Color interpolation algorithm for an RWB color filter array including double-exposed white channel

In this paper, we propose a color interpolation algorithm for a red-white-blue (RWB) color filter array (CFA) that uses a double exposed white channel instead of a single exposed green (G) channel. The double-exposed RWB CFA pattern, which captures two white channels at different exposure times simultaneously, improves the sensitivity and provides a solution for the rapid saturation problem of W channel although spatial resolution is degraded due to the lack of a suitable color interpolation algorithm. The proposed algorithm is designed and optimized for the double-exposed RWB CFA pattern. Two white channels are interpolated by using directional color difference information. The red and blue channels are interpolated by applying a guided filter that uses the interpolated white channel as a guided value. The proposed method resolves spatial resolution degradation, particularly in the horizontal direction, which is a challenging problem in the double-exposed RWB CFA pattern. Experimental results demonstrate that the proposed algorithm outperforms other color interpolation methods in terms of both objective and subjective criteria.