Patent ID: 7555172

Claim:
A method of processing image data for a document processing system, comprising: receiving a digital representation of an original image from an image in put device, the digital representation including a plurality of pixels, each pixel having a grayscale value; dividing the digital representation into tiles, each tile including multiple pixels; creating a histogram for each tile based on the grayscale values of the multiple pixels in the corresponding tile; determining a whitepoint value of each tile based at least in part on the corresponding histogram; determining a blackpoint value of each tile based at least in part on the corresponding histogram; creating a whitepoint map by determining whitepoint values for each pixel in the digital representation by interpolating the determined whitepoint values of neighboring tiles and storing the whitepoint map in whitepoint memory; and creating a blackpoint map by determining blackpoint values for each pixel in the digital representation by interpolating the determined blackpoint values of neighboring tiles and storing the blackpoint map in blackpoint memory.