logical indexing 3d array with 2d array

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RuiQi
RuiQi on 17 Jan 2017
Edited: Stephen23 on 17 Jan 2017
how can i set the values of my matrix to a certain rgb value given a mask ?
image_a; %(640x480x3) uint8
mask; %(640x480x1) logical mat
image_a(mask) = cv::RGB(255,200,0);

Accepted Answer

Stephen23
Stephen23 on 17 Jan 2017
Edited: Stephen23 on 17 Jan 2017
Exactly like I showed you in your earlier identical question (Method 2):
A(mask(:,:,[1,1,1])) = value
If you have a single RGB value that you want to allocate to the masked points then use imoverlay from the image processing toolbox:
B = imoverlay(A,mask,rgb)
If you do not have the image processing toolbox then you can get much the same effect by using bsxfun:
B = bsxfun(@times,A,~mask) + bsxfun(@times,rgb,mask)
where rgb is a single triple of size 1*1*3, and both mask and rgb are of the same class as the image A.
  1 Comment
James Tursa
James Tursa on 17 Jan 2017
OP has three different values he wants to set for the planes. So this is a slightly different question. E.g.,
image_a(mask(:,:,[1,1,1])) = repmat(value(:)',sum(mask(:)),1);

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