basic_julia.py

"""
julia.py
Define a mapping from (x, y) pixel locations to (R,G,B) colour values by
counting iterations to form a Julia set.
"""
import sys
from colorsys import hsv_to_rgb

from config import MAX_X, MAX_Y, MAX_ITERATION, X1, X2, Y1, Y2, C
from utils import progress, scaled
from julia_iterations import iterations as count_its


def color(it):
    """
    Arbitrarily maps the number of iterations to an RGB colour.
    :param it:The number of iterations for this value.
    :return:A tuple (R, G, B) of color values to paint this pixel.
    """
    # TODO: Figure out a linear colour-map that looks half-decent.
    h = it/MAX_ITERATION
    return tuple(int(i*100) for i in hsv_to_rgb(h, 0.8, 1))


@progress(iterations=MAX_X * MAX_Y)
def basic_julia(x, y):
    """
    Calculate and return the RGB colour for a given (x, y) pixel.
    :param x: The X coordinate of the pixel.
    :param y: The Y coordinate of the pixel.
    :return: A tuple (R,G,B) of values 0-255.
    """
    # Scale X and Y to the viewport bounded by (X1, Y1) and (X2, Y2).
    x = scaled(x, 0, MAX_Y, X1, X2)
    y = scaled(y, 0, MAX_Y, Y1, Y2)

    # Count the number of iterations to escape an arbitrary "bound".
    cr, ci = C
    i = count_its(x, y, cr, ci, MAX_ITERATION)

    # Return a color based on this escape time.
    if i == MAX_ITERATION:
        return 0, 0, 0
    return color(i)


if __name__ == "__main__":
    from renderer import render
    filename = "julia.png"
    if "-o" in sys.argv:
        filename = sys.argv[-1]
    render(basic_julia, filename)