PURPOSE: To identify half tone picture and letter picture and make picture output in proper dot pattern by detecting edges of graphics of density area above prescribed density in an inputted picture and detecting that it is a letter picture area by whether the density difference is above prescribed value.

CONSTITUTION: An analog signal is outputted according to the density of a picture by a picture reading device 5, and each picture element of the analog signal is converted to a digital signal by a digitalizing circuit 6 and outputted to an image memory 7 and an edge detecting circuit 8. Data of the whole picture is stored in the memory 7, and address of picture element of inner edge and outer edge is detected by the circuit 8, and the picture element address is stored in a memory 9. The picture element address stored in the memory 9 is inputted to an address generating circuit 10, and address of inner edge or outer edge of the edge is inputted from the circuit 10 to an identifying circuit 11. A letter picture element area is identified from density data stored in the memory 7 in the circuit 11, and picture is outputted from a dot pattern generating circuit 13 in proper dot pattern.