Color interpolation by expanding a gradient method

Abstract

This paper proposes a color filter array interpolation method, which expands the preceding gradient based scheme by adopting Gaussian low-pass filter. It starts from the assumption that high frequency components of the green plane in an image are almost the same as those of the red or blue planes in the same image. We identify that the conventional gradient method can make use of this idea and can be expanded by Gaussian low-pass filter to enhance its performance. To determine the reasonable mask size and the appropriate Gaussian sigma value, various values are tested with sample images, and used later to interpolate the green plane for other test images in the proposed method. Afterward, red and blue plane interpolations are performed, and directional median processing is applied along the flat edge lines. This process can effectively suppress false colors introduced during the interpolation of color planes. The proposed method provides a reasonable visual quality and generally higher peak-signal-to-noise-ratio compared to existing methods.