Smoothing DCT Compression Artifacts

Abstract

mage compression based on quantizing the d image in the discrete cosine transform (DCT) omain can generate blocky artifacts in the outs a put image. It is possible to reduce these artifact nd RMS error by adjusting measures of block g t edginess and image roughness, while restrictin he DCT coefficient values to values that would d i have been quantized to those of the compresse mage. We also introduce a DCT coefficient . amplitude adjustment that reduces RMS error INTRODUCTION n i Lossy image compression in the DCT domai s achieved by the quantization of the DCT t i coefficients. The quantization of a single coefficien n a single block causes the reconstructed image to p differ from the original image by an error image roportional to the associated basis function in that - n block. Our goal here is to try to reduce the blocki ess without reducing the accuracy of the reconstruction. The sum of squared differences between adjat cent block edge pixels is a measure of blockiness hat te...