Patent ID: 7315401

Claim:
A quantization apparatus for performing a quantization process by using an error diffusion method, wherein said quantization apparatus prints each pixel of an image with ink droplets having at least two different sizes in accordance with an output value of quantized image data, comprising: converting means for converting a pixel value of interest containing a diffused error into an output value corresponding to a value range to which the pixel value of interest belongs; and diffusing means for diffusing, as an error, a difference between the output value converted by said converting means and the pixel value of interest to pixels neighboring the pixel of interest, wherein at least one intermediate range, except for a range including a maximum pixel value and a range including a minimum pixel value, does not contain any output value corresponding to the intermediate range, wherein an upper limit of at least one intermediate range is substantially median between a lower limit of the intermediate range and an output value corresponding to the intermediate range, and wherein the output value corresponding to the intermediate range is recorded with an ink droplet having a smaller size of the at least two different sizes.