/// <summary>
/// Gets the directional matrix (image orientation to the patient) from the DICOM dataset.
/// </summary>
/// <param name="dicomDataset">The DICOM dataset.</param>
/// <returns>The directional matrix (image orientation to the patient).</returns>
/// <exception cref="ArgumentNullException">The provided DICOM dataset was null.</exception>
/// <exception cref="ArgumentException">The provided DICOM dataset did not contain the 'ImageOrientationPatient' tag or the tag did not have 6 parts.</exception>
public static Matrix3 GetDirectionalMatrix(this DicomDataset dicomDataset)
{
dicomDataset = dicomDataset ?? throw new ArgumentNullException(nameof(dicomDataset));
// Extract the 2 3-dimensional points from the 'ImageOrientationPatient' DICOM attribute.
var imageOrientationPatientX = new Point3D(
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 0),
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 1),
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 2));
var imageOrientationPatientY = new Point3D(
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 3),
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 4),
dicomDataset.GetRequiredDicomAttribute <double>(DicomTag.ImageOrientationPatient, 5));
// Insist that the image orientations are of unit length, this is defined in the standard but
// rounding in serialization can cause them to be slightly off with respect to the double representation.
imageOrientationPatientX /= imageOrientationPatientX.Norm();
imageOrientationPatientY /= imageOrientationPatientY.Norm();
// The standard also insists iop[0] and iop[1] are orthogonal.
return(Matrix3.FromColumns(
imageOrientationPatientX,
imageOrientationPatientY,
Point3D.CrossProd(imageOrientationPatientX, imageOrientationPatientY)));
}
