1. A computer implemented method, comprising: providing a database of image index files for generating similarity scores; scanning a webpage for a digital image; calculating an image index file for the digital image from the webpage; comparing the image index file for the digital image from the webpage with at least one image index file stored in the database to generate a similarity score representative of a variable degree of non-matching between the digital image from the webpage and a digital image corresponding to the at least one image index file from the database; and comparing the similarity score to a similarity threshold score to determine whether to filter the digital image from the webpage; wherein the database further comprises a monosemantic descriptor for each image index file, and further comprising calculating a monosemantic descriptor for the digital image from the webpage, and comparing the monosemantic descriptor for the digital image from the webpage with the monosemantic descriptor for each image index file in the database before the comparing of the image index file for the digital image from the webpage with at least one image index file in the database; wherein the calculating of the monosemantic descriptor comprises: dividing the digital image from the webpage into a plurality of cells; calculating an image descriptor for each of the plurality of cells; and aligning the image descriptor for each of the plurality of cells to calculate the monosemantic descriptor.