[MINC-users] Register and Display: internal representation?

[Christopher Bailey]

Dear Jason,

Thank you for you reply; print_world_value gives correct values.

Do you know if postf behaves the same as register & Display? I don't 
have easy access to an IRIX... I suppose if one extracts a TAC using a VOI in
postf, the underlying code uses the original file values instead of what 
postf shows on the screen.

Thank you for your help,

-Chris

On Fri, 25 Jun 2004, Jason Lerch wrote:

> The ranges matter in conjunction with the data type. register and 
> Display always open files as byte, so if the files are stored in a 
> different format, then this could be your answer. You can always create 
> a little mask of the voxels that you are interested in and use 
> mincstats to figure out the real values there. I think the command 
> print_world_value uses the volume's data-type as well.
> 
> Cheers,
> 
> Jason
> 
> On Jun 25, 2004, at 9:10 AM, Christopher Bailey wrote:
> 
> >
> > Dear MINC-users,
> >
> > I want to subtract one 3D (frame) from another:
> >
> > newframe = frame1 - frame0
> >
> > I use mincmath as follows (correct?):
> >
> > mincmath -sub frame1 frame0 newframe
> >
> > Both frames are signed floats with slightly different ranges (0->2e5 
> > and
> > 0->2e6) and are coregistered. They both contain lots of zeros at the 
> > edges
> > of the image. When I open "newframe" in either register or Display, 
> > those
> > same voxels that should still be zero, now have a mysterious value of
> > -185.253! Doing the subtraction the other way round yields +185.253.
> >
> > I opened "newframe" in AFNI, which DID show zeros in the edge voxels! I
> > also did a mnc2ana on the file and looked at it in mricro---again zeros
> > on the edges as it should be.
> >
> > So what is going on with register and Display? We have concluded it 
> > must
> > be an internal representation issue, but I would still like comments on
> > this. I'm of course concerned about doing further analysis on these
> > files---I want zero to be zero!
> >
> > All the best,
> >
> > Chris Bailey
> > Center for Functionally Integrative Neuroscience
> > Aarhus General Hospital, Denmark
> >
> >
> >
> > _______________________________________________
> > MINC-users@bic.mni.mcgill.ca
> > http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
> 
>