Enhancing the low quality images using Unsupervised Colour Correction Method

TLDR

Underwater images suffer reduced contrast and non‑uniform colour casts from light absorption and scattering, compromising image quality and the reliability of downstream processing. The study introduces an unsupervised colour‑correction method (UCM) to enhance underwater images. UCM balances colour, applies RGB contrast stretching (boosting red, reducing blue), and corrects HSI saturation and intensity to improve true colour and illumination, and is benchmarked against Gray World, White Patch, and histogram equalisation. UCM yields superior visual quality compared to the three baseline methods.

Abstract

Underwater images are affected by reduced contrast and non-uniform colour cast due to the absorption and scattering of light in the aquatic environment. This affects the quality and reliability of image processing and therefore colour correction is a necessary pre-processing stage. In this paper, we propose an Unsupervised Colour Correction Method (UCM) for underwater image enhancement. UCМ is based on colour balancing, contrast correction of RGB colour model and contrast correction of HSI colour model. Firstly, the colour cast is reduced by equalizing the colour values. Secondly, an enhancement to a contrast correction method is applied to increase the Red colour by stretching red histogram towards the maximum (i.e., right side), similarly the Blue colour is reduced by stretching the blue histogram towards the minimum (i.e., left side). Thirdly, the Saturation and Intensity components of the HSI colour model have been applied for contrast correction to increase the true colour using Saturation and to address the illumination problem through Intensity. We compare our results with three well known methods, namely Gray World, White Patch and Histogram Equalisation using Adobe Photoshop. The proposed method has produced better results than the existing methods.