Image synthesis system, image synthesis device therefor, and image synthesis method

The present invention determines a projection condition according to the position of a detected attention object when a virtual space is formed and an image is projected to thereby improve how the image looks. An image display system performs image conversion processing on images from cameras mounted in a vehicle and displays the images, and is provided with: a plurality of cameras; a detection unit which detects an attention object around the vehicle on the basis of information acquired via the plurality of cameras, any other sensor, or a network, or the like; a deformation/synthesis unit which deforms and synthesizes the images captured by the plurality of cameras using the shape of a virtual projection plane, a virtual point of view, and a synthesis method, which are determined according to positional information of the attention object detected by the detection unit; and a display unit which displays the images deformed and synthesized by the deformation/synthesis unit.