1. An image similarity determining device for determining similarity between an input image and a data source image, the image similarity determining device comprising: a memory to store instructions; and a processor configured to execute the stored instructions to perform an operation, the operation including: dividing the input image into at least one input image region and dividing the data source image into at least one image region to be matched, and extracting feature points of each input image region and each image region to be matched; determining, with respect to each input image region, one to one matched feature point pairs between the input image region and each image region to be matched, according to feature similarities between each feature point of the input image region and each feature point of respective image regions to be matched, and forming a matched feature point set including all the matched feature points for the input image region and corresponding image regions to be matched according to the one to one matched feature point pairs; determining, with respect to each input image region and a corresponding image region to be matched, a geometry similarity between the input image region and the corresponding image region to be matched, based on the distribution of respective feature points in the matched feature point set of the input image region and the distribution of respective feature points in the matched feature point set of the corresponding image region to be matched; and determining the image similarity between each input image region and a corresponding image region to be matched, according to the geometry similarity between the input image region and the corresponding image region to be matched, and determining the similarity between the input image and the data source image according to the image similarities between each of the input image regions of the input image region and respective corresponding image regions to be matched.