title: Extract heatmap on top of image
body: <p>I have an image like this one
  <a href="https://i.stack.imgur.com/luEBL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/luEBL.png" alt="Heatmap with original image as background"></a>
  and the corresponding background image.
  <a href="https://i.stack.imgur.com/kRB0l.png" rel="noreferrer"><img src="https://i.stack.imgur.com/kRB0l.png" alt="Original image"></a></p>
  
  <p>I am trying to extract the heatmap of the first image. My first approach was to mask every pixel that was not "equal enough" (thresholding the euclidean distance between every pixel), but the results were not good enough
  <a href="https://i.stack.imgur.com/rxSNT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/rxSNT.png" alt="Mask"></a></p>
  
  <p>Looks like a straightforward problem in image processing, but I lack experience. Thanks!</p>