Non-linear locally-adaptive video contrast enhancement algorithm without artifacts

For real-time imaging with digital video cameras and high-quality display with TV systems, visibility of details is very important to ensure user quality acceptance. Many complex scenes require local contrast improvements that should bring details to the best possible visibility. However, local enhancement methods mainly suffer from ringing artifacts and over-emphasizing noise. We present a multi-window real-time high-frequency enhancement scheme, in which gain is a non-linear function of the detail energy. Our algorithm controls perceived sharpness, ringing artifacts (contrast) and noise, resulting in a good balance between visibility of details and non-disturbance of artifacts. The overall quality enhancement is based on a careful selection of the filter types for the multi-band decomposition and a detailed analysis of the signal per frequency band. The advantage of the proposed technique is that details in images become more visible without introduction of annoying artifacts. The new scheme can be successfully applied to cameras and TV systems to improve their contrast.