Chromatic Weibull Tone Mapping for Underwater Image Enhancement

Image enhancement is often used to alleviate the low contrast, blurring and colour reduction effects, common in underwater imagery. Tone Mapping, a particularly simple yet elegant enhancement technique improves image quality by modifying image histograms to a more desirable tonal distribution. In previous work, we presented our novel chromaticity-preserving algorithm, Weibull Tone Mapping (WTM), that can simplify custom tonal manipulations, to increase conspicuousness of image features. In this paper, we present a natural non-chromaticity preserving counterpart, in which the WTM tone map is applied to all colour channels (R,G,B). We demonstrate, as before, that user's prefer WTM to unenhanced images. However, contrary to prior work, our non-chromaticity preserving WTM is less preferred to custom tonal manipulations. Thus, how we map the colour aspect of images (given a brightness only tonal adjustment) has a significant impact on users' subjective preference judgements.