The image sensors capture image signals in a color filter array (CFA) format. After demosaicking and RGB-to-YUV conversion, YUV 420 subsampling is performed for image/video compression. In recent work, YUV 420 subsampling is considered in either of two schemes: subsampling the chrominance while keeping the luminance values the same, or finding optimal luminance values given subsampled chrominance values. In this paper, we extended prior work by reducing the search space to a few Y candidates by observing multiple intervals in the pixel distortion curve, and by developing more flexible, structured cost functions to enable further optimization of the recovered pixels. The closed-form solution still requires a parameter set for each pixel location. Therefore, several methods for reducing complexity are proposed. In comparison to previous methods evaluated on two benchmark datasets, IMAX and SCI, our approach consistently improves image quality (measured in dB) while incurring only minimal increases in computation time (in seconds). Specifically, for the SCI dataset, relative to the Unoptimized Luminance method, we achieve an average CPSNR increase of 3.69 to 7.15 dB, accompanied by an increase in computation time of 12.35 to 13.63 s. In contrast, the Optimized Luminance method yields an average CPSNR improvement of 2.84 to 5.67 dB, with a lower computation time of 0.24 to 3.94 s. For the IMAX dataset, when compared to the unoptimized Luminance method, we note an average CPSNR enhancement of 1.66 to 4.58 dB, with a corresponding rise in computation time of 7.00 to 8.71 s. Meanwhile, the Optimized Luminance method results in an average CPSNR increase of 0.4 to 3.73 dB, with a modest computation time increase of 2.07 to 2.86 s.
扫码关注我们
求助内容:
应助结果提醒方式:
