There has been proposed an image reading apparatus including a read unit below read glass for executing read operation through the read unit while conveying the read unit below the read glass so as to read a document placed on the read glass and generate image data representing a read image of the document. 
If the image reading apparatus has a copy function, the generated image data is supplied to print processing, for example.  That is, the image data representing the read image is supplied to print processing, whereby a copy image of the read document is printed on a record sheet of paper.  As for such an image reading apparatus having the copy function, there has been proposed a digital multi-function device having a printer function, a fax function, etc.,  as well as the copy function. 
Further, there has also been proposed an image reading apparatus for keeping track of an area where a document is placed on read glass by prescanning and then at the scanning time, limiting the read area to the area where the document is placed rather than the whole area below the read glass and conveying a read unit in the read area for reading the document. 
In addition, there has been proposed an image reading apparatus for detecting the size of a document tabled on the read result of the document through a read unit.  For example, an image reading apparatus for detecting an edge of a document from the read result and detecting the document size from the detection result has been proposed (refer to JP-A-2004-201240, JP-A-2005-285010, JP-A-7-245681, and JP-A-2001-036696). 
The detection result of the document size obtained in such a manner is used, for example, for the automatic setting operation of a read area at the scanning time and the automatic setting operation of a scaling factor at the copy time.  For example, the scaling factor is set conforming to the ratio between the document size and the record sheet size from the detected document size and the record sheet size, the read image is scaled up or down conforming to the setup scaling factor, and a copy image of the document is printed on the record sheet at the scaling factor suited to the sheet size. 
In addition, there has been proposed an image reading apparatus for detecting the size and the inclination of a document tabled on the read result of the document through a read unit (refer to JP-A-11-252351, JP-A-2007-082047, and JP-A-2007-088654).  An image reading apparatus using the detection result of the size and the inclination of a document for the automatic setting operation of a read area at the scanning time and the automatic setting operation of a scaling factor and the inclination correction operation at the copying time has also been proposed. 
For example, the scaling factor is set conforming to the ratio between the document size and the record sheet size from the detected document size and the record sheet size, the rotation amount is set from the inclination of the document, the image data as the read result is rotated for correcting the inclination and is scaled up or down conforming to the setup scaling factor, and the image of the read document is printed on the record sheet at the scaling factor matched with the record sheet size.