A method for detecting a geometrically transformed copy of content in at
least a portion of an image, comprises the steps of: (a) providing first
and second digital images; (b) searching for objects of interest within
each digital image; (c) identifying pairs of corresponding objects of
interest in the digital images, wherein each pair of corresponding
objects of interest comprises a located object of interest in the first
digital image and a corresponding located object of interest in the
second digital image that corresponds to the located object of interest
in the first image; (d) locating feature points on each located object of
interest in each digital image; (e) matching feature points on the
located object of interest in the first digital image to the feature
points on the corresponding object of interest in the second digital
image, thereby generating a set of correspondence points for each image;
(f) determining parameters of a geometric transformation that maps the
set of correspondence points in the first digital image into the set of
correspondence points in the second digital image; (g) transforming the
first digital image according to the parameters of the geometric
transformation determined in step (f); and (h) detecting regions of
similarity between the content of the transformed first digital image and
the second digital image, thereby determining if the second image
contains a region that is a geometrically transformed copy of a region in
the first image.