PURPOSE: To provide a method and a means for incorporating digital data that can be read by a machine in the gray scale image inconspicuously. CONSTITUTION: In a gray scale image formation system 21, a modulator 22 modulates a gray scale image sample into a low contrast regarding the foreground and background of a previously selected image according to binary data and applies it a gray scale sampled value which fluctuating between right adjacent gray scale levels as a function of the binary data to a printer 23. The binary data incorporated in a print image are loaded to a buffer 25 which operates or does not operate with a control signal and when the control signal has true logical level, an AND gate 26 performs gate control over clock pulses at a specific frequency and sends them to the buffer 25, which applies the binary data to the modulator 22 in sequence at the frequency.
ART REINFORCED PSYCHOPHYSICALLY FOR INCORPORATING DIGITAL DATA READABLE WITH MACHINE INTO GRAY SCALE IMAGE