Patent ID: 8228560

Claim:
A method for contrast enhancement for digital images, comprising: filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable; receiving parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local brightening multipliers by applying the brightening response curve to the first filtered image; deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and processing the original image, comprising: subtracting the local darkening offsets from the original pixel color values to generate shifted color values; multiplying the shifted color values by the local brightening multipliers; and further multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.