On the limits of perceptual quality measures for enhanced underwater images
This addresses a critical bottleneck for researchers in underwater imaging by highlighting the lack of reliable evaluation metrics, which is incremental as it systematically validates existing measures rather than proposing new ones.
The paper tackles the problem of evaluating underwater image enhancement methods by reviewing and validating existing no-reference quality measures, showing that none satisfactorily rate enhanced underwater images.
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.