On the limits of perceptual quality measures for enhanced underwater images

TL;DR

This paper critically evaluates existing perceptual quality measures for underwater image enhancement, revealing their inadequacies and highlighting the need for better evaluation metrics in this domain.

Contribution

The study systematically reviews and assesses the effectiveness of current colour accuracy and no-reference quality measures for underwater images, exposing their limitations.

Findings

No-reference quality measures do not reliably rate underwater image quality.

Commonly used measures like UIQM and UCIQE have significant shortcomings.

Existing metrics are insufficient for consistent evaluation of enhancement methods.

Abstract

The appearance of objects in underwater images is degraded by the selective attenuation of light, which reduces contrast and causes a colour cast. This degradation depends on the water environment, and increases with depth and with the distance of the object from the camera. Despite an increasing volume of works in underwater image enhancement and restoration, the lack of a commonly accepted evaluation measure is hindering the progress as it is difficult to compare methods. In this paper, we review commonly used colour accuracy measures, such as colour reproduction error and CIEDE2000, and no-reference image quality measures, such as UIQM, UCIQE and CCF, which have not yet been systematically validated. We show that none of the no-reference quality measures satisfactorily rates the quality of enhanced underwater images and discuss their main shortcomings. Images and results are available at https://puiqe.eecs.qmul.ac.uk.