PURPOSE: To attain extraction of features such as terminal points, flection points, etc. by detecting a series of pairs of substrokes to be paired and deleting paired substrokes serves as connectors to extract strokes of a character pattern.

CONSTITUTION: A thick line shows the boundary between white and black areas, and the information on this boundary line is stored to a memory. The parts enclosed by chain lines show the substrokes (B1, B2), etc., and the information on each substroke is also stored to the memory. The head coordinate data on a substroke B1 is first loaded to decide the scan direction, and the coordinates are shifted. Now the coordinates are shown in a black area and equal to those of a substroke B2. Therefore it is decided that both strokes B1 and B2 are paired with each other, and the data is stored to repeat the processing. When the processing is over, new strokes corresponding to the paired substrokes are obtained. The stroke data is searched and the data on the paired substrokes is erased as long as ≥2 substrokes are related with each other.