9. A non-transitory computer-readable storage medium having instructions stored thereon that, if executed by a computing device, cause the computing device to perform operations comprising: analyzing data corresponding to a security document in a frequency transform domain to obtain a predefined, machine-readable pattern, wherein the security document comprises a security pattern having a line structure in which line width or line spacing have been adjusted to convey the predefined, machine-readable pattern in the frequency transform domain, and wherein the security pattern is repeated across the security document; and controlling an action in based on the predefined, machine-readable pattern.
9. A non-transitory computer-readable storage medium having instructions stored thereon that, if executed by a computing device, cause the computing device to perform operations comprising: analyzing data corresponding to a security document in a frequency transform domain to obtain a predefined, machine-readable pattern, wherein the security document comprises a security pattern having a line structure in which line width or line spacing have been adjusted to convey the predefined, machine-readable pattern in the frequency transform domain, and wherein the security pattern is repeated across the security document; and controlling an action in based on the predefined, machine-readable pattern. 10. The computer-readable storage medium of claim 9 , wherein the action comprises reproduction of the security document.