Patent ID: 7869095

Claim:
A method of halftoning an image using an error diffusion process, comprising: (a) generating an upper threshold level and a lower threshold level; (b) choosing a region number parameter; (c) selecting an unmodified input pixel value from the input image and modifying the unmodified input pixel value with a diffused error value; (d) comparing the modified input pixel value from the input image to the upper and lower threshold levels; (e) outputting a first pixel value when the modified input pixel value is below the lower threshold level; (f) outputting the first pixel value when the modified input pixel value is below the upper threshold level and above the lower threshold level and the modified input pixel value divided by the region number parameter, modulo 2, equals zero; (g) outputting a second pixel value, the first pixel value being different from the second pixel value, when the modified input pixel value is below the upper threshold level and above the lower threshold level and the modified input pixel value divided by the region number parameter, modulo 2, is not zero; (h) outputting the second pixel value when the modified input pixel value is above the upper threshold level; (i) determining a difference between the output pixel value and the modified input pixel value to generate an error; and (j) diffusing the error, as error values, to neighboring pixels.