GRADATION CONVERSION APPARATUS, IMAGE PROCESSING APPARATUS, PRINTING APPARATUS, GRADATION CONVERSION METHOD AND PROGRAM

摘要

PPROBLEM TO BE SOLVED: To solve the problem wherein pseudo contour, sweeping, texture or other phenomena due to transient response of a feedback loop system appear on a printing screen. PSOLUTION: The gradation conversion apparatus is proposed which converts an image intensity signal having gradation of an m-value (m being an integer) into an image intensity signal having gradation of an n-value (n being an integer smaller than m), and adds a propagation error E generated in the preceding gradation conversion to a next image intensity signal to correct gradation. The apparatus has: (a) a correction amount comparator for comparing a propagation error E to be used for the next gradation conversion with a reference conversion amount K; and (b) an error correction control unit for using the propagation error E for gradation correction of the image intensity signal to be used for the next gradation conversion, if the propagation error E is not less than the reference correction amount K, and for not using the propagation error E for gradation correction of the image intensity signal to be used for the next gradation conversion, but for adding the propagation error E to a conversion error CE to be generated in the next gradation conversion, if the correction value is smaller than the reference correction amount K. PCOPYRIGHT: (C)2006,JPO&NCIPI