[Insight-users] Apply Transform

[Oscar Esteban Sanz-Dranguet]

Hi Luis,

Following your recommendations, I've found that physical coordinates of 
Y axis are negative (¿?), so it was not a bug. The X and Z axis are 
positive. How can I detect if an axis should be accessed with negative 
coordinates? Should I use image->GetDirection()?

The other question I've found is 'what of the 12 criterions of 
definition of the Euler angles is using ITK?' After a quick search on 
the software guide, I didn't find it.

For the tests, I assumed the origin on (0,0,0) because I knew that it 
was certainly, but I've updated my code to take the origin into account 
:). I tested using only rotations referred to one axis and testing where 
a white point setted on the center was going.

Many thanks,
Oscar Esteban

Luis Ibanez escribió:
> Hi Steban,
>
> You code seem to be ok.
>
> However we are missing some important information from
> your image.
>
> In particular:
>
>
>      A) What are the coordinates of the Origin  ?
>           you can get this with   image->GetOrigin()
>
>      B) What is the orientation of the image ?
>           you can get this with    image->GetDirection()
>
>
> Your manual computation seems to assume that
> the origin coordinates are (0,0,0) and that the
> direction cosines are given  by an Identity matrix.
>
>
> If you want to understand the rotation of the image
> you should first experiment with Translations set
> to Zero.  Otherwise, as you probably know, a
> Rotation followed by a Translation will generate
> a different apparent center of rotation.
>
>
> You are also missing to include in your email the
> values that you are passing as angles for the
> Euler transform.
>
> Also, a screenshot of the output image that lead
> you to suspect that something is wrong, will be
> useful for this discussion. Could you please post
> this screenshot in a public web site ?
>
>
>
>      Thanks
>
>
>           Luis
>
>
> -------------------------------------------------------------------
> On Mon, Jun 29, 2009 at 1:24 PM, Oscar Esteban Sanz-Dranguet 
> <oesteban at die.upm.es <mailto:oesteban at die.upm.es>> wrote:
>
>     Hi,
>
>     I try to apply a rigid transform to some mri images. After
>     SetCenter, only rotation about Y axis seems to use this center.
>     Why I don't get the correct center of rotation about X and Z axis?
>     (code at the end)
>
>     Best Regards,
>     Oscar Esteban
>
>
>     <<<<<<<<<<<<<<<<< CODE >>>>>>>>>>>>>>>>>>>>>>
>     int main( int argc, char *argv[] )
>      {
>      if ( argc < 8 )
>       {
>       std::cerr << "Missing Parameters " << std::endl;
>       std::cerr << "Usage: " << argv[0];
>       std::cerr << " inputImageFile outputImageFile";
>       std::cerr << " traslationX traslationY traslationZ";
>       std::cerr << " rotationX rotationY rotationZ";
>       std::cerr << std::endl;
>       return 1;
>       }
>
>      typedef itk::ImageFileReader< ImageType > ImageReaderType;
>
>      typedef itk::Euler3DTransform< double > TransformType;
>
>      // Read images
>      ImageReaderType::Pointer  imageReader  = ImageReaderType::New();
>      imageReader->SetFileName( argv[1] );
>      imageReader->Update();
>      ImageType::Pointer  image =  imageReader->GetOutput();
>      ImageType::SpacingType spacing = image->GetSpacing();
>      ImageType::IndexType pixelCenter = { 128, 128, 58 };
>
>      image->SetPixel( pixelCenter, 255);
>
>      TransformType::Pointer      transform     = TransformType::New();
>
>      TransformType::InputPointType center;
>      center[0] = 128.5 * spacing[0];
>      center[1] = 128.5 * spacing[1];
>      center[2] = 58.5 *  spacing[2];
>      transform->SetCenter( center );
>
>      TransformType::OutputVectorType translation;
>      translation[0] = atof( argv[3] ) * spacing[0];
>      translation[1] = atof( argv[4] ) * spacing[1];
>      translation[2] = atof( argv[5] ) * spacing[2];
>
>      transform->SetRotation( deg2rad( atof( argv[6] ) ), deg2rad(
>     atof( argv[7] ) ), deg2rad( atof( argv[8] ) ) );
>      transform->SetTranslation( translation );
>
>      transform->Print(std::cout, 3);
>
>      typedef itk::ResampleImageFilter< ImageType, ImageType >  
>      ResampleFilterType;
>      ResampleFilterType::Pointer resampler = ResampleFilterType::New();
>
>      resampler->SetTransform( transform );
>      resampler->SetInput( image );
>      resampler->SetReferenceImage( image );
>      resampler->UseReferenceImageOn( );
>      resampler->Update();
>
>      typedef itk::ImageFileWriter< ImageType >  WriterType;
>      WriterType::Pointer writer =  WriterType::New();
>      writer->SetFileName( argv[2] );
>      writer->SetInput( resampler->GetOutput() );
>      writer->Update();
>
>      return EXIT_SUCCESS;
>      }
>
>
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