title: How do you handle negative pixel values after filtering?
body: <p>I have a 8-bit image and I want to filter it with a matrix for edge detection.  My kernel matrix is </p>
  
  <pre><code>0  1  0
  1 -4  1
  0  1  0
  </code></pre>
  
  <p>For some indices it gives me a negative value. What am I supposed to with them?</p>