The Blur mode "Gauss Extended" works well, but there may be situations in which you may want to blur an image while the edges remain sharp. The attached project shows a kind of solution, even if it looks a bit cumbersome. In order to use this method you may start the project, open slide 2, and replace one instance of the included Main object 1 by one of your own images (any aspect ratio); finally you may copy the whole thing to your own projects. You may create a style from slide 2, which has the disadvantage to loose the objects' names.
Blur_with_sharp_edges.zip