This invention provides methods, apparatus and article of manufacture used as
a countermeasure to image distorting. The present invention involves automatically
detecting the presence of distortion in a presumed distorted image, measuring the
magnitude and type of distortion, and finally creating a realigned image. Once
image distortion is removed, conventional invisible watermark extraction methods
are employed to extract the watermark from the realigned image. The automatic method
does not depend on a process of visually examining a composite image and recording
the coordinates of pixel locations closest to common image features in a distorted
image and reference image. Generally, the presumed distorted image is resized to
the same size as the reference image. Reference centers at at least three distinct
points that do not form a straight line are selected. At each reference center,
a sub-image is excised. Pairs of sub-images, one excised from the reference image
and the other excised from the distorted image, having the same reference center
are used in the process of removal of the distortion.
