1. An image processing device comprising: a reading unit which reads a document and generates an image file representing an image of the read document; a graphics area extraction unit which extracts a graphics area in the image represented by the image file; a writing area extraction unit which extracts a writing area in the image represented by the image file; a character string extraction unit which extracts a character string present in the graphics area extracted by the graphics area extraction unit; a text extraction unit which extracts, from the writing area extracted by the writing area extraction unit, text that includes the same character string as the character string extracted by the character string extraction unit; and a document data generation unit which generates document data representing a document containing the graphics area extracted by the graphics area extraction unit and the text extracted by the text extraction unit.