Slow calculating sum of individual cells of matrix

Question

I have a 3-D array in numpy, of dimensions 3000 x 2000 x 8

I need to modify the cells of the array so that each cell will contain the sum of all cells above and left of it, inclusive the current cell.

I am doing it using loops like below, but it is taking around 5 minutes to complete the program run. Is there a faster way in Python to achieve this (preferably without a loop)?

for depth in range(simg.shape[2]):
    for row in range(1,simg.shape[0]-1):
        for col in range(1,simg.shape[1]-1):
            simg[row,col,depth]=simg[row-1,col,depth]+simg[row,col-1,depth]+simg[row,col,depth]-simg[row-1,col-1,depth]

Answer 1

I used integral function from openCV. It worked fast (within a second)!

iimg=cv.integral(simg)