circular_gradient.py

import math

center_x, center_y = shape[1] // 2, shape[0] // 2
circle_grad = np.zeros_like(world)

for y in range(world.shape[0]):
    for x in range(world.shape[1]):
        distx = abs(x - center_x)
        disty = abs(y - center_y)
        dist = math.sqrt(distx*distx + disty*disty)
        circle_grad[y][x] = dist

# get it between -1 and 1
max_grad = np.max(circle_grad)
circle_grad = circle_grad / max_grad
circle_grad -= 0.5
circle_grad *= 2.0
circle_grad = -circle_grad

# shrink gradient
for y in range(world.shape[0]):
    for x in range(world.shape[1]):
        if circle_grad[y][x] > 0:
            circle_grad[y][x] *= 20

# get it between 0 and 1
max_grad = np.max(circle_grad)
circle_grad = circle_grad / max_grad

toimage(circle_grad).show()