1. A method for enhancing the image contrast of a digital mammographic image, comprising using a computer to perform steps of: accessing the digital mammographic image; segmenting the digital mammographic image to identify a region of interest based on gray level of dense breast tissue; generating a first histogram of the segmented digital mammographic image; generating a global contrast enhanced histogram by applying histogram equalization to the first histogram; generating a detail contrast enhanced histogram for the region of interest by applying spatial correlation histogram equalization to the first histogram using spatial relationships of pixels in the region of interest, thereby preserving gray level detail at a tail end of the detail contrast enhanced histogram; generating a combined histogram using the global contrast enhanced histogram and the detail contrast enhanced histogram; and using the combined histogram to generate a contrast-enhanced digital mammographic image.