PURPOSE: To smooth the hatched parts of characters and graphics, etc., and to extract contours by a simple method.

CONSTITUTION: In this picture processing method for developing pictures constituted of the set of dots on a bit map memory 1, accessing the bit map memory 1 and processing the pictures, in the case of magnifying a hatched line developed on the bit map memory to N times, (N-1) pieces of the hatched lines obtained by successively shifting the magnified hatched line to a left side and a lower side for a predetermined dot number by the number corresponding to the inclined angle of the hatched line are generated when the hatched line is inclined from an up right side to a down left side and (N-1) pieces of the hatched lines obtained by successively shifting the magnified hatched line on a right side and on the lower side for the predetermined dot number by the number corresponding to the inclined angle of the hatched line are generated when the hatched line is inclined from an up left side to a down right side. The logical sum of logical values for indicating the respective dots of the respective hatched lines generated for (N-1) pieces and the magnified hatched line are ORed and an arithmetic result is written on the bit map memory 1.