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Routine to return indices for circle in R2 [message #9931]

Mon, 08 September 1997 00:00

David Foster
Messages: 341
Registered: January 1996

Senior Member

Has someone written, seen or heard of a routine that will return
the indices of a circle within an image of given dimensions,
given the radius and center coordinate of the circle? I vaguely
remember seeing this in a newsgroup post some time ago.

For an image of size NX x NY, with the circle at coordinate (Cx,Cy)
and radius R, I came up with:

indices = lindgen(long(NX)*NY)
yc = indices / NY
xc = indices - (yc * NY)
circle = where( sqrt( (xc - Cx)^2 + (yc-Cy)^2 ) le R )

Can anyone suggest a method that is (a) faster, (b) more clever,
(c) more elegant, or (d) uses less memory. I'd be willing to settle
for just one of the above!

Thanks!

Dave
--

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~
David S. Foster Univ. of California, San Diego
Programmer/Analyst Brain Image Analysis Laboratory
foster@bial1.ucsd.edu Department of Psychiatry
(619) 622-5892 8950 Via La Jolla Drive, Suite 2240
La Jolla, CA 92037
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~

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Routine to return indices for circle in R2

By: David Foster on Mon, 08 September 1997 00:00

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