<br>Hi Ramon,<br><br>When you have Anisotropic Scaling and Rotation,<br>that is equivalent to providing Shearing.<br><br>In other words, you can implement Shearing by<br>composing Rotation and Anisotropic scaling.<br><br>Therefore, you cannot have a transform that has<br>
Anisotropic Scaling and Rotation but not Shearing.<br><br>---<br><br>Using the Affine transform sounds like the <br>right thing to do in this case.<br><br><br><br> Regards,<br><br><br> Luis<br><br><br>-----------------------<br>
<div class="gmail_quote">2009/9/5 Ramón Casero Cañas <span dir="ltr"><<a href="mailto:ramon.casero@comlab.ox.ac.uk">ramon.casero@comlab.ox.ac.uk</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">Yang, Jinzhong wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
This is simply an affine transform itk::AffineTransform. <br>
</blockquote>
<br>
<br></div>
Hi Jinzhong,<br>
<br>
Am I wrong to say that the affine transform includes translation, rotation and anisotropic scaling, as John wants, but also shear, that he doesn't?<br>
<br>
John, similarity transformations include isotropic scaling, and in 2D they have 4 degrees of freedom (2 for translation + 1 for scaling + 1 for rotation).<br>
<br>
Affine transformations have 6 degrees of freedom, while the transformation you want would have 5 parameters (2 for translation + 2 for scaling + 1 for rotation).<br>
<br>
Maybe something you can do is combine an itk::ScaleTransform (anisotropic scaling) with an itk::Rigid2DTransform (translation and rotation).<br>
<br>
<a href="http://www.itk.org/Doxygen/html/classitk_1_1ScaleTransform.html" target="_blank">http://www.itk.org/Doxygen/html/classitk_1_1ScaleTransform.html</a><br>
<a href="http://www.itk.org/Doxygen/html/classitk_1_1Rigid2DTransform.html" target="_blank">http://www.itk.org/Doxygen/html/classitk_1_1Rigid2DTransform.html</a><br>
<br>
although swapping from one optimization to the other may not be worth the hassle, and you are better off just using an affine transformation, as Jinzhong suggests.<div class="im"><br>
<br>
Best regards,<br>
<br>
Ramon.<br>
<br>
-- <br>
Ramón Casero Cañas, DPhil<br>
<br>
Computational Biology, Computing Laboratory<br>
University of Oxford<br>
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<br>
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