[Insight-developers] Fwd: Documentation on Spacing and Orientation.

[Matthew McCormick (thewtex)]

---------- Forwarded message ----------
From: Matthew McCormick (thewtex) <matt at mmmccormick.com>
Date: Mon, Jan 24, 2011 at 5:38 PM
Subject: Re: [Insight-developers] Documentation on Spacing and Orientation.
To: "Williams, Norman K" <norman-k-williams at uiowa.edu>


Hi Norman,

On Mon, Jan 24, 2011 at 9:34 AM, Williams, Norman K
<norman-k-williams at uiowa.edu> wrote:
> This came up in some work I was doing last week, which was causing me some
> confusion.
>
> Namely, the Origin of an image is a point in physical space, corresponding
> to the voxel at index (0,0,[0,0,...]).
>

Yes.

> This was confusing me because if I need to use an individual component of
> the origin to do something (unavoidably) in Index space, I needed to know
> the mapping of XYZ to IJK as it were, which is dependent on the voxel
> organization, which is dependent on the direction cosines.
>

This can be performed with ImageBase::TransformIndexToPhysicalPoint

> So, a similar issue arises with Image Spacing.  Reading the source code,
> I'm confused whether the spacing is in Index or Physical space.  Which is
> it?

Physical space.

HTH,
Matt