1. An image output apparatus comprising: a receiving section for receiving, from a portable terminal apparatus including an image capture section, captured image data that is captured by the image capture section; an edge information obtaining section for obtaining edge information indicative of where an edge pixel group, which is a group of edge pixels connected to each other in a form of a line segment and which is detected in a captured image of the captured image data, is positioned on the captured image; an edge extraction processing section (i) for determining as an extraction region either (a) a quadrangular region enclosed by a quadrangle in which all internal angles are less than 180° and sides are constituted by 4 edge pixel groups each in the form of a line segment, the 4 edge pixel groups being indicated by the edge information, or (b) a polygonal region enclosed by a polygon in which all internal angles are less than 180° and sides are constituted by at least one edge pixel group in the form of a line segment, which edge pixel group is indicated by the edge information, and at least one line segment located on an end portion of the captured image, and (ii) for cutting out, as output target image data, image data of the extraction region from the captured image data; and an output section for outputting the output target image data or an image of the output target image data.