Patent ID: 6407825
Filing Date: 2002-06-18
Classification: H04N

Abstract:
A method for modifying an input image having an (x,y) array of input pixels, each pixel having an input colorant amount for one or more color channels to form an output image with output colorant amounts, said output image being suitable for printing on a digital printing device having two or more printing levels, comprising the steps of:a) determining an average total pixel colorant amount in a neighborhood of an input pixel in the input image; b) determining a colorant reduction amount for each color channel of the input pixel responsive to the input colorant amount, the average total pixel colorant amount in a neighborhood of the input pixel, and a threshold colorant amount; c) determining an output colorant amount for each color channel of the input pixel responsive to the colorant reduction amount, the input colorant amount, and a spatially periodic dither signal, so that an average output colorant amount in a neighborhood of each output pixel in the output image is constrained to be less than the threshold colorant amount; and d) repeating steps a) through c) for each pixel in the input image.