Joint Demosaicing and Subpixel-Based Down-Sampling for Bayer Images: A Fast Frequency-Domain Analysis Approach
A portable device such as a digital camera with a single sensor and Bayer color filter array (CFA) requires demosaicing to reconstruct a full color image. To display a high resolution image on a low resolution LCD screen of the portable device, it must be down-sampled. The two steps, demosaicing and down-sampling, influence each other. On one hand, the color artifacts introduced in demosaicing may be magnified when followed by down-sampling; on the other hand, the detail removed in the down-sampling cannot be recovered in the demosaicing. Therefore, it is very important to consider simultaneous demosaicing and down-sampling. In this paper, we propose a fast frequency-domain analysis approach for joint demosaicing and subpixel-based down-sampling (FFA-JDSD) of single sensor Bayer images. In FFA-JDSD, we integrate demosaicing into down-sampling by directly performing subpixel-based down-sampling in the Bayer domain, due to which the computational complexity is significantly reduced. We use a frequency domain analysis tool to show that the cut-off frequency of the low-pass filter for JDSD can be effectively extended beyond the Nyquist frequency, resulting in much sharper down-sampled images. Experimental results show that, compared with the methods that separately perform demosaicing and down-sampling, FFA-JDSD has much less computational complexity, and can produce much sharper results at the expense of slight color fringing artifact.
down-sampling demosaicking subpixel rendering