ITK/VTK图像数据差别

 ITK与VTK的图像数据坐标的原点都在图像的左下角;

但是在读取图像时，二者的存储方式不同。以常用的dicom图像为例，图像的第一个像素定义为左上角。当使用VTK进行读取时，VTK将图像的第一个像素存储在左下角，因此，读取的图像是沿着Y轴反转的。而ITK则没有翻转的过程，其按照图像像素排列的原始顺序读入图像，然后将坐标原点移动到图像的左下角。二者图像数据读取方式的不同，导致二者之一的图像必须进行翻转，才能与另一个匹配。

ITK TO VTK ITK转化为VTK图像使用类

ITK/VTK数据转换的类均存放在ITKVTKGlue模块中。

  itkImageToVTKImageFilter 

#include <itkImageToVTKImageFilter.h>
#include "itkVTKImageIOFactory.h"
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkImageRegionIterator.h"

using PixelType = signed short;
constexpr unsigned int Dimension = 3;
  //初始化待读取序列的格式类型
  using ImageType = itk::Image<PixelType, Dimension>;
  using ReaderType = itk::ImageSeriesReader<ImageType>;
  using ImageIOType = itk::GDCMImageIO;
  using NamesGeneratorType = itk::GDCMSeriesFileNames;


  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
  auto connector1 = ConnectorType::New();
  connector1->SetInput(reader->GetOutput());
 
  connector1->Update();

VTK TO ITK  VTK转化为ITK图像使用类

itkVTKImagetoImageFilter

#include <itkVTKImageToImageFilter.h>
#include "itkVTKImageIOFactory.h"
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkImageRegionIterator.h"

using PixelType = signed short;
constexpr unsigned int Dimension = 3;
  //初始化待读取序列的格式类型
  using ImageType = itk::Image<PixelType, Dimension>;


vtkNew<vtkImageData> mTmpImageData;

typedef itk::VTKImageToImageFilter<ImageType> VTKImageToImageType;

VTKImageToImageType::Pointer vtkImageToImageFilter1 = VTKImageToImageType::New();
vtkImageToImageFilter1->SetInput(mTmpImageData);
  //vtkImageToImageFilter->SetInput(reader->GetOutput());
vtkImageToImageFilter1->Update();

注意事项

ITK/VTK二者图像数据互相转换后，可能会出现图像数据的spacing, direction, origin, position的变化，为了保证二者图像的一致性，常常需要人为设置这些参数 :

/*
an itk::Image and converts it into a vtkVolume, keeping it in DICOM's
patient physical world space. Its main usage is combining it with segmented
structures (vtkPolyData) whose vertices are in DICOM patient space, that
is, vertex coordinates were obtained using
*/
visualizing->TransformIndexToPhysicalPoint().
typedef itk::Image < unsigned char, 3 > ImageType;
void showITKimageInVTKqwidget(ImageType::Pointer visualizing)
{
     typedef itk::ImageToVTKImageFilter<ImageType> itkVtkConverter;
     itkVtkConverter::Pointer conv=itkVtkConverter::New();
     conv->SetInput(visualizing);
 
     vtkGPUVolumeRayCastMapper *mapper = vtkGPUVolumeRayCastMapper::New();
     mapper->SetInput(conv->GetOutput());
     vtkVolume *volume=vtkVolume::New();
     volume->SetProperty( myTransferFunction );
     volume->SetMapper( mapper );
 
     // vtkVolume only manages spacing by itself.
     // Here we take care of position and orientation so it is in DICOM physical space
  ImageType::DirectionType d=visualizing->GetDirection();
  vtkMatrix4x4 *mat=vtkMatrix4x4::New(); //identity matrix
  for (int i=0; i<3; i++)
    for (int k=0; k<3; k++)
      mat->SetElement(i,k, d(i,k));
  ImageType::PointType origin=visualizing->GetOrigin();
  volume->SetOrigin(-origin[0], -origin[1], -origin[2]);
  volume->SetPosition(-origin[0], -origin[1], -origin[2]);
  for (int i=0; i<3; i++)
    mat->SetElement(i,3, origin[i]);
  volume->SetUserMatrix(mat);
     vtkRenderer *renderer = myQWidget->GetRenderWindow()->GetRenderers()->GetFirstRenderer();
     renderer->AddVolume( volume );
     myQWidget->GetRenderWindow()->Render();
  renderer->ResetCamera();
}