Patent ID: 6553151
Filing Date: 2003-04-22
Classification: H04N

Abstract:
An image forming apparatus with an image sensor for scanning a document to produce an electric signal representative of an image from the document, comprising:a converter for converting said electric signal to produce image data with a predetermined number of bits; a shading memory unit for storing said image data on a pixel by pixel basis from a least significant address to a most significant address scanned during a first mode operation with said converter, and for storing shading factors each corresponding to each pixel from said image data; a controller for sequentially reading said image data stored from the least significant address to the most significant address of said shading memory unit during said first mode of operation, calculating each shading factor for each pixel by dividing a preset maximum brightness value by said image data sequentially read from said shading memory unit, recording the shading factors in said shading memory unit, and for outputting the shading factors stored in said shading memory unit corresponding to each pixel of said image data produced by said converter during a second mode of operation; a shading compensation unit for multiplying each pixel of said image data produced from said converter by a corresponding one of said shading factors during said second mode of operation to produce shading-compensated image data; and a half-tone processing unit for producing a half-tone image data from said shading-compensated image data produced from said shading compensating unit.