Color Image Enhancement with CLAHE based DC Coefficients Scaling in LAB Color Space

The low cost cameras usually capture the low contrast color images which are differ than the brightness of the original scene. This is because of non-uniform scene illumination, blur due to long shutter time of low cost cameras, and may be due to occlusion or shadows. Therefore many contrast enhancement methods for true color image enhancement are designed in past. In this paper a new methodology for image enhancement is proposed by combining the contrast limited adaptive histogram equalization (CLAHE) method with the DC coefficient scaling method. As an additional modification instead of conventional Y-Cb-Cr color space, it is proposed to use LAB color space. The performance of CLAHE method and DC coefficient scaling method are compared with proposed enhancement method in DCT domain for color contrast enhancement. The contrast is enhanced only for L component and preserving the color chrominance information. This improves the contrast and entropy, and reduces the effect of color shifting in standard methods. The absolute standard deviation difference and entropy is used for performance evaluation parameters. The methods are evaluated under different true color imaging environments.