NDLI: An Efficient Compression Scheme for Colour Filter Array Images Using Estimated Colour Differences

Content Provider	IEEE Xplore Digital Library
Author	Doutre, C. Nasiopoulos, P.
Copyright Year	2007
Description	Author affiliation: Univ. of British Columbia, Vancouver (Doutre, C.; Nasiopoulos, P.)
Abstract	Most consumer digital cameras capture colour images using a single light sensor and a colour filter array (CFA). The CFA allows only one colour of light (red, green, or blue) to reach the sensor at each pixel location. This results in a mosaic image being captured, where either a red, green or blue sample is captured at each location. The two missing colours must be interpolated from the surrounding samples in a process called demosaicking. The conventional approach to performing compression in these cameras is to first perform demosaicking and then compress the resulting full colour image with standard methods. However, recent work has attempted to compress the raw data captured by the sensor, with demosaicking being performed later. One challenge with this method (compression before demosaicking) is exploiting the correlation between the red, green and blue colour planes. Existing methods have used a modified YCbCr colour space conversion which is applied to groups of RGB samples captured at adjacent pixel locations. This results in poor performance around edges, where there is much lower correlation between the RGB samples. In this paper, we propose a new method of exploiting correlation between RGB samples when compressing CFA images. We use a 2D 5times5 linear filter to estimate the green value at each location where a red or blue sample is captured. We then compress the captured green samples, and two "chrominance" planes, which are obtained by taking the difference between the captured red and blue samples and the estimated green value at the same location. This results in much smoother chrominance signals than the modified YCbCr conversion used in previous work. Simulation results show that for different images, the proposed method results in bit rate reductions between 12-25% relative to the previous modified YCbCr conversion when compressing CFA images with JPEG.
Starting Page	24
Ending Page	27
File Size	396658
Page Count	4
File Format	PDF
ISBN	1424410207
ISSN	08407789
DOI	10.1109/CCECE.2007.13
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2007-04-22
Publisher Place	Canada
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Image coding Nonlinear filters Sensor arrays Image converters Digital cameras Image sensors Digital filters Optical arrays Color Bit rate
Content Type	Text
Resource Type	Article
Subject	Electrical and Electronic Engineering Hardware and Architecture

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