Fast realistic block-based refocusing for sparse light fields

View-interpolation-based refocusing achieves realistic quality for sparse light fields but requires lots of computation. In this paper, we aim to reduce the computation load while maintaining the superior refocusing quality. The idea is to interpolate only few views for infocused regions and to perform refocusing on downsampled pixels for defocused area. This is achieved b y a proposed block-based refocusing algorithm which consists of multi-level refocusing mode decision and timing-based bloc k merging. For each variable-size block, the former chooses the fastest downsampling mode given that the distortion is negligible based on a localized filter response analysis. Then, the latter determines the fastest quadtree block partition by minimizing the timing cost which is accurately estimated for each block. Experimental results show that a 10x speedup on average is achieved for realistic refocusing. Also, the computation time becomes comparable to the conventional fast depth-dependent blurring which has serious boundary artifacts.