13. Non-transitory computer readable media according to claim 11 whereby the texture feature is printed matter.
13. Non-transitory computer readable media according to claim 11 whereby the texture feature is printed matter. 14. Non-transitory computer readable media according to claim 13 whereby the predetermined printing method is intaglio printing and step a) comprises obtaining a first digital image of the at least one portion of the document when it is directionally illuminated at 90 degrees and obtaining a second digital image of the at least one portion of the document when it is directionally illuminated at an angle other than 90 degrees.