Demosaicing With Directional Filtering and a posteriori Decision

Most digital cameras use a color filter array to capture the colors of the scene. Downsampled versions of the red, green, and blue components are acquired, and an interpolation of the three colors is necessary to reconstruct a full representation of the image. This color interpolation is known as demosaicing. The most effective demosaicing techniques proposed in the literature are based on directional filtering and a posteriori decision. In this paper, we present a novel approach to this reconstruction method. A refining step is included to further improve the resulting reconstructed image. The proposed approach requires a limited computational cost and gives good performance even when compared to more demanding techniques

I. Introduction

In a typical digital camera, the colors of the scene are captured by a single CCD or CMOS sensor array, where for each pixel the sensor detects a particular color channel, for example red, green or blue. This kind of sensor is called Color Filter Array(CFA). The most popular CFA pattern was introduced by Bayer in [1], and it samples the green band using a quincunx grid, while red and blue are obtained by a rectangular grid, as shown in Fig. 1. In this way, the density of the green samples is twice than that of the red and blue channels. Due to the subsampling of the color components, an interpolation step is required in order to reconstruct a full color representation of the image. This process is called demosaicing, and avoiding the introduction of visible artifacts, such as aliasing and zippering, is desirable.