Patent ID: 8045809

Claim:
An image forming apparatus, comprising: a random dither processing unit that performs random dither processing of converting input N-values image data to M-values image data; a non-transitory memory configured to store the input N-values image data; a flag setting unit that sets a flag that designates an addition of a non-periodic component to each of quantization threshold values; a threshold-value adding unit that adds a non-periodic component to the quantization threshold values based on a magnitude of the quantization threshold values in different threshold value levels with respect to a target pixel in the quantization threshold values; and a controlling unit that determines whether the threshold-value adding unit is to add the non-periodic component, wherein the controlling unit determines whether the threshold-value adding unit is to add the non-periodic component depending on whether the magnitude of the quantization threshold values that correspond to different threshold value levels in the target pixel satisfies a predetermined relation.