title: PHP fastest way to apply strong blur
body: <p>I need to write a script to blur an image. That wouldn't be a problem if I didn't need it to blur it <strong>really hard</strong>.</p>
  
  <p>Now, GD's gaussian blur filter is really weak. And <a href="http://php.net/manual/en/function.imageconvolution.php" rel="noreferrer">imageconvolution</a> accepts only 3x3 matrixes for some reason so I can't generate <a href="http://en.wikipedia.org/wiki/Gaussian_blur#Sample_Gaussian_matrix" rel="noreferrer">gaussian matrix</a> with larger radius for stronger blur? Even if I could, I'm not sure how fast it would be.</p>
  
  <p>Running gaussian blur multiple times does the trick, but is <strong>really</strong> slow. To achieve effect I'm searching for, I need to run it 40-100 times over an image, and, ofcourse, it takes 10-20 seconds to finish.</p>
  
  <p>Is there a way to achieve what I'm looking for in reasonable time using libraries that come bundled with PHP?</p>
  
  <p>Here is the exact effect. <strong>Generation time: 10.972307920456 seconds. 80 passes.</strong></p>
  
  <h1>Original:</h1>
  
  <p><img src="https://i.stack.imgur.com/KxJZd.jpg" alt="enter image description here"></p>
  
  <h1>Processed:</h1>
  
  <p><img src="https://i.stack.imgur.com/ILeQp.jpg" alt="enter image description here"></p>