1. An image processor for receiving camera images taken with a plurality of cameras capturing the surroundings of a vehicle and generating a synthesized image from the camera images, the image processor comprising: a parameter generation section constructed to be able to generate a plurality of image synthesis parameter groups each representing the correspondence between the camera images and the synthesized image and having different spatial or temporal resolution relations, wherein the synthesized image is generated from the camera images according to the image synthesis parameter group generated by the parameter generation section, and the parameter generation section switches the image synthesis parameter group to be generated according to an output of a vehicle motion detection section for detecting the motion of the vehicle.