Disclosed is a method of decoding a first barcode and a second barcode, different from the first barcode. The barcodes have typically been printed on a page and are derived from image scanning. The first barcode comprises a plurality of marks modulated about a first grid to redundantly encode data and the second barcode comprising a plurality of marks modulated about a second grid. The method estimates (810) the first grid from a bitmap representation (805) of at least a portion of the page, using modulated marks contained therein. The method determines (820) a first barcode region from the first grid, the first barcode region being a portion of the first barcode, followed by estimating a second grid from the bitmap representation, using modulated marks contained therein. The method determines a second barcode region from the second grid, the second barcode region being a portion of the second barcode, and then decodes (830) the first and second barcode regions using the first and second grids respectively to derive the first and second barcodes.