his is transformed into an image ellipse
by $(A,T)$.</p>

<p>In term of extent, the normalised patch domain is a square box
centered at the origin, whereas the image domain uses the standard
MATLAB convention and starts at (1,1). The Y axis points downward and
the X axis to the right. These notions are important in the
computation of normalised patches and descriptors
(see <a shape="rect" href="%pathto:tut.covdet.descr">later</a>).</p>

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