Abstract

Digital refocusing has a tradeoff between complexity and quality when using sparsely sampled light fields for low-storage applications. In this paper, we propose a fast physically-correct refocusing algorithm to address this issue in a two-fold way. First, view interpolation is adopted to provide photorealistic quality at infocus-defocus hybrid boundaries. Regarding its conventional high complexity, we devised a fast line-scan method specifically for refocusing, and its 1D kernel can be 30x faster than the benchmark VSRS-1D-Fast. Second, we propose a block-based multi-rate processing flow for accelerating purely infocused or defocused regions, and a further 3-34x speedup can be achieved for high-resolution images. All candidate blocks of variable sizes can interpolate different numbers of rendered views and perform refocusing in different subsampled layers. To avoid visible aliasing and block artifacts, we determine these parameters and the simulated aperture filter through a localized filter response analysis using defocus blur statistics. The final quadtree block partitions are then optimized in terms of computation time. Extensive experimental results are provided to show superior refocusing quality and fast computation speed. In particular, the run time is comparable to the conventional single-image blurring which causes serious boundary artifacts.

Publication

C.-T. Huang, et. al., "Fast Physically-Correct Refocusing for Sparse Light Fields Using Block-Based Multi-Rate View Interpolation," IEEE Transactions on Image Processing, to appear.
[preprint (20MB)]

Supplementary Results: Block-based refocusing with five views (SSLF-5, u_t = 1.0)

The following videos sweep focal stacks in a front-back-front order, and the image sizes are scaled for viewing.

Camera

Kid and Cat

Girl and Pigeon

Kid and Ball

StillLife

Lego Knights

Acknowledgement

This work was supported by the Ministry of Science and Technology, Taiwan, R.O.C. under Grant No. MOST 103-2218-E-007-008-MY3.

Last update on Nov 19, 2016