Posted by
Per Christian Henden on
Dec 06, 2007; 10:56pm
URL: http://imagej.273.s1.nabble.com/Plugin-announcement-Orientation-measurements-tp3697674p3697685.html
On Thursday 06 December 2007 01:00:41 Albert Cardona wrote:
> Hi Per,
>
> Would you comment on how is your orientation finder different than SIFT
> (Scale Invariant Feature Transform) by D. Lowe 2004 ?
I assumed you mean this article
http://www.cs.ubc.ca/~lowe/papers/ijcv04.pdfI've just read the orientation part. SIFT looks like a smart approach, thanks
for pointing me to it. It solves a different problem from my plugin, though.
SIFT finds a number of 'keypoints' in the image. These keypoints are
considered characteristic to the image. One of the attributes of a keypoint
is its orientation. The orientation is determined by an equation using four
neighbouring points to the keypoint in a scaled version of the image. There
is no concept of the orientation of an object, only orientation of keypoints,
althout it would probably be possible to aggregate these keypoint orientations
in some way.
My plugin assumes a segmented image/volume, so that each object you want to
measure the orientation of has its own label. For each object it looks at the
coordinates of the points that the object consists of and builds a covariance
matrix from those. The covariance matrix is used for calculating a vector
describing the direction of the object.
I hope that was a helpful answer.
Let me know if there are more questions!
PER