Application of the CIE color spaces for the digital image quality assessment

The digital image quality assessment is one of the most relevant aspects of contemporary digital image processing. A rapid development of some modern quality assessment techniques in recent years has caused the introduction of some new metrics, much better correlated with the Human Visual System (HVS) than the traditional ones such as the Mean Squared Error (MSE) or PSNR (Peak Signal to Noise Ratio). One of the most popular modern image quality assessment techniques is the usage of the Structural Similarity index (SSIM) defined in 2004. Unfortunately, even some modern image quality metrics are usually defined for the grayscale images so the colour information is often ignored. A typical classical approach to the quality assessment of the color images is the use of the Normalized Color Difference calculated in the CIE L*a*b* ob CIE Lu'v' colour space but its correlation with the human assessment is rather poor. In the paper the analysis of the influence of using the color spaces recommended by the CIE on the results of the digital image quality assessment using some modern metrics is performed. All the results have been calculated for the widely known LIVE database (release 2) containing the Differential Mean Opinion Scores (DMOS) for nearly 1000 color images with five types of distortions: JPEG compression, JPEG2000 compression, Gaussian blur, white noise and transmission over the simulated fast fading Rayleigh channel typical of wireless transmissions. As the final result the comparison of the correlations between the DMOS values and the SSIM metric calculated for various colour spaces recommended by the CIE is presented.