Localized Distortion Estimation from Already Compressed JPEG2000 Images

We consider the estimation of local residual distortion from an already compressed image, without access to the original. We are motivated by applications in which multiple compressed views of a scene are combined to obtain a single best rendering. However, other applications in image analysis and reconstruction could doubtless benefit from reliable local distortion estimates. We show that prediction of the residual distortion in JPEG2000 code-blocks is tantamount to extrapolating distortion-rate slope information. It also appears that the extrapolation problem can be rendered more reliable by the provision of one additional global parameter for each subband. Results based on our proposed method suggest that estimation errors on the order of 1 to 3 dB can be obtained on average, over a wide range of bit-rates; these results appear to hold for a range of images, block sizes and quality layer densities.