Morphological rational multi-scale algorithm for color contrast enhancement

Contrast enhancement main goal consists on improving the image visual appearance but also it is used for providing a transformed image in order to segment it. In mathematical morphology several works have been derived from the framework theory for contrast enhancement proposed by Meyer and Serra. However, when working with images with a wide range of scene brightness, as for example when strong highlights and deep shadows appear in the same image, the proposed morphological methods do not allow the enhancement. In this work, a rational multi-scale method, which uses a class of morphological connected filters called filters by reconstruction, is proposed. Granulometry is used by finding the more accurate scales for filters and with the aim of avoiding the use of other little significant scales. The CIE-u’v’Y’ space was used to introduce our results since it takes into account the Weber’s Law and by avoiding the creation of new colors it permits to modify the luminance values without affecting the hue. The luminance component (‘Y) is enhanced separately using the proposed method, next it is used for enhancing the chromatic components (u', v’) by means of the center of gravity law of color mixing.