Tried to split image and kept getting error message

Python
1

i was trying to split an image into red channel,blue channel and green channel, using cv2.split() function. i keep getting an error message. that says Traceback (most recent call last):
File “C:\Users\david\AppData\Local\Programs\Python\Python36-32\p99.py”, line 5, in
(R,G,B) = cv2.split(q);
ValueError: not enough values to unpack (expected 3, got 0)

how do i eliminate this error message.
i tried reinstalling opencv. i tried reinstalling idle. i tried system restore.

2

your input (q) is invalid, try to find out why

>>> q = None
>>> cv2.split(q)
[]
>>> (r,g,b) = cv2.split(q)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not enough values to unpack (expected 3, got 0)
3

I forgot to write my code. I was under a lot of stress. My code is

import cv2

q = cv2.imread(‘mm.PNG’);
w = cv2.split(q);

4

My code is,

import cv2

q = cv2.imread(‘mm.PNG’);
(R,G,B) = cv2.split(q);

5

I zoned out the first time and wrote the code wrong the first. I am sure it is right the second time.

6

Here is my code,

import cv2

q = cv2.imread(‘mm.PNG’);
(R,G,B) = cv2.split(q);

I am sure it is right this time.

7

this is the main failure. your image did not load.
‘mm.PNG’ is not, where your program starts
imread() returns None in that case.
you should add a check like :
if (np.shape(img)==()): #read error, you cant go on !
after each imread(), to be safe !

will return an empty [] then (again, see example above !),
and you cannot unpack that to a rgb tuple
(which would be bgr order in opencv anyway)

8

Thanks for the advice

9

in fact the result is None, so you can also check:

if img is None: # that's bad
    pass # do something about it

or just check and fail:

assert img is not None
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