Patent ID: 7612916

Claim:
An image processing device, comprising: a memory configured to store an input image; an inverted image generator configured to generate an inverted image, the inverted image corresponding to a predetermined part of the input image; a target image generator configured to generate a target image by combining, the inverted image and the input image; a quantization unit configured to quantize the target image, in accordance with the error diffusion method; an image extractor configured to extract an output image from the quantized target image, the output image corresponding to the input image; and an output unit configured to output the output image extracted by the image extractor; wherein the target image generator generates the target image including at least one of a first inverted image and a second inverted image, the first inverted image being an image axially symmetrical to the input image, the axis being defined by a start point of the quantization and a direction in which the quantization proceeds, the first inverted image having a length (or a width) of a-line, a being a predetermined positive integer; and the second inverted image being an image axially symmetrical to the input image, the axis being defined by a start point of the quantization and a direction orthogonal to a direction in which the quantization proceeds, the second inverted image having a length (or a width) of b-line, b being a predetermined positive integer.