# -*- coding: utf-8 -*- """ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A Simple Random Fractal Tree ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ """ import numpy as np try: import cairocffi as cairo except ImportError: import cairo ITERATIONS = 16 # total number of iterations ROOT_COLOR = np.array([0.0, 0.0, 0.0]) # root branch color LEAF_COLOR = np.array([1.0, 1.0, 0.2]) # leaf color TRUNK_LEN = 200 # initial length of the trunk TRUNK_RAD = 3.0 # initial radius of the trunk THETA = np.pi / 2 # initial angle of the branch ANGLE = np.pi / 4.5 # angle between branches in the same level PERTURB = 6.0 # perturb the angle a little to make the tree look random RATIO = 0.8 # contraction factor between successive trunks WIDTH = 600 # image width HEIGHT = 600 # image height ROOT = (WIDTH / 2.0, HEIGHT + 50) # pixel position of the root def get_color(level): """ Return an interpolation of the two colors `ROOT_COLOR` and `LEAF_COLOR`. """ a = float(level) / ITERATIONS return a * ROOT_COLOR + (1 - a) * LEAF_COLOR def get_line_width(level): """Return the line width of a given level.""" return max(1, TRUNK_RAD * level / ITERATIONS) def fractal_tree(ctx, # a cairo context to draw on level, # current level in the iterations start, # (x, y) coordinates of the start of this trunk t, # current trunk length r, # factor to contract the trunk in each iteration theta, # orientation of current trunk angle, # angle between branches in the same level perturb, # perturb the angle ): if level == 0: return x0, y0 = start # randomize the length randt = np.random.random() * t x, y = x0 + randt * np.cos(theta), y0 - randt * np.sin(theta) color = get_color(level) ctx.move_to(x0, y0) ctx.line_to(x, y) ctx.set_line_width(get_line_width(level)) ctx.set_source_rgb(*color) ctx.stroke() theta1 = theta + np.random.random() * (perturb / level) * angle theta2 = theta - np.random.random() * (perturb / level) * angle # recursively draw the next branches fractal_tree(ctx, level - 1, (x, y), t * r, r, theta1, angle, perturb) fractal_tree(ctx, level - 1, (x, y), t * r, r, theta2, angle, perturb) def main(): surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, WIDTH, HEIGHT) ctx = cairo.Context(surface) ctx.set_line_cap(cairo.LINE_CAP_ROUND) ctx.set_line_join(cairo.LINE_JOIN_ROUND) ctx.set_source_rgb(1, 1, 1) ctx.paint() fractal_tree(ctx, ITERATIONS, ROOT, TRUNK_LEN, RATIO, THETA, ANGLE, PERTURB) surface.write_to_png("random_fractal_tree.png") if __name__ == "__main__": main()