fractal.py

""" Computing Mandelbrot sets."""
import math

def mandel(real,imag):
    """ Compute a point in the Mandelbrot.

    The logarithm of number of iterations needed to
    determine whether a complex point is in the
    Mandelbrot set.

    Args:
        real : The real coordinate
        imag : The imaginary coordinate

    Returns:
        An integer in the range 1-255.
    """

    x = 0
    y = 0
    for i in range(1,257):
        if x * x + y * y > 4.0:
            break
        xt = real + x * x - y * y
        y = imag + 2.0 * x * y
        x = xt
    return int(math.log(i) * 256 / math.log(256)) - 1

def mandelbrot(size_x, size_y):
    """ Make an Mandelbrot set image.

    Args:
        size_x: Imag width
        size_y: Image height

    Returns:
        A list of lists of integers in the range 0-255.
    """
    return[[ mandel((3.5 * x / size_x) - 2.5,
                    (2.0 * y / size_y) - 1.0)
             for x in range(size_x)]
           for y in range(size_y)]