1. An image-reading apparatus that reads an image comprising: a document determining unit that determines any one or both of a type of document and a shape of a document; a detection-method selecting unit that selects any one or both of an appropriate document tilt detection method and an appropriate document position detection method according to any one or both of the determined type of document and the determined shape of the document; and a document detecting unit that detects any one or both of a tilt of a document and a position of a document by using the selected detection method.