how to change pixel values in python (opencv) without for loops

Question

I'm starting with OpenCV in Python and I have a problem.

I have a depth image taken from a kinect camera. This image has a border whose pixel values are zero. I want to change those values to the maximum of the image (that is 2880) without using for loops.

The code until here is:

import cv2
 depthImage = cv2.imread('depthImageName',cv2.IMREAD_UNCHANGED)
 if depthImage.any() == 0:
     depthImage = 2880

But it doesn't work and the values equal to zero remain.

Anyone who can help me?

If I've forgotten useful information, let me know.

Thanks in advance guys! :)

Amin Suzani · Accepted Answer · 2015-02-05 22:28:33Z

1

When you read the image file using imread, it is stored in a numpy array. Therefore, you can use the indexing of numpy arrays. like this:

depthImage[depthImage==0] = 2880

answered Feb 5, 2015 at 22:28

Amin Suzani

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4 Comments

Andrey Over a year ago

Even if it is true it will iterate anyway, while if this is border it can be done in 4 iterations

Amin Suzani Over a year ago

yeah, but it's a highly optimized iteration. In addition, the top,left,bottom,right values might not be known or might be inconsistent for different input images. Or one might not want to change the image size.

Andrey Over a year ago

But OP specified that he wants to replace zeroes in borders only, but his code looks differently.

Amin Suzani Over a year ago

You're right about that, but my answer is exactly what he/she is trying to do in his/her sample code. That's why I assumed changing all zero values wouldn't be a problem.

Andrey · Accepted Answer · 2015-02-05 22:22:21Z

1

There is a function that can create borders, copyMakeBorder, here is python tutorial:

img1 = cv2.imread('opencv_logo.png')
constant= cv2.copyMakeBorder(img1,10,10,10,10,cv2.BORDER_CONSTANT,value=BLUE)

answered Feb 5, 2015 at 22:22

Andrey

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