A new methodology for the determination of an objective metric for sti
ll image coding is reported. This methodology is applied to obtain a p
icture quality scale (PQS) for the coding of achromatic images over th
e full range of image quality defined by the subjective mean opinion s
core (MOS), This PQS takes into account the properties of visual perce
ption for both global features and localized disturbances. PQS closely
approximates the MOS, with a correlation coefficient of more than 0.9
2, as compared to 0.57 obtained using the conventional weighted mean-s
quare error (WMSE). Extensions and applications of the methodology and
of the resulting metric are discussed.