logical indexing 3d array with 2d array

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);

Answer 1

[Stephen23]

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.

[James Tursa]

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);