Patent ID: 6850340

Claim:
An image data processing method for processing original image data that is bit mapped in a main-scanning direction X and a sub-scanning direction Y, the method comprising: first multiplying first linearly aligned dots of odd lines in the main-scanning direction X of the original bit mapped image data by a positive integer Dy to generate Dy lines of linearly aligned dots adjoining each other in the sub-scanning direction Y as a first group of the sub-scanning direction Y; second multiplying second linearly aligned dots of even lines in the main-scanning direction X of the original bit mapped image data, which follow the first linearly aligned dots, by a positive integer Ry to generate Ry lines of linearly aligned dots adjoining each other in the sub-scanning direction Y as a second group of the sub-scanning direction Y, wherein the integers Dy and Ry are determined based on a ratio DPIin/DPIout between an image resolution of an input original image DPIin and an image resolution of an output image DPIout, and Dy and Ry satisfy (Dy+Ry)/2=DPIin/DPIout; and multiplying further following linearly aligned dots in the main-scanning direction X of the original bit mapped image data by repeating said first and second multiplying.