MATLAB: Marking pixels above a certain value

#pixelmarking

Hello. I have a problem.Let's say we have an image called img1 and I want to do the following two things (without loops):
"1. Create logical image where every pixel is marked that has a green channel which is greater or equal 0.5. The result should be stored in mark_green."
"2. Set all pixels in the original image (the double image from step 2) to black where _mark_green is true. Store the result in image_masked. Use repmat to complete this task."
Any ideas?

Best Answer

Hint for the 1st part,
G = (insert code here to pick off the green plane)
mark_green = G >= 0.5; % the marked pixels
For the 2nd part, repmat ~mark_green so that it can be used for all of the color planes. You might want to .* the result with your image.
Give it a try, and then post your code if you have problems and need specific advice.
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