1. An image-capturing apparatus comprising: an image-capturing unit having a plurality of pixels disposed two-dimensionally; an adding unit that generates an image by adding outputs of pixels present around a given pixel at the image-capturing unit to an output of the given pixel; an image processing unit that processes the image resulting from addition executed by the adding unit; and an addition pattern generating unit that generates an addition pattern with which pixel outputs are added together by the adding unit in correspondence to a type of image processing to be executed by the image processing unit.