warp.py

import cairocffi as cairo
import numpy as np
import random

def random_coefs(order, sigma):
    return [random.gauss(0, sigma) for _ in range(order)]

def random_transform():
    y_dx = random_coefs(5, 0.3)
    y_dy = random_coefs(5, 0.3)
    x_angle = random_coefs(5, 0.5)
    x_dx = random_coefs(5, 0.3)
    x_dy = random_coefs(5, 0.3)
    def transform(x, y):
        a = np.polyval(x_angle, x)
        dx = np.polyval(x_dx, x)
        dy = np.polyval(x_dy, x)
        s = np.sin(a)
        c = np.cos(a)
        x += np.polyval(y_dx, y)
        y += np.polyval(y_dy, y)
        tx = c * x - s * y + dx
        ty = c * y + s * x + dy
        return (tx, ty)
    return transform

def draw_one(cr, bx0, by0, bx1, by1):
    n = 100
    transform = random_transform()

    points = {}
    for y in range(-n, n+1):
        for x in range(-n, n+1):
            tx, ty = transform(x / n, y / n)
            points[(x, y)] = (tx, ty)

    x0 = min(x for x, y in points.values())
    x1 = max(x for x, y in points.values())
    y0 = min(y for x, y in points.values())
    y1 = max(y for x, y in points.values())
    dx = x1 - x0
    dy = y1 - y0
    sx = (bx1 - bx0) / dx
    sy = (by1 - by0) / dy
    s = min(sx, sy) * 0.75
    cx = (x0 + x1) / 2
    cy = (y0 + y1) / 2
    cr.identity_matrix()
    cr.translate((bx0 + bx1) / 2, (by0 + by1) / 2)
    cr.scale(s)
    cr.translate(-cx, -cy)

    for i in range(-n, n):
        for j in range(-n, n+1, 10):
            cr.move_to(*points[(j, i+0)])
            cr.line_to(*points[(j, i+1)])
            cr.move_to(*points[(i+0, j)])
            cr.line_to(*points[(i+1, j)])
    cr.set_line_width(2 / s)
    cr.set_source_rgb(0, 0, 0)
    cr.stroke()

    cr.set_source_rgba(0, 0, 0, 0.25)
    for y in range(-n, n):
        for x in range(-n, n):
            cr.move_to(*points[(x+0, y+0)])
            cr.line_to(*points[(x+1, y+0)])
            cr.line_to(*points[(x+1, y+1)])
            cr.line_to(*points[(x+0, y+1)])
            cr.close_path()
            cr.fill()

def main():
    w = h = 1600
    surface = cairo.ImageSurface(cairo.FORMAT_RGB24, w, h)
    cr = cairo.Context(surface)
    cr.set_source_rgb(1, 1, 1)
    cr.paint()
    draw_one(cr, 0, 0, w, h)
    surface.write_to_png('out.png')

if __name__ == '__main__':
    main()