Patent ID: 8184917
Filing Date: 2012-05-22
Classification: H04N

Abstract:
1. An image processor for processing each pixel of a halftone image by sequentially setting each pixel as a target pixel, each pixel being defined by a pixel density representing a gradation level of each pixel, the image processor comprising: a converting unit that converts the pixel density of the target pixel into a first output value, the first output value indicating whether or not a dot is formed on the target pixel; an error data calculation unit that calculates error data of the target pixel, the error data corresponding to a difference between the first output value and the pixel density; a compression unit that irreversibly compresses the error data of the target pixel, partial data of the pixel density being lost from the error data when irreversibly compressing the error data; an error buffer that stores the compressed error data of the target pixel and a plurality of sets of compressed error data for a plurality of processed pixels, the plurality of processed pixels having been processed by the converting unit, the error data calculation unit, and the compression unit prior to the target pixel; a decompression unit that reads a plurality of sets of compressed error data for a plurality of peripheral pixels with respect to a next target pixel from the error buffer and decompresses the compressed error data sets for the plurality of peripheral pixels, the next target pixel being processed next to the target pixel; a density correction unit that corrects a pixel density of the next target pixel based on the decompressed error data sets for the plurality of peripheral pixels, the converting unit converting the corrected pixel density of the next target pixel into a second output value, the second output value indicating whether or not a dot is formed on the next target pixel; and a data compensating unit that compensates the partial data.