1. A computer-implemented method comprising: maintaining an index of image index files, each image index file being representative of a digital image of an advertisement and inclusive of a plurality of image metrics for multiple regions of the digital image of the advertisement; receiving an image query, the image query comprising a digital image; calculating an image index file representative of the digital image of the image query and inclusive of a plurality of image metrics for multiple regions of the digital image of the image query; comparing the image index file inclusive of a plurality of image metrics for multiple regions of the digital image of the image query with the image index files, which are representative of the digital images of the advertisements and inclusive of a plurality of image metrics for multiple regions of the digital images of the advertisements; transmitting at least one advertisement based on the comparison.