Apparatus outputting quantized image data, selecting from filters with different error spreading effects

摘要

An image processing apparatus includes an edge detector for detecting whether or not a target pixel of an input image signal is at an edge portion of a discontinuous density image; a first quantizer for generating quantized image data with respect to the target pixel by using a first error spreading filter having a relatively high error spreading effect, such that a density error between the input image signal and an output multilevel image signal is incorporated in "m" neighboring pixels surrounding the target pixel; a second quantizer for generating quantized image data with respect to the target pixel by using a second error spreading filter having a relatively low error spreading effect, such that a density error between the input image signal and the output multilevel image signal is incorporated in "m" neighboring pixels surrounding the target pixel; and a selector for selecting either the quantized image data generated by the first quantizer or the quantized image data generated by the second quantizer in accordance with the result of a detection made by the edge detector.