To provide an image reader which reduces a time for reading operation and analysis processing and precisely obtaining document area information, and to provide a control method for the image reader.

The image reader detects image data parts of high resolution for two sides of a document and uses image data parts of high resolution not for four sides but two sides of the document to detect a contour of an image, and a read image is cut out in a range of the detected contour of the image. The image reader uses image data parts of high resolution for two sides to detect an inclination of the document.