Patent ID: 6628837
Filing Date: 2003-09-30
Classification: G06K

Abstract:
A method for generating image data for a hardcopy document, comprising:identifying a primary set of symbol data; the primary set of data providing a first channel of human readable information to be rendered on the hardcopy document; computing a secondary set of encoding data from the primary set of symbol data; the secondary set of encoding data providing a second channel of machine readable information to be rendered on the hardcopy document; wherein, for a selected line of the primary set of symbol data having an ordered set of c1, c2, c3, . . . ciâˆ’1, ci, ci+1, . . . cn symbols, said computing further comprises: sequentially computing a hash of each of the symbols of the selected line with a state change function H; the state change function H producing a hash hi that is at least a function of the current symbol in the selected line ci and the preceding computed hash hiâˆ’1; and computing a set of guard values for each of the symbols of the selected line with a guard extractor function G; the guard extractor function G producing a guard value gi that is at least a function of the computed hash hi; the computed set of guard values defining the second set of encoding data for the selected line.