Short Listing Likely Images Using Proposed Modified-sift Together with Conventional Sift for Quick Sketch to Photo Matching

The paper proposes the modified-SIFT algorithm which will be a modified form of the scale invariant feature transform. The modification consists of considering successive groups of 8 rows of pixel, along the height of the image. These are used to construct 8 bin histograms for magnitude as well as orientation individually. As a result the number of feature descriptors is significantly less (95%) than the standard SIFT approach. Fewer feature descriptor leads to reduced accuracy. This reduction in accuracy is quite drastic when searching for a single (RANK1) image match; however accuracy improves if a band of likely (say tolerance of 10%) images is to be returned. The paper therefore proposes a two-stage-approach where First Modified-SIFT is used to obtain a shortlisted band of likely images subsequently SIFT is applied within this band to find a perfect match. It may appear that this process is tedious however it provides a significant reduction in search time as compared to applying SIFT on the entire database. The minor reduction in accuracy can be offset by the considerable time gained while searching a large database. The modified-SIFT algorithm when used in conjunction with a face cropping algorithm can also be used to find a match against disguised images.