Method of and apparatus for detecting pixels constituting dotted image area utilizing distance between change points of pixel values

摘要

Disclosed is an apparatus for detecting pixels in a dotted image area (dotted area pixels). Image data corresponding to each of the pixels is coded into one of a predetermined number of discrete values. The distance between change points at which the value of the pixel after the coding is changed from a first value to a second value is detected. Further, it is examined whether or not periodicity is recognized in the distance between the change points in the vicinity of a target pixel. If periodicity is recognized in the distance between the change points, it is judged that the target pixel may constitute a dotted image area./!