A method for obtaining bitonal image data from a document obtains scanned color image data from at least two color channels and identifies, in the scanned color image data, at least one region of interest (R1) containing foreground content and background content. At least one threshold data value is obtained according to an image attribute that differs between the foreground content and the background content within the region of interest (R1). The scanned color image data of the document is converted to bitonal image data according to the at least one threshold data value obtained from the region of interest (R1).