Image forming device, image forming method, computer program, and recording medium

摘要

An image forming device includes a quantization unit (3) which quantizes each pixel of an M-level gradation input image into one of N levels (M > N >/= 2) through an error diffusion process. An operation unit (8,9) performs a predetermined operation on the gradation value of the target pixel before quantization when the gradation value of the target pixel is equal to a specific concentration, the operation being dependent on the position of the target pixel. In one embodiment the addition or subtraction of predetermined values generates a blank dot or a middle dot in a solid small dot of an output image. In another embodiment the gradation scale of a multilevel image forming device is subdivided into N-1 portions and the quantization thresholds depend on the gradation values according to sloped characteristics in each portion of the gradation scale. <IMAGE>