Guided Filter in FFmpeg

Dehaze, derain, and denoise are very common image processing tasks, aiming to improve the visual quality of images. Even worse, the low-quality images will seriously influence the accuracy of many computer vision systems. There are many methods for these tasks. The guided filter is a widely known tool that shows remarkable performance for image dehazing and edge-preserving filtering. However, this tool is not supported in FFmpeg. We propose to implement the guided filter in FFmpeg, including the conventional guided filter, fast guided filter and the high-performance guided filter, such as the side-window-based guided filter and so on.