < 0.3:
            for p in f(k - 1, W4x(x, y), W4y(x, y)):
                yield p
    else:
        s = 490
        yield x * s + width * 0.5, height - y * s

if __name__ == '__main__':
    from PIL import Image
    im = Image.new("RGB", (width, height), (255, 255, 255))
    for p in f(N, 0, 0):
        im.putpixel((int(p[0]), int(p[1])), (0, 128, 0))
    im.show()

Summary

• Recursive call + generator combination technique
• Separate drawing logic and coordinate calculation logic
• I like generators that can be written lightly with yield.