Convert double for loop into recursion func - arrays

Question

I work with two 3D arrays, which the second arr changes according to the first arr.
I try to turn double for loop into a recursive function, but the same error is repeated, RecursionErroe: maximum recursion depth exceeded in comparison.
The for loops i'm trying to convert:
def to_rec(arr):
new = arr.copy()
row_max = len(arr)
col_max = len(arr[0])
for i in range(row_max):
for j in range(col_max):
new[i, j, :] = 255- arr[i, j, :]
return new
RECURSIVE
def rec2(img, row_max, col_max, i, j, new):
if j == col_mac:
return new
else:
new[i, j, :] = 255 - img[i, j, :]
return rec2(img, row_max, col_max, i, j+1, new)
****************************************************
def rec1(img, row_max, col_max, i, j, new):
if i == row_max:
return new
else:
rec2(img, row_max, col_max, i, j, new)
return rec1(img, row_max, col_max, i+1, 0, new)
********************************************************
def to_rec(arr):
......
# The same data as in to_rac func with the for loop
......
new = rec1(arr, row_max, col_max, 0, 0, new)
return new
I can't figure out what is wrong

Answer 1

While this doesn't answer your question about recursion depth, I think the solution is quite simple. It seems you want to invert an image (new[i, j, 0] = 255- arr[i, j, 0]) by looping over all pixels in the image, and then manipulating the pixel value. This can be done highly efficiently using NumPy:
import numpy as np
img = load_img_data() # Replace this by your own data
new_img = 255 - np.array(img)
When your data is stored in a NumPy array, you can trivially perform scalar arithmetics (addition, multiplication, etc.) on matrices. This way you don't have to perform nested loops (or recursive operations).

Answer 2

The search term RecursionError: maximum recursion depth exceeded has plenty of answers on SO - the reason is simple:
you try to recuse but your function/data does not allow it:
data too big so that you would need to recurse max_depth+n times to solve it
your data (or method) will never reach the end-condition of your recursion
your function has no end condition
Your recursion is flawed and you never reach the end - hence you dive deeper and deeper and put callstack upon callstack until python raises the error to avoid a Stackoverflow from accumulated stack frames due to thousands of function calls.
Ex:
# recurses crashes every time (no end condition)
def no_end_1(k = True):
no_end_1(not k)
# recursion works if you call it with some data but not with other data
def no_end_2(i):
if i == 0:
return "Done"
no_end_2(i-1)
no_end(25) # works
no_end(-3) # crashes
def flawed_collatz_testmethod(a):
# collatz conjectur holds for numbers up to
# 2.361.183.346.958.000.000.001 (wikipedia), they converge on 1
if a%2 == 0:
new_a = a//2
else:
new_a = 3*a+1
if new_a < 1:
print ("Collatz was wrong")
else:
# will eventually end in a loop of 4-2-1-4-2-1-4-2-1-... and crash
flawed_method(new_a)
In any case .. you need to fix your function. Best way to do it is to take a small datasample, a pen and paper and draw/calculate what the function does to see why it recurses endlessly.