A method for image processing in which an image of a bound document such as a book placed face-down on a document positioning plate is read and processed is provided. The method includes reading the bound document through the document positioning plate, displaying the read image, the read image having at least one of a shadow portion of a bound portion and a shadow portion of an edge portion, inputting information about a direction attribute of a rectangular area of the shadow portion in the displayed image, determining the direction attribute based on the input information, and correcting a density of the rectangular area based on the determined direction attribute.