Traditional quality measures for image coding, such as the peak signal
-to-noise ratio, assume that the preservation of the original image is
the desired goal. However, pre-processing images prior to encoding, d
esigned to remove noise or unimportant detail, can improve the overall
performance of an image coder. Objective image quality metrics obtain
ed from the difference between the original and coded images cannot pr
operly assess this improved performance. This paper proposes a new met
hodology for quality metrics that differentially weighs the changes in
the image due to pre-processing and encoding. These new quality measu
res establish the value of pre-processing for image coding and quantit
atively determine the performance improvement that can be thus achieve
d by JPEG and wavelet coders. (C) 1998 Elsevier Science B.V. All right
s reserved.