Image processing apparatus and method for multi-level image signal

An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal in the form of a bi-level image signal, the image processing apparatus comprising:

• A) a screened-halftone pattern detecting circuit for detecting the screened-halftone pattern by using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels;
• B) a screened-halftone counter for counting the screened-halftone pattern detection state on each pixel in the succession of pixels;
• C) a continuous-tone pattern detecting circuit for judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel;
• D) a continuous-tone counter for counting the continuous-tone pattern detection state on each pixel in the succession of pixels;
• E) a filter for filtering the image signal of the target pixel gradually on the basis of different characteristics in accordance with either or both of the outputs of the two counters;
• and
• F) a means for bi-level-quantizing the output of the filter.