Patent ID: 6266157
Filing Date: 2001-07-24
Classification: H04N

Abstract:
A method of quantizing image pixels, in which for an image formed by a plurality of pixels, each pixel representing an optical density of the image at a location within the image, and having an original value associated therewith selected from of a set of optical density values having an number of members larger than a desired output set of optical density values, the steps comprising:storing a set of values .DELTA., representing a gray difference that a mark on a print substrate will provide for a selected printer, each value of .DELTA. corresponding to a printing pattern of pixels;receiving a pixel to be quantized, and a set of neighboring pixels;adding to the original value of each said pixel to be quantized, an error value resulting from quantization of any previous pixels, to generate a modified pixel value;using said pixel to be quantized and said set of neighboring pixels, together forming a printing pattern of pixels, to identify a value of .DELTA. to be used for quantization and error calculation;quantizing said modified pixel value by comparison to a fraction of said identified value of .DELTA., and selecting a member of the desired output set of optical density values as an output signal;calculating a halftoning error using said output signal, said identified value of .DELTA. and said modified pixel value; anddistributing said halftoning error to a a pre-selected set of pixels.