1. A composite image-generating device comprising: a geometric transformation table that assigns coordinates corresponding to positions of pixels of an output image on an input image received from a capturing section; and an output image-generating section that generates the output image by performing interpolation using pixel values of pixels of the input image that surround a point that corresponds with the coordinates assigned on the input image in the geometric transformation table, wherein the output image-generating section generates the output image by replacing, based on overlay data, at least part of the pixel values of the pixels that surround the point that corresponds with the coordinates assigned on the input image and then performing the interpolation, with regard to the pixel of the output image for which the overlay data is provided, the geometric transformation table includes a selection flag that corresponds to the positions of the pixels of the output image, and the selection flag indicates which of the pixels of the output image are replaced by the output image-generating section based on the overlay data.