Issue with python code, why does variable getting overridden?

Question

I have a RGB image of size (227,227,3) and one grayscale image of size (227,227). Now I want to replace RGB planes of the image by the grayscale image. Below I have the code. Now, the issue with code is imgNew is getting overridden even though I am not changing it's value and getting wrong images for imgR,imgG,imgB.

#this is my rgb image 
imgNew = imresize(img[480 / 2 - 160 + r[l, 0]:480 / 2 + 160  + r[l, 0], 640 / 2 - 160 + r[m, 1]:640 / 2 + 160  + r[m, 1], :],(227,227))
# this is grascale 
imgDNew = imresize(imgx[480 / 2 - 160 + r[l, 0]:480 / 2 + 160  + r[l, 0], 640 / 2 - 160 + r[m, 1]:640 / 2 + 160  + r[m, 1]],(227,227))
# if I plot the images here both are fine. 
# Now replacing the planes one by one. 
imgR[:,:,0] = imgDNew
imgR[:,:,1] = imgNew[:,:,1]
imgR[:,:,2] = imgNew[:,:,2]

imgG[:,:,1] = imgDNew
imgG[:,:,2] = imgNew[:,:,2]
imgG[:,:,0] = imgNew[:,:,0]

imgB = imgNew
imgB[:,:,2] = imgDNew
imgB[:,:,0] = imgNew[:,:,0]
imgB[:,:,1] = imgNew[:,:,1]

 #Now if I plot the images my original image is changed (imgNew) and imgR,imgG,imgB images are wrong.

I don't understand what's wrong?

http://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list — Stephen Rauch, May 01 '17 at 01:07

score 4 · Accepted Answer · answered May 01 '17 at 01:07

4

You have this statement: imgB = imgNew which essentially makes imgB to be the same image as imgNew. So when you manipulate imgB in following lines it also changes imgNew. If you wanted imgB to be a copy of imgNew you have to explicitly use a copy function.

answered May 01 '17 at 01:07

petyanca

126
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2

what's that copy function? – talos1904 May 01 '17 at 01:09
`imgNew.copy()` – juanpa.arrivillaga May 01 '17 at 01:10
The following link explains the issue you are having. http://stackoverflow.com/a/5234279/947212 – FrankZappa May 01 '17 at 01:16

Issue with python code, why does variable getting overridden?

1 Answers1