Patent ID: 9245204
Filing Date: 2016-01-26
CPC Classification: G06K

Claim Text:
1. A method for comparing a first image with a second image, comprising: identifying first keypoints in the first image and second keypoints in the second image; forming matches between the first and second keypoints by associating each first keypoint with a corresponding second keypoint; calculating a plurality of first distance ratios, each first distance ratio being based on the ratio of the distance between a pair of said first keypoints and the distance between a corresponding pair of said second keypoints matching the pair of first keypoints; arranging a distribution of values of said calculated plurality of first distance ratios in a histogram having a plurality of ordered bins each corresponding to a respective interval of values of the first distance ratios, the histogram enumerating for each bin a corresponding number of first distance ratios of the distribution having values comprised within the respective interval; generating an outlier density function expressing a statistical distribution of a plurality of second distance ratios corresponding to a random selection of keypoints pairs in the first and second images, said plurality of second distance ratios being based on the ratio of the distance between pairs of first keypoints in the first image and the distance between corresponding pairs of randomly selected second keypoints in the second image; discretizing said outlier density function by generating for each of said bin a corresponding outlier probability density value; determining a number of correct keypoint matches, each formed by a first and a second keypoint corresponding to a same point of a same object depicted in the first and second images, said determining a number of correct keypoint matches including: wherein for comparing said first image with said second image the determined number of correct keypoint matches is exploited.