Motion Map Generation for Maintaining the Temporal Coherence of Brush Strokes

Abstract

Painterly animation is a method that expresses images with a hand-painted appearance from a video, and the most crucial element for it is the coherence between frames. A motion map generation is proposed in this paper as a resolution to the issue of maintaining the coherence in the brush strokes between the frames. A motion map refers to the range of motion calculated by their magnitudes and directions between the frames with the edge of the previous frame as a point of reference. The different methods of motion estimation used in this paper include the optical flow method and the block-based method, and the method that yielded the biggest PSNR using the motion information (the directions and magnitudes) acquired by various methods of motion estimation has been chosen as the final motion information to form a motion map. The created motion map determined the part of the frame that should be re-painted. In order to maintain the temporal coherence, the motion information was applied to only the strong edges that determine the directions of the brush strokes. Also, this paper sought to reduce the flickering phenomenon between the frames by using the multiple exposure method and the difference map created by the difference between images of the source and the canvas. Maintenance of the coherence in the direction of the brush strokes was also attempted by a local gradient interpolation in an attempt to maintain the structural coherence.