The Research And Hardware Realization Of Color Interpolation Algorithm Based On Bayer Color Filter Array

Currently, most digital camera has a CCD or a CMOS sensor which surface iscovered with a color filter array (CFA) to capture color image. Each pixel in the rawimage has captured only one of the three primary colors with the other two missing.This kind of images is called mosaic image. Bayer CFA is the most popular CFA. Inorder to recover the full color image, the other two missing primary color must begenerated by color interpolation algorithm. Although the advanced algorithms willgive better result, but the hardware realization of these algorithms is difficult for realtime. Contrarily, simple algorithm is easier to be realized in hardware but has aunsatisfied result. Therefore, the color interpolation algorithm must take acompromise between the interpolation result and the hardware difficulty in real timeimplementation.In order to achieve the best result of color interpolation by FPGA in real time,this paper analyzes all of the color interpolation algorithms, summarizes the factorswhich determine the effects of the interpolation algorithms, and proposes our colorinterpolation algorithms. In our algorithm, the pixel gradients of the interpolatedimage are calculated, then the image is divided into three kinds of area (The similarsmooth area, Horizon and vertical area, Oblique area). Different area has its own morespecial interpolation strategy; with Matlab tools, the24full color images of Kodak’simage library was processed by the proposed color interpolation algorithm, ADalgorithm and Lu algorithm respectively; then, the statistics of MSE and averagedistance in CIELAB space between raw image and interpolated image were generated;finally, the proposed algorithm was implemented by a Verilog HDL module withpipeline structure; with other necessary modules, the complete verilog system of thispaper’s algorithm was burn into FPGA, and its real-time output images weredisplayed on LCD screen.The Matlab’s simulation and real-time hardware test results show that theproposed color interpolation algorithm is better than AD algorithm and is as good asLu algorithm. It has a pretty good result, especially in the fence area of the lighthouse image. The FPGA hardware realization proved the feasibility and real-time advantageof the proposed algorithm which also avoids division computation in Lu algorithm.The proposed algorithm has a good compromise between interpolation result and thehardware requirement of the real time processing. All of the above indicates that thispaper has achieved its goal.