title: Approximating Gaussian Blur Using Extended Box Blur
body: <p>The problem is a s following, how to approximate a Gaussian Blur Filter with a given STD using Box Blur / Extended Box Blur.  </p>
  
  <p>More specifically, I know this is the way Photoshop applies its Gaussian Blur.</p>
  
  <p>First, an article about "Extended Box Blur can be seen here - <a href="http://www.mia.uni-saarland.de/Publications/gwosdek-ssvm11.pdf" rel="nofollow">Theoretical Foundations of Gaussian Convolution by Extended Box Filtering</a>.</p>
  
  <p>The problem I'm having is with Figure 2 in the article.<br>
  The best way to explain this would be using an example.  </p>
  
  <p>Let's say we need to approximate a Gaussian Blur with STD of 15.4 -> Var = 237.16.<br>
  In order to have a good approximation we'll do that with 6 iterations of a Box Blur.</p>
  
  <p>Now, How do I choose the length of the Box Blur (We'll do it in a separable manner, namely, working in 1D)?<br>
  Should I chose different lengths (It seems I have to)?<br>
  The target is matching the GB Level of Blur (Which is its STD / VAR).</p>
  
  <p>Thank You.</p>
  
  <p>P.S.<br>
  I'm working on MATLAB, so code is easy :-).</p>