A new contrast enhancement method for color images is presented. The method is based on local color analysis even though the actual contrast adjustment phase is spatially global. The adjustment parameters, however, vary depending on the location in the color space. The color gamut is divided into fragments, which are analyzed and adjusted separately. Color variables used for color space division are different from those used for image adjustment.The new contrast enhancement method proved to be a useful color adjustment tool. It can well be used together with traditional global color image enhancement methods. In most cases it is capable of enhancing contrast even when other color adjustments have already been made.The method was tested with a special preprocessed image set where all images had good gray balance and contrast, right overall lightness level and RGB histograms covering the full tonal range. Analysis of this test image set showed that despite the extraordinary starting point, additional contrast enhancement was possible. Most photographic color images had at least some potential to benefit from this method. In practice, the utilization of this potential led to significant improvement of visually assessed image quality in more than half of the cases.
Pekka Laihanen, "A Contrast Enhancement Method Based on Analysis of Local Color Information" in Proc. IS&T 8th Color and Imaging Conf., 2000, pp 207 - 210, https://doi.org/10.2352/CIC.2000.8.1.art00038