Visual assessment of variable-resolution imagery.

A technique is described for producing variable-resolution images whose spatial detail decreases as a function of distance from their centers. These images can be matched in some sense to the normal spatial inhomogeneities of the human visual system, as well as to various abnormalities in spatial discrimination. A set of images was generated with a series of linear distortion functions whose low-pass characteristics differed at both the center and the periphery of the image as well as across the image. A forced-choice procedure was used to determine which test images were indistinguishable from unprocessed versions of themselves. Certain of the threshold distortion functions are compared with eccentricity scaling functions that have been used by others to characterize various aspects of peripheral vision. Finally, the concept of locally band-limited spaces is discussed, and an efficient sampling technique based on the concept is described. This technique can be used to generate an image that, under certain conditions, is visually equivalent to an otherwise identical image containing significantly more information.