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 synthesized image having a plurality of areas each including at least one pixel and each camera image having a plurality of areas each including at least one pixel, the image processor comprising: a parameter storage section for storing a plurality of sets of an image synthesis parameter group, each image synthesis parameter group representing a correspondence between any of the areas of the camera images and any one of the areas of the synthesized image, and a filter parameter group corresponding to each image synthesis parameter group, each filter parameter group having a plurality of filter parameters and each filter parameter having a correspondence with an area of the camera images; a parameter selection section for selecting at least one among the plurality of sets of the image synthesis parameter group and the corresponding filter parameter group stored by the parameter storage section according to a motion of the vehicle detected by a vehicle motion detection section and an output of a vehicle status detection section for detecting the status of the vehicle such as an operation by a driver of the vehicle or whether or not an obstacle exists in the surroundings of the vehicle; and a filtering section for performing frequency band limitation filtering of the camera images according to the filter parameter group of the set selected by the parameter selection section, wherein the synthesized image is generated from the camera images filtered by the filtering section according to the image synthesis parameter group of the set selected by the parameter selection section to generate the synthesized image with optimal quality to reduce aliasing distortion.