Proceedings Article | 17 January 2006
KEYWORDS: Image quality, Quality measurement, JPEG2000, Discrete wavelet transforms, Image compression, Molybdenum, Interference (communication), RGB color model, Video, Image processing
Image quality assessment plays a major role in many image processing applications. Although much effort has been made in recent years towards the development of quantitative measures, the relevant literature does not include many papers that have produced accomplished results. Ideally, a useful measure should be easy to compute, independent of viewing distance, and able to quantify all types of image distortions. In this paper, we will compare three full-reference full-color image quality measures (M-DFT, M-DWT, and M-DCT). Assume the size of a given image is nxn. The transform (DFT, DWT, or DCT) is applied to the luminance layer of the original and degraded images. The transform coefficients are then divided into four bands, and the following operations are performed for each band: (a) obtain the magnitudes Moi, i=1,..., (nxn/4) of original transform coefficients, (b) obtain the magnitudes Mdi, i=1,..., (nxn/4) of degraded transform coefficients, (c) compute the absolute value of the differences: |Moi-Mdi|, i=1,..., (nxn/4), and (d) compute the standard deviation of the differences. Finally, the mean of the four standard deviations is obtained to produce a single value representing the overall quality of the degraded image. In our experiments, we have used five degradation types, and five degradation levels. The three proposed full-reference measures outperform the Peak-Signal-to-Noise Ratio (PSNR), and two state-of-the-art metrics Q and MSSIM.
