Enhancement of Very Low Light Images Using the YIQ Space Based on the CLAHE and Sigmoid Mapping with High Colour Restoration

Low-light image enhancement is a branch of digital image processing and is of great importance in many applications: aerial images, tracking, medical imaging and other applications.Therefore, this study aims to enhance the very low light images by relying on contrast limited adaptive histogram equalisation (CLAHE) with non-leaner sigmoid mapping based on YIQ colour space.Thus, the lighting component (Y) has been enhanced using CLAHE and sigmoid mapping, and the colour compound (IQ) has been treated via colour restoration.Color conversions are used to reduce any color error after enhancement, as the lighting component can be processed using CLAHE from the lighting component only.Two quality measures, namely, perception-based image quality evaluator (PIQE) and entropy (EN) were adopted to determine the efficiency of improvement.The proposed method was compared with several other methods, and the results were analysed.The findings indicate that the proposed method increased the lighting and restored the colours; it obtained the highest values for PIQE (34.598) and EN (7.025).