Comments on: Spatial transformations: Affine http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/ 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/2006/02/07/spatial-transformations-affine/#comment-24479 Steve Wed, 14 Sep 2011 16:11:41 +0000 http://blogs.mathworks.com/steve/?p=35#comment-24479 Tim—That expression would apply a rotation with R, followed by a scaling with S, followed by a translation with T. Tim—That expression would apply a rotation with R, followed by a scaling with S, followed by a translation with T.

]]> By: Tim http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-24471 Tim Sat, 10 Sep 2011 20:45:17 +0000 http://blogs.mathworks.com/steve/?p=35#comment-24471 Hi Steve, I'm one of those people that's used to the other form of transformation notation and would like to make sure I'm using the one you show correctly. If I want to do a composite transformation of a rotation-scaling-translation transformation using the 3x3 affine transformation matrices R, S, T for rotation, scaling, and translation, respectively, is the below correct or do I have to 'transpose' the matrix order (or the matrices themselves or something like that? [x',y',1] = [x,y,1]*R*S*T Hi Steve,
I’m one of those people that’s used to the other form of transformation notation and would like to make sure I’m using the one you show correctly. If I want to do a composite transformation of a rotation-scaling-translation transformation using the 3×3 affine transformation matrices R, S, T for rotation, scaling, and translation, respectively, is the below correct or do I have to ‘transpose’ the matrix order (or the matrices themselves or something like that?
[x',y',1] = [x,y,1]*R*S*T

]]> By: Steve http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-23022 Steve Tue, 20 Apr 2010 11:37:04 +0000 http://blogs.mathworks.com/steve/?p=35#comment-23022 Jules—There is no function called <tt>affine</tt> in MATLAB or in the Image Processing Toolbox. Jules—There is no function called affine in MATLAB or in the Image Processing Toolbox.

]]> By: Jules http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-23021 Jules Tue, 20 Apr 2010 09:57:10 +0000 http://blogs.mathworks.com/steve/?p=35#comment-23021 I am trying to use the affine function and it is giving me the error ??? Error using ==> mtimes Integers can only be combined with integers of the same class, or scalar doubles. Error in ==> affine at 154 XYZmm = old_R*(XYZvox-1) + repmat(old_T, [1, 8]); so I changed my tranformation matrix into type double and now it is tranforming my original 3D image into a 2D image with and thie warning comes up Warning: Matrix is singular to working precision. In affine at 231 I'm not quite sure what is going on here. Any help would be great, thanks! I am trying to use the affine function and it is giving me the error

??? Error using ==> mtimes
Integers can only be combined with integers of the same class, or scalar doubles.

Error in ==> affine at 154
XYZmm = old_R*(XYZvox-1) + repmat(old_T, [1, 8]);

so I changed my tranformation matrix into type double and now it is tranforming my original 3D image into a 2D image with and thie warning comes up

Warning: Matrix is singular to working precision.
In affine at 231

I’m not quite sure what is going on here. Any help would be great, thanks!

]]> By: Steve http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-21200 Steve Wed, 29 Oct 2008 23:02:48 +0000 http://blogs.mathworks.com/steve/?p=35#comment-21200 Maher—You might try using <tt>cpselect</tt> to select pairs of corresponding points, followed by <tt>cp2tform</tt> to infer an affine transformation. Maher—You might try using cpselect to select pairs of corresponding points, followed by cp2tform to infer an affine transformation.

]]> By: Maher http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-21184 Maher Mon, 27 Oct 2008 09:44:27 +0000 http://blogs.mathworks.com/steve/?p=35#comment-21184 Dear Steve, I am trying to find the similarity degree between historic and modern maps (statistically). I need to convert the coordinates of the modern image to fit that of the old one using Matlab.For example: through affine transformation. Please, advise so. Great Thanks for you. Dear Steve,
I am trying to find the similarity degree between historic and modern maps (statistically). I need to convert the coordinates of the modern image to fit that of the old one using Matlab.For example: through affine transformation.
Please, advise so.
Great Thanks for you.

]]> By: Steve http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-12255 Steve Fri, 19 Oct 2007 11:46:16 +0000 http://blogs.mathworks.com/steve/?p=35#comment-12255 Eric—What do you mean? Eric—What do you mean?

]]> By: Eric Monse http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-12245 Eric Monse Fri, 19 Oct 2007 09:45:09 +0000 http://blogs.mathworks.com/steve/?p=35#comment-12245 Can't wait to see Matlab. Can’t wait to see Matlab.

]]> By: Steve http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-6735 Steve Wed, 30 May 2007 12:21:14 +0000 http://blogs.mathworks.com/steve/?p=35#comment-6735 Gleb - I'm glad it worked! Gleb – I’m glad it worked!

]]> By: Gleb http://blogs.mathworks.com/steve/2006/02/07/spatial-transformations-affine/#comment-6734 Gleb Tue, 29 May 2007 22:27:27 +0000 http://blogs.mathworks.com/steve/?p=35#comment-6734 Steve, it's exactly what I needed! Thank you again!!! Steve,
it’s exactly what I needed! Thank you again!!!

]]>