Sub-window Box Filter

Box filter is a fundamental filter in image processing. However, it can not preserve edges or corners. In this paper, we present a simple but novel method that can make box filter both edge and corner preserving. More specifically, we combine the box filter with sub-window regression to achieve this task. This filter inherits some properties from box filter, such as O(1) running time with respect to the window radius. After analyzing its parameters, we show its corner and edge preserving property on real images and compare it with Guided filter.