The use of intensity-dependent weight functions to “Weberize” L2 -based methods of signal and image approximation

We consider the problem of modifying L2-based approximations so that they “conform” in a better way to Weber’s model of perception: Given a greyscale background intensity I> 0 , the minimum change in intensity ΔI perceived by the human visual system is ΔI/ Ia= C, where a> 0 and C> 0 are constants. A “Weberized distance” between two image functions u and v should tolerate greater (lesser) differences over regions in which they assume higher (lower) intensity values in a manner consistent with the above formula. In this paper, we Weberize the L2 metric by inserting an intensity-dependent weight function into its integral. The weight function will depend on the exponent a so that Weber’s model is accommodated for all a> 0. We also define the “best Weberized approximation” of a function and also prove the existence and uniqueness of such an approximation.