Although image contrast enhancement is a low level image processing issue, it is very important for improving image quality. This paper propose a new algorithm using optimal linear transform to enhance color image while preserving hue attributes and scaling saturation for each color pixel. The algorithm has two features: 1) optimal piecewise affine transform is used for equalizing intensity histogram and the partition of accumulative histogram is optimized using a line regression; 2) the

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... hm solves out-of-gamut problem since saturation of each pixel is constrained by scaling inside the boundary of LCC color space in each hue direction. Many experiments have been conducted and the results show that the proposed algorithm enhances color image contrast well while preserving hues better.