title: How to remove gaussian noise from an image in MATLAB?
body: <p>I'm trying to remove a Gaussian noise from an image. I've added the noise myself using:</p>
  
  <pre><code>nImg = imnoise(img,'gaussian',0,0.01);
  </code></pre>
  
  <p>I now need to remove the noise using my own filter, or at least reduce it. In theory, as I understand, using a convolution matrix of <code>ones(3)/9</code> should help and using a Gaussian convolution matrix like <code>[1 2 1; 2 4 2; 1 2 1]/9</code> or <code>fspecial('gaussian',3)</code> should be better. Yet, they really don't do the trick so well:
  <img src="https://i.stack.imgur.com/00c24.jpg" alt="enter image description here"></p>
  
  <p>Am I missing something important? I need to use convolution, by the way.</p>