title: How to reduce the noise of impulse in image?
body: <p>I want to remove the impulse noise in an image.
  As I know the noise reduction methods is average.
  but I think it doesn't make sense when I use the average method to reduce the noise in image. because, the the average methods don't know this noise is whether impulse noise or not.
  So I want to know how to remove the impulse noise in an image?</p>
  
  <p>would you give any hint?</p>