1. A method for determining an optical waveform based on a plurality of print features of a selected marking of a document, the method comprising the steps of: obtaining optical image data representing the print features of the selected marking; correcting at least one of print contrast or reflectance of the print features in the optical image data using respective print contrast thresholds or reflectance thresholds to produce a converted pixel map of the selected marking, the pixel map containing an ordered sequence of values; and transforming the print features represented in the converted pixel map to a plurality of corresponding waveform features to produce the optical waveform of the selected marking, the corresponding waveform features including a plurality of spaced apart peaks representing respective optical signal levels of the print features.