Journal of Broadcast Engineering (방송공학회논문지)

The Korean Institute of Broadcast and Media Engineers (한국방송∙미디어공학회)
권호 표지
DOI QR코드

DOI QR Code

Enhanced Weighted Directional Demosaicking using Edge Indicator

에지 지시자를 이용한 향상된 방향 가중치 디모자이킹 알고리듬

  • 류지만 (한양대학교 전자컴퓨터통신공학과) ;
  • 양시영 (한양대학교 전자통신전파공학과) ;
  • 임태환 (한양대학교 전자컴퓨터통신공학과) ;
  • 정제창 (한양대학교 전자전기컴퓨터공학부 (영상통신 및 신호처리 연구실))
  • Received : 2009.12.14
  • Accepted : 2010.02.03
  • Published : 2010.03.30
Download PDF
⟨ Previous Next ⟩

Abstract

A color image requires at least three color channels to obtain the full color image. However the image sensor obtains only the intensity of the brightness, that is, three image sensors are required for every pixel to capture the full color image. Since the image sensor is quiet expensive, most of digital still cameras adopt single image sensor array with color filter array (CFA) to reduce the size and the cost. Since the image obtained using single sensor array has only one color component per pixel, we need to reconstruct the missing two color components to obtain the full color image. We call this process as color filter interpolation or demosaicking. In this paper, demosaicking algorithm composed of two large step is proposed. Proposed algorithm is combined with several different algorithms such as Edge-directed demosaicking, Second-order gradients as correction terms, Smooth hue transition Interpolation, etc. The simulation results show that the proposed algorithm performs much better than the state-of-the-art demosaicking algorithms in terms of both subjective and objective qualities.

디지털 영상에서 색을 표현하기 위해서는 최소 세 개 이상의 색 채널이 필요하다. 하지만 디지털 카메라에서 영상을 얻기 위해 사용되는 영상 센서는 빛의 밝기 정보만을 받아들일 뿐 색 정보를 분리해낼 수 없으므로 각 화소당 세 개의 영상 센서를 배치 한 뒤 색필터를 사용하여 색 영상을 얻어내게 된다. 대다수의 디지털 카메라는 제품의 크기를 최소화 하고 제조 단가를 절감하기 위하여 단일 영상 센서 배열을 사용한다. 이런 단일 영상 센서를 통해 얻어진 영상들은 각 화소당 하나의 색 정보만을 포함하고 있기 때문에, 사람이 본래의 색으로 영상을 보기 위해서는 각 화소당 나머지 두 개의 손실된 색 정보를 복원해야 하며 이 과정을 색 필터 보간(color filter array interpolation) 혹은 디모자이킹(demosaicking) 과정이라 부른다. 본 논문에서는 두 차례에 걸친 디모자이킹 단계를 통해 여러 가지 기법을 복합적으로 사용함으로써 더 정확한 색을 복원하는 기법을 제안하고 있으며, 에지 기반 보간법, 2차 미분값을 보정값으로 사용하는 기법, 색차를 이용하는 기법, 가중치 합을 이용한 기법 등이 사용되어서 화질을 개선하고 있다. 기존의 기법들과 객관적, 주관적 비교를 수행하여 제안하는 기법이 다른 기법들에 비해 더 좋은 성능을 보여주는 것을 확인하였다.

Keywords

References

  1. K. Jain, Fundamentals of digital image processing, Prentice Hall: New Jersey, 1986.
  2. R. C. Gonzalez, R. E. Woods, Digital Image Processing, Addison Wesley, 1992.
  3. K. N. Plataniotis and A. N. Venetsanopoulos, Color Image Processing and Applications, Springer, 2000.
  4. B. E. Bayer, "Color imaging array," U.S. Patent 3 971 065, July 1976.
  5. K. Hirakawa and P. J. Wolfe, "Spatio-Spectral Color Filter Array Design for Optimal Image Recovery," IEEE Transactions on Image Processing, vol. 17, no. 10, pp. 1876-1890, Oct. 2008. https://doi.org/10.1109/TIP.2008.2002164
  6. Sony Corporation, "Realization of Natural Color Reproduction in Digital Still Cameras, Closer to the Natural Sight Perception of the Human Eye," [Online]. Available: http://www.sony.net/SonyInfo/News/Press_Archive/200307/03-029E/, July 2003.
  7. T. Kijima, H. Nakamura, J. Compton, and J. Hamilton, "Image sensor with improved light sensitivity," U.S. Patent Application 2007 0 177 236, Aug. 2007
  8. D. R. Cok, "Signal processing method and apparatus for producing interpolated chrominance values in a sampled color image signal," U.S. Patent 4 642 678, Feb. 1987
  9. S.-C. Pei and I.-K. Tam, "Effective color interpolation in CCD color filter arrays using signal correlation," IEEE Transactions on Circuits and Systems for Video Technology, vol.13, no. 6, pp. 503-513, Jun. 2003. https://doi.org/10.1109/TCSVT.2003.813422
  10. R. H. Hibbard, "Apparatus and method for adaptively interpolating a full color image utilizing luminance gradients," U.S. Patent 5 382 976, Jan. 1995.
  11. C. A. Laroche and M. A. Prescott, "Apparatus and method for adaptively interpolating a full color image utilizing chrominance gradients," U.S. Patent 5 373 322, Dec. 1994.
  12. W. Lu and Y. P. Tan, "Color filter array demosaicking: New method and performance measures," IEEE Transactions on Image Processing, col. 12, no. 10, pp. 1194-1210, Oct. 2003. https://doi.org/10.1109/TIP.2003.816004
  13. R. Kimmel, "Demosaicing: Image reconstruction from color CCD samples," IEEE Transactions on Image Processing, vol. 8, no. 9, pp. 1221-1228, Sep. 1999. https://doi.org/10.1109/83.784434
  14. J. E. Adams and J. F. Hamilton, "Adaptive color plane interpolation in single color electronic camera," U.S. Patent 5 506 619, April 1996.
  15. J. F. Hamilton and J. E. Adams, "Adaptive color plane interpolation in single sensor color electronic camera," U.S. Patent 5 629 734, May 1997.
  16. Hung-An Chang and Homer Chen, "Directionally weighted color interpolation for digital cameras," in proc. IEEE International Symposium on Circuits and Systems, vol. 6, pp. 6284-6287 23-26 May 2005.
  17. B. K. Gunturk, Y. Altunbasak, and R. M. Mersereau, "Color plane interpolation using alternating projections," IEEE Transactions on Image Processing, vol.11, no.9, pp. 997-1013, Sep. 2002. https://doi.org/10.1109/TIP.2002.801121
  18. X. Li, "Demosaicing by successive approximation," IEEE Transactions on Image Processing, vol. 14, no.3, pp. 370-379, Mar. 2005. https://doi.org/10.1109/TIP.2004.840683
  19. R. Lukac and K. N. Plataniotis, "Normalized Color-Ratio Modeling for CFA Interpolation," IEEE Transactions on Consumer Electronics, vol. 50, no.2, pp. 737-745, May 2004. https://doi.org/10.1109/TCE.2004.1309456
  20. R. Lukac and K. N. Plataniotis, "Data-Adaptive Filters for Demosaicking: A Framework," IEEE Transactions on Consumer Electronics, vol. 51, no. 2, pp. 560-570, May 2005. https://doi.org/10.1109/TCE.2005.1468002
  21. K. Hirakawa and T. W. Parks, "Adaptive homogeneity-directed demosaicing algorithm," IEEE Transactions on Image Processing, vol. 14, no. 3, pp. 360-369, Mar. 2005. https://doi.org/10.1109/TIP.2004.838691