[Insight-users] Problem with TransformPoint

[Clemens M. Hentschke]

Hi,

I want to transform points with the TransformPoint() method from one 
coordinate system (moving image) to another coordinate system (fixed image).
So far, I checked the transformation works fine by applying it to the 
image, the result image was as I expected correct.
As I am only interested in single pixels (and their respective 
transformed coordinates), I only used the TransformPoint() method of 
Similarity3DTransform insted of transforming the whole image.
I converted from pixel to physical coordinates on the moving image, 
transformed this coordinates and converted the physical coordinates to 
pixel coordinates on the fixed image.
However, the pixels from the moving image do not correspond to the fixed 
image.
I use ITK 3.20 with Windows 7 and the MinGW compiler.
Has anyone an idea what the problem may could be?
Thanks in advance.

I attached a code snippet:

typedef TransformType::InputPointType CenterType;

     typedef itk::Similarity3DTransform<double> TransformType;
     TransformType::Pointer transform =TransformType::New();

       CenterType center;
       center[0] = 3.3874403492;
       center[1] = -17.7840881162;
       center[2] = 50.2830146457;
       transform->SetCenter(center); // setting the center coordinates 
manually

       readerMoving->Update();
       readerFixed->Update();
       ImageType::Pointer mImage = readerMoving->GetOutput(); //the 
moving image
       ImageType::Pointer fImage = readerFixed->GetOutput(); //the fixed 
image

       TransformType::ParametersType 
paramsInput(transform->GetNumberOfParameters());
       paramsInput[0] = 0.244805;
       paramsInput[1] = 0.009105;
       paramsInput[2] = -0.056415;
       paramsInput[3] = -7.963562;
       paramsInput[4] = -29.462040;
       paramsInput[5] = 61.358929;
       paramsInput[6] = 0.981010;

       transform->SetParameters(paramsInput); //setting the parameters 
manually

       ImageType::IndexType indexIn;
       indexIn[0] = 162;  //some sample pixel from the moving image
       indexIn[1] = 218;
       indexIn[2] = 81;

       TransformType::InputPointType pt;

       mImage->TransformIndexToPhysicalPoint(indexIn, pt);

       TransformType::OutputPointType output =  
transform->TransformPoint(pt);

       ImageType::IndexType indexOut;
       fImage->TransformPhysicalPointToIndex(output, indexOut);

       for (int i=0; i<3; i++)
           cout << indexOut[i] << endl; //the output coordinates are 
obviously wrong, they do NOT match to the input (moving image) coordinates