title: Blur part of an image
body: <p>I want to blur part of a image. I could blur the full image blurred using CIFilter ("CIGaussianBlur") but not a part of it. </p>
  
  <p>For example: I want to blur the image in a small circular or square shape wherever the user taps the image.</p>
  
  <p>How can I do that?</p>