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Re: Average outline of several contours [message #37114 is a reply to message #37021]

Fri, 21 November 2003 07:14

K. Bowman
Messages: 330
Registered: May 2000

Senior Member

In article <f40e34db.0311202122.37499b6@posting.google.com>,
Beat.Schmutz@flinders.edu.au (Beat Schmutz) wrote:

> I have combined 8 contours of bone cross-sections into one image
> (individual ROIs in a IDLgrROIGroup). Now I like to determine the
> path/outline which represents the average of these 8 contours. Is
> anyone aware of a program/code/method that enables me to achieve this?
> Any help would be greatly appreciated.
>
> Beat Schmutz

Assuming the contours are roughly circular, you could do this:

Compute the centroid (average position) of all the points in all the
contours.

Transform the contours to polar coordinates centered on the centroid.

Interpolate each contour to regularly spaced points in theta.

Average the radial values of the contours at each regular theta.

Transform back to Cartesion coordinates, if necessary.

The only tricky thing I see is doing the interpolation in theta across
the "seam" (where theta equals both 0 and 2 pi). That should be easy to
fix by rotating the coordinates by pi for points near the seam.

Ken Bowman

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[Message index]

		Average outline of several contours By: Beat.Schmutz on Thu, 20 November 2003 21:22
		Re: Average outline of several contours By: Beat.Schmutz on Mon, 24 November 2003 19:44
		Re: Average outline of several contours By: Craig Markwardt on Sun, 23 November 2003 12:19
		Re: Average outline of several contours By: Beat.Schmutz on Sun, 23 November 2003 03:42
		Re: Average outline of several contours By: K. Bowman on Fri, 21 November 2003 07:14

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