TypeError: 'int' object is not iterable

[tombenj]

Getting this error on some images:

Traceback (most recent call last):
  File "C:\Users\hello\Desktop\Pyxeled\pyxeled.py", line 384, in <module>
    in_rgb = [[list(image_data[r, c]) for c in range(h_in)] for r in range(w_in)]
  File "C:\Users\hello\Desktop\Pyxeled\pyxeled.py", line 384, in <listcomp>
    in_rgb = [[list(image_data[r, c]) for c in range(h_in)] for r in range(w_in)]
  File "C:\Users\hello\Desktop\Pyxeled\pyxeled.py", line 384, in <listcomp>
    in_rgb = [[list(image_data[r, c]) for c in range(h_in)] for r in range(w_in)]
TypeError: 'int' object is not iterable

Any thought as to the cause?