[Insight-users] applying the transformation matrix

[Romain Lebel]

I'm sure i'm appling hte right matrix because my images are nearly mapped
it's just that my scaling is not centred on the mass center

how should i take the center in account when applying the matrix?
Miller, James V (Research) a écrit :

>The matrix computed maps from the fixed image's coordinate space to the moving image's coordinate space. As such, if you take a position in the fixed image and apply the transformation, you will have the corresponding position in the moving image.
> 
>It sounds like you are attempting to do the opposite, which requires either the inverse transform or swapping the fixed and moving images.
> 
>Jim
>
>	-----Original Message----- 
>	From: insight-users-bounces+millerjv=crd.ge.com at itk.org on behalf of Romain Lebel 
>	Sent: Tue 12/14/2004 6:22 AM 
>	To: insight-users at itk.org 
>	Cc: 
>	Subject: [Insight-users] applying the transformation matrix
>	
>	
>
>	Hi every one!
>	
>	I'm using the itk affine transform to get my images registred.
>	The thing is that i need to use the matrix outputed by itk (for
>	interfacing with another part of a software).
>	
>	If i undderstood well the matrix outputed is the one that put the moving
>	image in the physical space of the fixed image (no need to use the
>	invers transform).
>	
>	When i apply directly this matrix to the moving image i do not recover
>	exactly the registred image ouputed by itk. What i do is take a point in
>	the moving image. Compute it's coordinate in the fixed image using the
>	matrix. And then get the gray level of the corresponding nearest
>	neighboor in the moving image ( i tried linear interpolation and get
>	same results so i don't think it is a problem of interpolation)
>	
>	I tried with wery simple synthesis images (white pad on black
>	background). If there is only a translation beetween the image  i manage
>	to recover the right image. When there is only scaling i find the right
>	scaled image but my center is at the wrong place (no on the center of
>	mass outputed by itk)
>	
>	my question is how to apply the transformation matrix to get the same
>	image as the one outputed by itk using resample filter?
>	
>	ps: sorry for this long mail but i tried to describe as pricisely as
>	possible
>	
>	--
>	Romain Lebel
>	PhaseView - Telecom Paris
>	37-39 rue Dareau, 75014 Paris
>	Tel : +33 (0)1 45 81 81 68     Fax: +33 (0)1 45 81 81 44
>	Internet :  www.phaseview.fr
>	
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>
>  
>


-- 
Romain Lebel
PhaseView - Telecom Paris
37-39 rue Dareau, 75014 Paris
Tel : +33 (0)1 45 81 81 68     Fax: +33 (0)1 45 81 81 44
Internet :  www.phaseview.fr