title: Questions about edge detection in an image
body: <p>I think for those images with many edges, it would be more useful to use color images because this will give greater image gradient, so shaper edeges is detected. However, I have no ideas about the second questions. Does it mean we can add linear transformations or some constant value to the image?</p>
  
  <p><a href="https://i.stack.imgur.com/FCgj4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FCgj4.png" alt="enter image description here"></a></p>