A method is provided for encoding two-dimensional frame codes comprising the steps of establishing first and second line bit sequences, determining an exclusive OR (XOR) logic value of the first and second code lines to obtain a two-dimensional matrix of XOR logic values and determining the two-dimensional frame codes using the matrix of XOR logic values.
CROSS REFERENCES
This application is related to concurrently filed, commonly assigned U.S. patent application Ser. No. 09/465,990, entitled "A Machine-Readable Record With a Two-Dimensional Lattice of Synchronization Code Interleaved With Data Code," by David L. Hecht.
A specific bit pattern (or set of bit patterns) that have particular frequency and length requirements is used to remove low-frequency, visually observable structure from rendered embedded digital data. In use, the pattern is replicated enough times to be able to XOR with the data before rendering as glyphs, or the like. On decoding (reading), the read data is XOR'd again to recover the original data.
