Re: IDLanROI Confusion

["Mark Hadfield" <m.hadfield(at)niwa.cri.nz>]

"Craig Markwardt" <craigmnet@cow.physics.wisc.edu> wrote in message
onitkkcp6b.fsf@cow.physics.wisc.edu">news:onitkkcp6b.fsf@cow.physics.wisc.edu...
>
> More than likely the region of interest becomes pixelated into square
> pixels.  It's pretty clear to me that this will give a greater
> perimeter than a true circle since there are more horizontal and
> vertical segments than are required.
>
> What happens if you make the circle much much bigger?  I think then
> the answers will converge to what you expect.

I don't.

Consider a pixelated diagonal line segment. The length along the pixel edges
will exceed the true (along-diagonal) length by sqrt(2), however fine you
pixelate it.

---
Mark Hadfield
m.hadfield@niwa.cri.nz  http://katipo.niwa.cri.nz/~hadfield
National Institute for Water and Atmospheric Research