PURPOSE: To store many points through reduced capacity of storage area, by storing only the 1st profile point of a graph with X and Y coordinates and storing linked direction signal codes of points linked to each point as to succeeding points.

CONSTITUTION: A screen is scanned with a reading line sensor 1, a light input from the screen is received and binary coded at a binary coding circuit 2 and the signal is inputted to a picture processor 3 corresponding to the signal train via a data bus. A pulse from an oscillator 4 is applied to the sensor 1 and an X axis coordinate counter 5 and the carry signal of the counter 5 is applied to a Y axis coordinate counter 6. The present coordinates of the counters 5 and 6 is applied to the processor 3 and through the control of a program in the processor 3, 8-direction linking for black bit and 4-direction linking for white bit can be decided. Only the 1st profile point is stored at the X and Y coordinates and the succeeding points are stored for the linking direction signal codes only.