[Insight-developers] Image Orientation

[Ross Whitaker]

Yo,



>   > Can we add the ability to specify image orientation to our base image
>   > class?  Dicom specifies orientation via a set of three vectors
>   > indicating x, y, and z directions in physical space - or we could pass a
>   > vnl_matrix to the image class.   It would be part of the existing image
>   > index to physical space transform.
>
>   If we decide to add this to the image class (a proposition on which
>   I'm still neutral), the right way would be to replace the current
>   origin and spacing with an AffineTransform object, which contains all
>   the desired information (including the inverse transform).  This would
>   require changes to the classes which currently use the origin and
>   spacing to determine the physical coordinates.  If we want to save a
>   little space, we could use a pointer to the AffineTransform; if the
>   pointer is zero, then an identity transform is assumed.  (But this
>   might cause more problems than it's worth.)
>



If we do this, there should be a way to bypass this and get regular (fast)
pixel access without having to go through the transform object.

An (attractive) alternative is to agree that in *most* cases we access pixels
on the cardinal grid and for those filters that *need* absolute, 3D (ND :} )
position, the passes in a corresponding transform.  That's how we do it in
our current toolkit.  So the output of the Dicom reader would not only be a
volume, but *also* other information such as transforms, text, whatever, not
all intimately tied to the image object.

My preference is the later.  I.e. we stick to the basic, simple definition of
the image object and *not* try to make it fit every particular situation.

Cheers,

Ross


Paul Hughett wrote:

> Steve Aylward:
>
> > We need to maintain MR orientation info on one of our apps.
>
>
> Paul Hughett
>
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--
Ross T. Whitaker, Assistant Professor
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University of Utah
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