1. An image processing apparatus configured to be used on a vehicle, the image processing apparatus comprising: (a) an image processor configured to: (i) generate a surrounding image showing a surrounding region of the vehicle viewed from a virtual viewpoint located in the vehicle, by using an image captured by a camera mounted on the vehicle; (ii) obtain a vehicle image that is divided into plural portions showing the vehicle viewed from the virtual viewpoint; (iii) generate a combined image by combining the surrounding image and the vehicle image having the plural portions; and (iv) output the combined image for display on a display apparatus, and (b) a controller configured to determine a transparency percentage of each of the plural portions of the vehicle image, wherein the image processor causes the plural portions to be semi-transparent or to be transparent at the determined transparency percentages such that the combined image includes the surrounding image and the vehicle image having the plural portions caused to be semi-transparent or to be transparent at the determined transparency percentages, wherein the plural portions include parts that are of a cabin of the vehicle and are physically independent of one another, wherein a list of the parts of which the transparency percentages are settable is displayed on a transparency percentage setting screen, wherein a user enters an arbitrary transparency percentage for each of the parts to the transparency setting screen, wherein the parts that are physically independent of each other are each individually selectable and the transparency percentage setting screen includes a list of the plural portions each individually selectable, and wherein the controller is further configured to perform at least one of: as a speed of the vehicle becomes higher, increasing the transparency percentage of a portion corresponding to a higher portion of the vehicle, among the plural portions and as a speed of the vehicle becomes lower, increasing the transparency percentage of a portion corresponding to a lower portion of the vehicle, among the plural portions.