14. A method of modifying a first document including content and a barcode encoding data related to the first document, said barcode comprising barcode elements each having a predetermined form, said method comprising the steps of: detecting a plurality of the barcode elements of the barcode in a representation of the first document; determining a visual difference between each of the detected barcode elements and the predetermined form of the barcode element; and removing at least some of the degradation of the content of the first document based on the determined visual difference, in order to compensate for degradation of the first document, wherein at least the determining and removing steps are implemented using a processor.
14. A method of modifying a first document including content and a barcode encoding data related to the first document, said barcode comprising barcode elements each having a predetermined form, said method comprising the steps of: detecting a plurality of the barcode elements of the barcode in a representation of the first document; determining a visual difference between each of the detected barcode elements and the predetermined form of the barcode element; and removing at least some of the degradation of the content of the first document based on the determined visual difference, in order to compensate for degradation of the first document, wherein at least the determining and removing steps are implemented using a processor. 20. The method of claim 14 , wherein the barcode elements are dots and the 2-D barcode consists of dots modulated spatially about nominal grid positions.