title: Image "gradient blur"
body: <p>in my application, I need to apply a blur-filter to an image. However, the effect should get stronger, the further the pixel is away from a line the user may draw freely in the image.</p>
  
  <p>Lets assume the line the user draws splits the image horizontally exactly in the middle. Then along this line, the effect of the gradient should be 0%, half the way up and down from this line, the effect should be 50% etc. (If you have Picasa on your machine, there's a similar effect for an elliptic gradient)</p>
  
  <p>Now I thought I might try the following (which I have not, so far - I'm just collecting ideas here): I might create a 100% blurred version of the image and combine it with the original image using an alpha-mask. This alpha-mask would be created from a simple black/white linear gradient.</p>
  
  <p>Do you think this might work? Are there other implementations possible using filters directly?</p>