Comments on: Spatial transformations: Defining and applying custom transforms http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/ Steve Eddins manages the Image & Geospatial development team at The MathWorks and coauthored Digital Image Processing Using MATLAB. He writes here about image processing concepts, algorithm implementations, and MATLAB. Sat, 11 Feb 2012 18:27:50 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Steve http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-24182 Steve Mon, 09 May 2011 14:23:20 +0000 http://blogs.mathworks.com/steve/?p=75#comment-24182 Mary—This post was about defining and applying custom tforms. What information is missing for you? Mary—This post was about defining and applying custom tforms. What information is missing for you?

]]> By: mary http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-24177 mary Sun, 08 May 2011 13:48:12 +0000 http://blogs.mathworks.com/steve/?p=75#comment-24177 Daer Steve, I also have a question for you which is somehow related to the topic of this post: I am trying to implement the global axial bending tranformation for a 3D image along the Y axis. The transformation looks like the following: X=x; Y=-sin(theta)*(z-1/k); Z=cos(theta)*(z-1/k); where theta=k*y (thata changes with y). Besically I would like to applay the transformation [0, -sin(theta),0; 0 cos(theta),0; sin(theta)/k), -cos(theta)/k), 1] to each plane (y,z) of the 3-dimensional image. However, I eperienced that this cannot be done with makatform('afine' but a 'custom' transformaation should be defined. Do you have any idea on how to do it? Daer Steve,
I also have a question for you which is somehow related to the topic of this post:
I am trying to implement the global axial bending tranformation for a 3D image along the Y axis. The transformation looks like the following:
X=x;
Y=-sin(theta)*(z-1/k);
Z=cos(theta)*(z-1/k);

where theta=k*y (thata changes with y). Besically I would like to applay the transformation

[0, -sin(theta),0; 0 cos(theta),0; sin(theta)/k), -cos(theta)/k), 1]

to each plane (y,z) of the 3-dimensional image. However, I eperienced that this cannot be done with

makatform(‘afine’

but a

‘custom’

transformaation should be defined. Do you have any idea on how to do it?

]]> By: Umut http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23532 Umut Sun, 26 Sep 2010 04:57:58 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23532 Steve - this is called: knowledge&experience... it works ,thanks a lot... Steve – this is called: knowledge&experience…
it works ,thanks a lot…

]]> By: Steve http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23530 Steve Sun, 26 Sep 2010 00:13:28 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23530 Umut—Try forming the composite in the opposite order: <pre class="code"> Tc = maketform(’composite’,TT2,TT1); </pre> Umut—Try forming the composite in the opposite order:

Tc = maketform(’composite’,TT2,TT1);
]]> By: Umut http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23529 Umut Sat, 25 Sep 2010 05:17:53 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23529 Hi Steve, I'm confused about using custom transform 3D to 2D. I'm trying to extract an arbitrary single slice from being transformed 3D MR data with 3D-2D tranformation. I have 8 transformation parameters for 3D MR = 3-rotation,3-translation and 2-scale(X,Y). In order to reduce transformation time, I decided to use custom and composite (affine+custom) transform as : TT1 = maketform('affine', T); % T is 4x4 matrix inverseFcn = @(X,t) [X repmat(t.tdata,[size(X,1) 1])]; TT2 = maketform('custom',3,2,[],inverseFcn,30); Tc = maketform('composite',TT1,TT2); R = makeresampler ({'cubic','nearest','nearest'}, 'fill'); TDIMS_A = [1 2 3]; TDIMS_B = [1 2]; TSIZE_B = [round(size(Vol,1)*scx) round(size(Vol,2)*scy)]; TMAP_B = []; F = 0; imT = tformarray(Vol, Tc, R, TDIMS_A, TDIMS_B, TSIZE_B, TMAP_B, F); I get an error : " Error using ==> maketform>composite at 540 Input TFORM objects have inconsistent dimensions." finally, I would be thankful if you could share some suggestions to overcome this inconsistency... Hi Steve,
I’m confused about using custom transform 3D to 2D. I’m trying to extract an arbitrary single slice from being transformed 3D MR data with 3D-2D tranformation. I have 8 transformation parameters for 3D MR = 3-rotation,3-translation and 2-scale(X,Y). In order to reduce transformation time, I decided to use custom and composite (affine+custom) transform as :

TT1 = maketform(‘affine’, T); % T is 4×4 matrix
inverseFcn = @(X,t) [X repmat(t.tdata,[size(X,1) 1])];
TT2 = maketform(‘custom’,3,2,[],inverseFcn,30);
Tc = maketform(‘composite’,TT1,TT2);
R = makeresampler ({‘cubic’,'nearest’,'nearest’}, ‘fill’);
TDIMS_A = [1 2 3];
TDIMS_B = [1 2];
TSIZE_B = [round(size(Vol,1)*scx) round(size(Vol,2)*scy)];
TMAP_B = [];
F = 0;
imT = tformarray(Vol, Tc, R, TDIMS_A, TDIMS_B, TSIZE_B, TMAP_B, F);

I get an error :
“
Error using ==> maketform>composite at 540
Input TFORM objects have inconsistent dimensions.”

finally, I would be thankful if you could share some suggestions to overcome this inconsistency…

]]> By: ftft http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23206 ftft Sun, 20 Jun 2010 08:24:23 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23206 hello i am doing image registration, but when I applied an affine transformation on image, and after applied an inverse transformation the transformed image not returne to original image hello
i am doing image registration, but when I applied an affine transformation on image, and after applied an inverse transformation the transformed image not returne to original image

]]> By: Steve http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23204 Steve Fri, 18 Jun 2010 19:11:07 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23204 RZ—Sure. Rotation and translation are both affine transformations, and the composition of two affine transformations is also affine. So take a T1 matrix that's a rotation matrix, a T2 matrix that's a translation matrix, and multiply them. RZ—Sure. Rotation and translation are both affine transformations, and the composition of two affine transformations is also affine. So take a T1 matrix that’s a rotation matrix, a T2 matrix that’s a translation matrix, and multiply them.

]]> By: RZ http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-23203 RZ Fri, 18 Jun 2010 19:06:19 +0000 http://blogs.mathworks.com/steve/?p=75#comment-23203 Hi Steve, Is there a way to do a transform with only rotation and translation but not scaling? Thanks Hi Steve,

Is there a way to do a transform with only rotation and translation but not scaling?

Thanks

]]> By: Shre http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-22954 Shre Mon, 05 Apr 2010 20:02:43 +0000 http://blogs.mathworks.com/steve/?p=75#comment-22954 Hi Steve, Im working on a facial aging project. I just commented about the same on another post of yours. I realize that this post shows some of those geometrical changes that Im looking out for. so could you please help me out n it. If you check out the before/after photos in the paper (link below) u'll get an idea of what i want....i wanted to avoid using RBF etc..I had to complete this in 3-4 days..Its extremely urgent. Please help! heres the link to the paper im trying to implement http://www.dca.fee.unicamp.br/~leopini/private/pubs/Greyce-2007WesternNYImageProcessingWorksop.pdf Hi Steve,

Im working on a facial aging project. I just commented about the same on another post of yours. I realize that this post shows some of those geometrical changes that Im looking out for. so could you please help me out n it. If you check out the before/after photos in the paper (link below) u’ll get an idea of what i want….i wanted to avoid using RBF etc..I had to complete this in 3-4 days..Its extremely urgent. Please help!

heres the link to the paper im trying to implement

http://www.dca.fee.unicamp.br/~leopini/private/pubs/Greyce-2007WesternNYImageProcessingWorksop.pdf

]]> By: Steve http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/#comment-22233 Steve Mon, 19 Oct 2009 19:27:15 +0000 http://blogs.mathworks.com/steve/?p=75#comment-22233 Douglas—I don't know what you mean by "extract the data point from the deformation grid." Can you be more specific? Douglas—I don’t know what you mean by “extract the data point from the deformation grid.” Can you be more specific?

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