| import cairo | |
| """ | |
| Created on Wed Dec 27 19:29:20 2017 | |
| To summarize, here is how to draw a Sierpinski gasket in a square: | |
| Determine how small the square is. If it's small enough to be a base case, | |
| then just fill in the square. You get to pick how small "small enough" is. | |
| Otherwise, divide the square into upper left, upper right, lower right, and | |
| lower left squares. Recursively "solve" three subproblems: | |
| 1. Draw a Sierpinski gasket in the upper left square. | |
| 2. Draw a Sierpinski gasket in the upper right square. | |
| 3. Draw a Sierpinski gasket in the lower right square. | |
| You need to make not just one, but three recursive calls. | |
| That is why we consider drawing a Sierpinski gasket to exhibit multiple recursion. | |
| """ | |
| ''' | |
| draws a diagonal where vertexes represent a tuple of coordinates (x,y) | |
| ''' | |
| def draw_diagonals(vertex_a, vertex_b, vertex_c, vertex_d, context): | |
| context.move_to(vertex_b) | |
| context.line_to(vertex_c) | |
| context.close_path() | |
| context.move_to(vertex_d) | |
| context.line_to(vertex_a) | |
| context.close_path() | |
| #where (0,0) is the starting point | |
| def draw_sierpinksi(length_square, context, vertex_a, vertex_b, vertex_c, vertex_d,): | |
| if length_square == 1: | |
| context.set_source_rgb(0, 0, 0) | |
| context.fill() | |
| midpoint = length_square/2 | |
| # move to midpoint of top line | |
| context.set_source_rgba(1, 0.2, 0.2, 0.6) | |
| context.set_line_width(0.02) | |
| context.move_to(midpoint, 0) | |
| context.line_to(-midpoint*2, midpoint) | |
| context.move_to(0, -midpoint) | |
| context.line_to(-midpoint*2, midpoint) | |
| context.move_to(vertex_b) | |
| context.line_to(vertex_c) | |
| context.move_to(vertex_d) | |
| context.line_to(vertex_a) | |
| #offset = midpoint | |
| #starting_pt = (0, 0) | |
| draw_sierpinksi(length_square - 2, context, (0, 0 + midpoint), (midpoint, 0), (0, -midpoint), (midpoint, -midpoint)) # upper left | |
| draw_sierpinksi(length_square - 2, context, (midpoint*2, 0), (midpoint, 0), (midpoint*2, -midpoint), (midpoint, -midpoint)) # upper right share b,d from upperleft | |
| draw_sierpinksi(length_square - 2, context, (-midpoint*2, -midpoint*2), (midpoint*2, -midpoint),(midpoint*2, -midpoint), (midpoint, -midpoint)) #lower right share c,d upperright | |
| if __name__ == '__main__': | |
| width, height = 256, 256 | |
| surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, width, height) | |
| context = cairo.Context (surface) | |
| width_square = 250 | |
| context.rectangle(0, 0, width_square, width_square ) | |