comp.lang.idl-pvwave archive: archive » Re: intersecting polygons

Home » Public Forums » archive » Re: intersecting polygons

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: intersecting polygons [message #29393 is a reply to message #29386]

Sun, 17 February 2002 17:38

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Jonathan Pearce (jvp10@psu.edu) writes:

> Does anybody know of, or have a routine that could take polygonal
> areas and find the common area between them? Consider the first
> polygon defined by the set of points x1,y1 where x1 and y1 are arrays.
> The second polygon is defined by the set of points x2 and y2. What I
> am looking for is the points where the lines given by x1,y1 and x2,y2
> intersect. Owing to limited time I am wondering if anybody has written
> such a routine, that would return a polygon describing the area common
> to both polygons.

This probably falls under the category of the world's
biggest hack, but I've used it to good effect.

I use POLYFILLV with the two polygons to get a list
of indices (or pixels) that belong to the two polygons.
I then find the intersection of the two sets of pixels
with the SetIntersection program (modified with some
error checking in my real-world program), that you can
find here:

http://www.dfanning.com/tips/set_operations.html

Knowing the pixel "size" allows me to calculate
areas, etc. You can probably use IDLanROI for the
same purpose. It's worked for me, although I don't
make any claims as to its elegance. :-)

Cheers,

David

--
David W. Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

Report message to a moderator

[Message index]

		Re: intersecting polygons By: meron on Mon, 18 February 2002 15:45
		Re: intersecting polygons By: Pavel A. Romashkin on Mon, 18 February 2002 14:40
		Re: intersecting polygons By: jvp10 on Mon, 18 February 2002 04:03
		Re: intersecting polygons By: David Fanning on Sun, 17 February 2002 17:38

Previous Topic:	Re: debug IDL DLM in Visual C++
Next Topic:	color and idl -rt

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Thu Oct 16 01:27:32 PDT 2025

Total time taken to generate the page: 1.20121 seconds