Patent ID: 7362473

Claim:
An image processing device for processing each pixel of an image to convert multitone image data into data of a format represented by the dot on-off state for each said pixel, along a raster consisting of a row of said pixels, said device comprising: tone error calculating unit that, during said conversion for each said pixel, calculates tone error corresponding error in tone representation occurring in a pixel of interest having undergone said conversion; matrix storage unit that stores a plurality of types of error diffusion matrices of different diffusion range size, said error diffusion matrices indicating weights for each pixel, for diffusing said tone error into unprocessed pixels neighboring said pixel of interest; matrix selection unit that selects a single error diffusion matrix from among said stored plurality of types of error diffusion matrices, depending on the image data for said pixel of interest; error diffusion unit that diffuses said tone error into peripheral pixels adjacent to said pixel of interest, in accordance with said selected matrix; and data conversion unit that converts said image data into data of a format represented by the dot on-off state for said pixel of interest, while considering said tone error diffused from processed peripheral pixels, and wherein said matrix storage unit has prestored therein at least one error diffusion matrix with a directivity factor, which indicates the extent of diffusion of said tone error in said raster direction, to be 2.0 or higher, as said error diffusion matrix having a widest diffusion range in said raster direction.