[FIXED] Numpy – place small array at coordinate in large array?

Issue

I have the following 2D-numpy array:

matrix = np.zeros((250, 250))

Now, at various coordinates, I want to replace not just the coordinate value but its local vicinity too with a smaller array. As exemplary replacement we can take a diamond:

import skimage.morphology
star = skimage.morphology.diamond(3)  # small array / replacement

coords_r = np.random.randint(0, 250, 20)  # row coordinates
coords_c = np.random.randint(0, 250, 20)  # column coordinates

I came up with the following rather sloppy way and was wondering if there was a simpler / more elegant solution. Furthermore, this method will overwrite if two objects are close enough:

max_r, max_c = matrix.shape
obj = star
half_obj = int((star.shape[0])/2)

for r, c in zip(coords_r, coords_c):
    
    curr_obj = obj
    start_r = r-half_obj-1
    end_r = r+half_obj
    start_c = c-half_obj-1
    end_c = c+half_obj
    
    # Check if on corners
    if r-half_obj-1 < 0:
        start_r = 0
        curr_obj = curr_obj[-r:, :]
    if r+half_obj > matrix.shape[0]:
        end_r = max_r
        curr_obj = curr_obj[:max_r-start_r, :]
    if c-half_obj-1 < 0:
        start_c = 0
        curr_obj = curr_obj[:, -c:]
    if c+half_obj > matrix.shape[1]:
        end_c = max_c
        curr_obj = curr_obj[:, :max_c-start_c]
        
    matrix[start_r:end_r, start_c:end_c] = curr_obj

Thanks in advance.

Solution

I asked similar question some time ago: Add small image to the canvas as numpy arrays

Here is my solution to your problem:

matrix_size = 250
star_size = 3

matrix = np.ones((matrix_size, matrix_size))
star = 1 - skimage.morphology.diamond(star_size)

coords_r = np.random.randint(0, matrix_size, 20)  # row coordinates
coords_c = np.random.randint(0, matrix_size, 20)  # column coordinates

for r, c in zip(coords_r, coords_c):
    matrix[max(r - star_size, 0):r + star_size + 1, max(c - star_size, 0):c + star_size + 1] *= star[max(star_size - r, 0):star_size + matrix_size - r, max(star_size - c, 0):star_size + matrix_size - c]
matrix = 1-matrix

And this is what I get:

Answered By - Fallen Apart