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Re: IDL Average Value Graphs [message #61506 is a reply to message #61413]

Thu, 17 July 2008 12:09

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

andybohn@gmail.com writes:

> When I ran POLYFILLV on a triangle, it returned just a 1d array of all
> the pixels in the triangle. I just wish it had an argument that
> returns a 2d array (the x and y coordinates of all of the pixels in
> the polygon). It's simple to convert back, but it's just a little
> inconvenient. Not a big deal.

I am still not understanding why you have to convert
anything. These are the indices of the image that are
inside the triangle. Why can't you use them directly?

I *believe* (although I am not 100% certain about this)
that a pixel is considered "inside" the polygon if the
lower-left corner of the pixel is inside. I don't recall
the details now, but I do know there is a difference
between POLYFILLV and what, for example, comes back
from IDLanROI, which I think uses the center of the pixel.

This goes back too many years. I may have made a note
about this in my FIND_BOUNDARY program, because it came
up when I was working on that project.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming (www.dfanning.com)
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		IDL Average Value Graphs By: andybohn on Tue, 15 July 2008 13:51
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 08:33
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 10:55
		Re: IDL Average Value Graphs By: Jeremy Bailin on Wed, 16 July 2008 11:18
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 18:11
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 16:02
		Re: IDL Average Value Graphs By: Jean H. on Fri, 18 July 2008 10:20
		Re: IDL Average Value Graphs By: Jean H. on Thu, 17 July 2008 14:52
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 12:09
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 11:02

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