5e0215abab
Implement the dual-filter kawase blur algorithm for the new OpenGL backend as seen in kwin [1]. Use with `--blur-method dual_kawase` and set the desired strength with `--blur-strength level` (1-20). The dual-filter kawase algorithm produces results close to a traditional gaussian blur with higher performace, especially at high blur radii. The supported strength levels provide an effect similar to gauss-radii between 4 and 500 pixels. As this algorithm relies heavily on the texture-filtering units of a GPU, there is no support for the xrender backend — at least for now. [1](https://kwin.kde.narkive.com/aSqRYYw7/d9848-updated-the-blur-method-to-use-the-more-efficient-dual-kawase-blur-algorithm)