This paper demonstrates how the nonlocal principle benefits video matting via the KNN Laplacian, which comes with a straightforward implementation using motion-aware K nearest neighbors. In hindsight, the fundamental problem to solve in video matting is to produce spatio-temporally coherent clusters of moving foreground pixels. When used as described, the motion-aware KNN Laplacian is effective in addressing this fundamental problem, as demonstrated by sparse user markups typically on only one frame in a variety of challenging examples featuring ambiguous foreground and background colors, changing topologies with disocclusion, significant illumination changes, fast motion, and motion blur. When working with existing Laplacian-based systems, we expect our Laplacian can benefit them immediately with an improved clustering of moving foreground pixels.

   @inproceedings{knn_video_matting_iccv2013,
     author={Dingzeyu Li and Qifeng Chen and Chi-Keung Tang}, 
     booktitle={International Conference on Computer Vision (ICCV), 2013}, 
     title={Motion-Aware KNN Laplacian for Video Matting}, 
     year={2013}, 
   }