Edge-adaptive color interpolation for complementary color filter array

Abstract

ABSTRACT:Complementary color filter array (CCFA) is widely used in consumer-level digital video cameras, since it not only has high sensitivity and good signal-to-noise ratio in low-light condition but also is compatible with the interlaced scanning used in broadcast systems. However, the full-color images obtained from CCFA suffer from the color artifacts such as false color and zipper effects. These artifacts can be removed with edge-adaptive color interpolation (ECI) approaches which are generally used in primary color filter array (PCFA). Unfortunately, the unique array pattern of CCFA makes it difficult that CCFA adopts ECI approaches. Therefore, to apply ECI approaches suitable for CCFA to color interpolation is one of the major issues to reconstruct the full-color images. In this paper, we propose a new ECI algorithm for CCFA. To estimate an edge direction precisely and enhance the quality of the reconstructed image, a function of spatial variances is used as a weight, and new color conversion matrices are presented for considering various edge directions. Experimental results indicate that the proposed algorithm outperforms the conventional method with respect to both objective and subjective criteria.

Colour demosaicking for complementary colour filter array using spectral and spatial correlations

“…that in [8]), especially in textured regions. In contrast with the method in [9], the proposed method estimates two missing signals at each pixel and therefore not only the luminance image but also two chrominance images can be restored in full-resolution. Moreover, the proposed post-processing step can effectively suppress colour artefacts, meanwhile preserve sharpness.…”

“…After Y, (R 2 Y ) and 2(B 2 Y ) are obtained, a vector-valued colour in the RGB colour space can be restored from these values by using inverse process of the following linear conversion [9] …”

“…1b, each pixel is covered with one of four kinds of colour filters, cyan (hereinafter referred to as Cy), yellow (Ye), magenta (Mg) and green (G). This CCFA is used along with a field integration operation, where an interlaced signal that obtained by adding two vertically adjacent pixels is formed as an output [9,10]. As shown in Fig.…”

“…In the conventional algorithm [8,9], adjacent signals in a line were processed to form the luminance signal (Y ) and chrominance signals (colour difference). For line o 1 in Fig.…”

“…Since the interpolated pixel has a phase difference of about 1/2 pixel from the original image, it cannot work well in regions with fine details. Han et al [9] proposed an edgeadaptive colour interpolation which estimates edge directions and performs interpolation along the edges. The disadvantages of their method are two-fold.…”