Geometric Warping Error Aware CNN for DIBR Oriented View Synthesis

Depth Image based Rendering (DIBR) oriented view synthesis is an important virtual view generation technique. It warps the reference view images to the target viewpoint based on their depth maps, without requiring many available viewpoints. However, in the 3D warping process, pixels are warped to fractional pixel locations and then rounded (or interpolated) to integer pixels, resulting in geometric warping error and reducing the image quality. This resembles, to some extent, the image super-resolution problem, but with unfixed fractional pixel locations. To address this problem, we propose a geometric warping error aware CNN (GWEA) framework to enhance the DIBR oriented view synthesis. First, a deformable convolution based geometric warping error aware alignment (GWEA-DCA) module is developed, by taking advantage of the geometric warping error preserved in the DIBR module. The offset learned in the deformable convolution can account for the geometric warping error to facilitate the mapping from the fractional pixels to integer pixels. Moreover, in view that the pixels in the warped images are of different qualities due to the different strengths of warping errors, an attention enhanced view blending (GWEA-AttVB) module is further developed to adaptively fuse the pixels from different warped images. Finally, a partial convolution based hole filling and refinement module fills the remaining holes and improves the quality of the overall image. Experiments show that our model can synthesize higher-quality images than the existing methods, and ablation study is also conducted, validating the effectiveness of each proposed module.