Image processing utilizing luminance-density conversion

摘要

Disclosed are an image processing method and apparatus for applying spatial filtering processing to n-bit multilevel image data, converting the processing image data to two-level or multilevel image data and converting the resulting image data to data capable of being expressed using high-resolution dots. The filtered image data is subjected to a luminance-to-density conversion and is further converted to two or four levels by a four-level/two-level conversion circuit which makes common use of circuitry for executing both two-level error diffusion processing and four-level error diffusion processing. The four-level/two-level conversion circuit clamps the error produced in four-level conversion processing to the number of significant bits of the error produced at execution of the two-level conversion processing. As a result, a common circuit can be used for both the two-level conversion processing and the four-level conversion processing.