Patent ID: 7532364
Filing Date: 2009-05-12
Classification: H04N

Abstract:
1. An image processing method for use in an image processing device that converts multi-gradation image data to low-gradation image data for outputting an image of a dot pattern that is formed by a high-density first part formed in a band shape by dots connected in a predetermined direction and a low-density second part formed by randomly arranged dots, the image processing device including a dither processing unit and an error diffusion processing unit, the method comprising: the dither processing unit performing dither processing to convert multi-gradation image data ranging from a gradation value representing a maximum density to a predetermined gradation density to the gradation value representing the maximum density or the predetermined gradation density by using a threshold value table in which dither threshold values are arrayed to realize a line of dots connected in a predetermined direction with its width gradually increasing, and maintaining multi-gradation image data having lower density than the density represented by the predetermined gradation density at original gradation values; and the error diffusion processing unit then performing error diffusion processing on the multi-gradation image data having lower density than the density represented by the predetermined gradation density and the dither-processed data.