Comparisons of Color Spaces for Shadow Elimination

그림자 제거를 위한 색상 공간의 비교

  • 이광국 (한양대학교 전자컴퓨터통신공학과) ;
  • ;
  • 윤자영 (한양대학교 건축환경공학과) ;
  • 김재준 (한양대학교 건축공학부) ;
  • 김회율 (한양대학교 전자통신컴퓨터공학부)
  • Received : 2008.02.14
  • Accepted : 2008.04.04
  • Published : 2008.05.31

Abstract

Moving object segmentation is an essential technique for various video surveillance applications. The result of moving object segmentation often contains shadow regions caused by the color difference of shadow pixels. Hence, moving object segmentation is usually followed by a shadow elimination process to remove the false detection results. The common assumption adopted in previous works is that, under the illumination variation, the value of chromaticity components are preserved while the value of intensity component is changed. Hence, color transforms which separates luminance component and chromaticity component are usually utilized to remove shadow pixels. In this paper, various color spaces (YCbCr, HSI, normalized rgb, Yxy, Lab, c1c2c3) are examined to find the most appropriate color space for shadow elimination. So far, there have been some research efforts to compare the influence of various color spaces for shadow elimination. However, previous efforts are somewhat insufficient to compare the color distortions under illumination change in diverse color spaces, since they used a specific shadow elimination scheme or different thresholds for different color spaces. In this paper, to relieve the limitations of previous works, (1) the amount of gradients in shadow boundaries drawn to uniform colored regions are examined only for chromaticity components to compare the color distortion under illumination change and (2) the accuracy of background subtraction are analyzed via RoC curves to compare different color spaces without the problem of threshold level selection. Through experiments on real video sequences, YCbCr and normalized rgb color spaces showed good results for shadow elimination among various color spaces used for the experiments.

Acknowledgement

Supported by : 한국건설교통기술평가원