1. An image processing determining apparatus comprising: an external device outputting display data including an image; an edge extractor configured to extract a plurality of edges indicating the outline of an object in the image included in the display data output from the external device with lines; an edge selector, configured to select certain edges from the plurality of edges extracted by the edge extractor, by a certain selection method; an edge image generator, configured to generate an edge image composed of the certain edges selected by the edge selector; and a display apparatus displaying the edge image generated by the edge image generator, wherein the edge selector selects the certain edges by the selection method matched with characteristics of the external device, wherein the display apparatus includes a heads-up display that performs displaying on a front window of a vehicle and another display device, and wherein the edge selector sets an amount of the certain edges selected for display in the heads-up display so as to be smaller than an amount of the certain edges selected for display in the another display device.