Ok my first TuT on NB
1. Start a New "Project"
2. insert your image
3. New Layer
4. Choose the rectangle-tool
5. make a big rectangle in white
6. change the angle of the rectangle with CTRL+T
7. rasterize the layer with the rectangle
8. Blurfilter - Blur - Gaußscher Blur and choose what you want, I choose 5.5
9. Set mode on "Overlay"
10. Window - Animation
11. Move the rectangle over the entire image with new frames