title: How does kernel work in unsharp masking?
body: <p>I applied the kernel below to the picture for unsharp masking <img src="https://i.stack.imgur.com/S5DFe.jpg" alt="enter image description here"> </p>
  
  <pre><code>k = [-1 -1 -1; -1 8 -1; -1 -1 -1]
  </code></pre>
  
  <p>I got <img src="https://i.stack.imgur.com/VyEMd.jpg" alt="enter image description here"></p>
  
  <p>Then I changed 8 to 14. And I got <img src="https://i.stack.imgur.com/ujOBR.jpg" alt="enter image description here"></p>
  
  <p>How does kernel work for unsharp masking the original picture and what does exactly do the number in the middle ?</p>