Halftone area separation method

Abstract

Abstract PURPOSE:To attain exact dot separation by using a local two-dimensional extremum detection pattern to detect the extremum of a picture element of an input picture and detecting a dot part by using a local two-dimensional dot detection pattern based on the result of this pole detection. CONSTITUTION:An input picture signal part 1 executes the raster scan of the original picture and converts the picture to a digital multi-level input picture signal composed of a luminance signal corresponding to a density level. An extremum detection part 2 applies a matrix composed of MXM picture elements to the respective picture elements of the picture sent from the signal part 1, and detects whether the central picture elements of the matrix is an extremum to show the projecting part or recessing part of a density change or not. A dot area detection part 3 counts the number of the extremum picture elements, which are detected by the detection part 2, showing the projecting and recessing parts for the unit of a block composed of NXN (N>M) picture elements and detects the dot area. An output picture signal part 4 outputs the output of the respective picture elements as a signal corresponding to the dot or as a signal corresponding to a linear picture, based on the result of the dot area detection in the detection part 3.

Inventors

• 👤 Hideyuki Watanabe
• 👤 英行 渡辺

Bibliographic Details