PURPOSE: To subject a noticed picture element to the continuity processing to peripheral picture elements to improve the quality of an outline extraction picture by comparing the prescribed noticed picture element with peripheral picture elements to perform the binary processing and extracting the outline of the picture and arranging binary picture data in a matrix to discriminate the continuity between the prescribed noticed picture element and peripheral picture elements.

CONSTITUTION: A matrix of a prescribed space due to a shift register, a line memory, or the like is formed in an outline extracting circuit 2 of a picture outline extracting device, and the variable density picture of a document read by a photoelectric transducer or the like is subjected to A/D conversion and is inputted to the circuit 2 as multilevel data to form the space matrix. Picture element data E in the center of the matrix of this circuit 2 is denoted as the noticed picture element, and the outline extraction operation processing is performed between the noticed picture element and four peripheral picture elements B, D, F, and H, and operation data SD is inputted to a comparator 11 of a binarizing circuit 3. Data SD and a threshold S1 for outline detection are compared with each other, and outline data SB indicating whether binarized data is the outline or not is processed in a continuity processing circuit 4, thus obtaining outline output data.