Mechanism analysis of highly overlapped interpolation contrast enhancement

The pointwise sampling algorithm has been used in adaptive contrast enhancement (ACE) for nearly three decades. To overcome its computational overhead, various stepwise sampling algorithms have been proposed, including the highly overlapped interpolation contrast enhancement (HOICE) algorithm that addresses the artefacts, such as image distortion and blocking effects, of other stepwise sampling algorithms while keeping the advantage of speed. However, HOICE's internal mechanism has not been compared with traditional pointwise algorithms, which may affect the scope of its future application. The authors establish a bridge between traditional pointwise sampling and HOICE: they first mathematically analyse the internal mechanism of two typical sampling algorithms (pointwise and HOICE); and then quantitatively demonstrate the similarities between these two kinds of algorithms. Moreover, the results of quantitative measurement suggest that HOICE has an advantage over the pointwise algorithm in reducing the distortion along image edges. Therefore HOICE has the advantages of both pointwise and other stepwise algorithms making it a reliable sampling algorithm for ACE.