PURPOSE: To set a two dimensional area with a memory equivalent to just one line by setting areas for (m) picture elements set previously in both the primary and secondary scan directions when the first picture element of a specific picture image area such as an edge area, etc. is extracted and then extracting a signal showing said setting action.

CONSTITUTION: An input edge signal S1 is compared with the threshold value Th that is set previously by a comparator 41. When the signal S1 is larger than the value Th, an edge deciding signal S2 is set at "1". Thus the writing is possible to an RAM45. When the signal S2 showing an edge area is detected, it is decided that the edge areas of (n×n) picture elements are set in both primary and secondary scan directions according to the value (n) set previously. Then the values corresponding to those set edge areas are set to the RAM45 and a flag counter 42.