1. An image filing method for storing image data read out from a document in a file as an image file and also retrieving a desired image file from stored image files for output, the method comprising the steps of: in a case where the image file is to be registered for storage: reading out image data from a first document, extracting layout features of the first document from said read-out image data, and generating an image file with said layout features correlated to said read-out image data, said layout features of the first document indicating geometrical properties of elements within the first document; and in a case where the desired image file is to be retrieved for output: reading out image data from a second document, extracting layout features of the second document from said read-out image data, and retrieving any of the stored image files having registered layout features corresponding to said layout features of the second document as the desired image file, said layout features of the second document indicating geometrical properties of elements within the second document.