1. An image processing system with an image conversion processor that composites overhead view images obtained by converting viewpoints of photographed images of a plurality of cameras, comprising: an image detection processor that extracts image feature amounts from the photographed images, wherein the image conversion processor performs composition by blending the overhead view images corresponding to a superposition area which are parts of the overhead view images generated from the photographed images of two of the plurality of cameras, at blend rates set in accordance with intensities of a correlation between the image feature amounts of the photographed images extracted by the image detection processor, in the superposition area that is photographed by the two cameras overlappingly.