1. A method of measuring a visual quality of a processed image, comprising: receiving a first image and a second image, wherein the second image is a processed version of the first image; for each block in the first image, determining a mean square error between the block in the first image and a block in the second image corresponding to the block in the first image; determining a first set of variances of pixel values in a pixel domain or transform coefficients in a transform domain for each block in the first image; determining a second set of variances of pixel values or transform coefficients for each block in the second image; and computing a measure of the visual quality of the second image based at least in part on the measures of discrepancy, the first set of variances and the second set of variances.