  Full-reference image quality metrics (FR-IQMs) aim to measure the visual
differences between a pair of reference and distorted images, with the goal of
accurately predicting human judgments. However, existing FR-IQMs, including
traditional ones like PSNR and SSIM and even perceptual ones such as HDR-VDP,
LPIPS, and DISTS, still fall short in capturing the complexities and nuances of
human perception. In this work, rather than devising a novel IQM model, we seek
to improve upon the perceptual quality of existing FR-IQM methods. We achieve
this by considering visual masking, an important characteristic of the human
visual system that changes its sensitivity to distortions as a function of
local image content. Specifically, for a given FR-IQM metric, we propose to
predict a visual masking model that modulates reference and distorted images in
a way that penalizes the visual errors based on their visibility. Since the
ground truth visual masks are difficult to obtain, we demonstrate how they can
be derived in a self-supervised manner solely based on mean opinion scores
(MOS) collected from an FR-IQM dataset. Our approach results in enhanced FR-IQM
metrics that are more in line with human prediction both visually and
quantitatively.
