Image-dependent color saturation correction in a natural scene pictorial image

摘要

A method and apparatus for image-dependent color saturation correction in natural scene images in electronic documents is provided, wherein an input image is converted (100) from its original color space definition to a luminance-hue-saturation color space, such as HSV space, where S has a strong correlation to perceived saturation. That saturation component of the signal is averaged (102) over the image for at least a region of its input value range corresponding to brightness, and the determined average is compared (104) to a threshold selected to represent desirable saturation level. If saturation is less than target saturation, a filtering function (110) is selected, operable on the image to enhance saturation as a function of the average saturation and desired saturations. Otherwise, no change is made to the image. Since altering saturation of an image in HSV space will tend to alter luminance of the image, subsequent to filtering the image to enhance saturation, the image is refiltered to reduce luminance as a function of the original luminance and the luminance of the saturation-enhanced image.