1. An image processing apparatus comprising: a three-dimensional model storage unit configured to store a three-dimensional model data expressing a three-dimensional model of a three-dimensional region, positions of a plurality of devices including a camera disposed in the three-dimensional region as positions in the three-dimensional model, and a plurality of device icons expressing types of the devices in the three-dimensional model; an acquiring unit read from a non-transitory recording medium and implemented by a processor configured to acquire a shot image taken at the camera and a shooting direction when shooting; a composing unit read from the non-transitory recording medium and implemented by the processor configured to determine a view point with respect to the three-dimensional model as the camera position disposed in the three-dimension region, generate a three-dimensional model by disposing the device icons corresponding to the device types on positions of the devices stored in the three-dimensional model storing unit according to the determined view point and the shooting direction, generate a two-dimensional projection image that the three-dimensional model is projected from a same direction as the shooting direction, at a same scaling factor as a scaling factor of the shot image, onto a two-dimensional plane, and generate a composite image by composing the shot image in a predetermined region that is generated so as to match a center position of the generated two-dimensional projection image with a center position of said shot image, on the generated two-dimensional projection image; and an output unit read from the non-transitory recording medium and implemented by the processor configured to output the composite image, wherein the composing unit is configured to display, in case that said device icon is displayed overlapping with the predetermined region when the device icon not corresponding to the camera is displayed on the composite image, the predetermined region in the foreground rather than said device icon.