PURPOSE: To realize a pattern extracting method where the form of a pattern is extracted basing on the circumferential length and the area of a part surrounded with the border line between the background of the pattern having a certain line width and this pattern, by extracting coordinates of this border line and operating the length of this border line and the area of the part surrounded by this border line.

CONSTITUTION: After the start of operation, a picture surface from which a pattern should be extracted is scanned in every line, and data of each point coordinates (x, y) is read into a picture processor 3 through a read line sensor 1 and a binary circuit 2, and the linkage in 8 directions such as upward, downward, left, right, and oblique directions is checked if an input picture is black bits and the linkage in four directions is checked if the input picture is white bits on a basis of the control of a program 7, and data are stored in a component storage part 8, an area storage part 9, a color storage part 10, and an outside circumferential coordinate storage part 11 respectively on a basis of these check results. Input pattern features are obtained from the form coefficient, the area, etc. of the input pattern based on these stored contents by calculation and are stored in an input pattern feature storage part 12 and are collated with contents of a registered pattern storage part 13 where features of patterns are stored preliminarily.