OpenCV cv2.add TypeError with arguments

Asked May 12 '21 at 17:26

Active May 12 '21 at 17:42

Viewed 189 times

I am trying to run the code in this answer to make an image brighter.

The code in question is:

import cv2
import numpy as np

# as people point out in comments, cv2.read() from the original
# code no longer works
image = cv2.imread('image.png')   
hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
value = 42 #whatever value you want to add
cv2.add(hsv[:,:,2], value, hsv[:,:,2])
image = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)
cv2.imwrite('out.png', image)

On the line cv2.add(hsv[:,:,2], value, hsv[:,:,2]) I get the following error

TypeError: Expected Ptr<cv::UMat> for argument 'dst'

This happens with any input image I've tried and someone else posted the same issue as a comment to that answer. How can this be fixed?

EDIT: as people have pointed out you won't be able to run cv2.read above. You'll ne

edited May 12 '21 at 17:42

asked May 12 '21 at 17:26

Vainmonde De Courtenay

Try using `cv2.imread` instead of `cv2.read` and be sure to use an absolute path to the image. – stateMachine May 12 '21 at 17:35
Yeah I'm doing that. The problem line is definitely the `cv2.add()`. I've viewed the images, checked the arrays, etc. – Vainmonde De Courtenay May 12 '21 at 17:37
No, you're not, at least not according to the "code in question". In it's present form that will end in error, since there's no such thing as `cv2.read`. – Dan Mašek May 12 '21 at 17:38
1

The problem is `hsv[:,:,2]` as a destination -- that has step size set to skip the other channels, and while OpenCV can use that as an input, it can't use it as an output. – Dan Mašek May 12 '21 at 17:42
Ok I've updated with the change from cv2.read to .imread, which is true ofcourse – Vainmonde De Courtenay May 12 '21 at 17:42
2

I'd just do `cv2.add(hsv, (0,0,value,0), hsv)`. NB it has to be a tuple with 4 values, so it gets recognised as a scalar. – Dan Mašek May 12 '21 at 17:44
@DanMašek working - pls put in an answer so I can accept – Vainmonde De Courtenay May 12 '21 at 18:01

OpenCV cv2.add TypeError with arguments

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