Efficient Operator for Local Energy Measurements to Enhance an Image Signal
For real-time imaging with digital video cameras and high-quality display with TV systems, the obtained picture quality including visibility of details, local contrast, and absence of artifacts, is very important to ensure user quality acceptance. We present a multi-window real-time high-frequency enhancement scheme, in which gain is a non-linear function of the detail energy. Then we discuss the computation of commonly used local energy measurements and show that a selection of those measurements can be calculated efficiently. In our first contribution, we propose a new local energy measurement APS that can be calculated more efficiently than the existing metrics in a 2-D-separable fashion. In addition, we also show that the new APS measurement gives better performance than standard energy measurements. The second contribution is the use of local contrast and a modified contrast gain formula that can substantially improve the overall algorithm performance, especially when a high-level contrast enhancement is desired. Our algorithm trades off between added contrast and “halo” artifacts, resulting in a good balance between visibility of details and an acceptable level of artifacts. The new scheme can be successfully applied to cameras and TV systems to improve their visual quality.