1. An image processing apparatus comprising: an additional-object registration unit that refers to an image read from a setting form, the setting form including (a) an additional-object specification field used by a user to present an additional object that is placed onto a document in order to specify an extract area to be extracted from an image read from the document, and (b) a processing specification field used by the user to specify processing to be performed on information obtained from the extract area, identifies an image of the additional object presented in the additional-object specification field and processing specified in processing specification field on the read image of the setting form, establishes an association between the image of the additional object and the processing, and registers the image of the additional object and the processing associated therewith; and a read-image processing unit that searches the read image of the document for the image of the additional object and performs the processing associated with the image of the additional object on the information obtained from the extract area specified by the image of the additional object.