from vtk to OpenCV

[Xianjie Li]

Now I want convert vtkImageData to OpenCV Mat/IplImage.but the image that I processed is not expected.

I think it should be the data type,I try every type,but it doesn't work.

Can somebody help me?

[Xianjie Li]

code is here:        

        vtkDICOMImageReader*reader = vtkDICOMImageReader::New();

reader->SetFileName("D:\\DicomData\\SE6\\IM24");

reader->Update();

vtkImageData *imageData_1 = vtkImageData::New();

imageData_1->DeepCopy(reader->GetOutput());

vtkImageCast*caster = vtkImageCast::New();

caster->SetInput(imageData_1);

caster->SetOutputScalarTypeToUnsignedChar();

caster->Update();

vtkExtractVOI*extractVOI = vtkExtractVOI::New();

extractVOI->SetInput(caster->GetOutput());

int dims[3];

imageData_1->GetDimensions(dims);

extractVOI->SetVOI(0, dims[0], 0, dims[1], 0, 0); // Set it to z=75

extractVOI->GetOutput()->SetScalarTypeToDouble();

cv::Mat image(dims[0], dims[1], CV_8UC1);

extractVOI->Update();

for (int i=0; i<dims[0]; ++i) 

{

for (int j=0; j<dims[1]; ++j) 

{

image.at<unsigned char>(cv::Point(j,i)) = *static_cast<unsigned char*>(extractVOI->GetOutput()->GetScalarPointer(i,j,0));

}

}

在 2015年4月29日星期三 UTC+8下午2:44:30，Xianjie Li写道：

[Luca Antiga]

Hello Xianjie,

the problem here is that your original pixel type is not 8-bit (very likely 16-bit),

so its range will be well outside 0-255.

vtkImageCast is only changing the numeric type of the data array, but it won’t 

rescale your original values to the 0-255 range, you have to do it before casting.

So, what happens is that your values wrap around (i.e. 256->0, 257->1, ...), resulting

in the funny image you see in OpenCV).

If you want to stay in vtk-land, you can use vtkImageShiftScale instead of vtkImageCast

…

// first define window (the width of the intensity range you want to map to 0-255) and level (the center of the intensity range you want to map to 0-255)

double window = 500.0;

double level = 50.0;

vtkImageShiftScale* shiftScale = vtkImageShiftScale::New();

shiftScale->SetInput(imageData_1);

shiftScale->SetShift(-(level - 0.5*window));

shiftScale->SetScale(255.0/window);

shiftScale->SetOutputScalarTypeToUnsignedChar();

shiftScale->ClampOverflowOn();

shiftScale->Update();

vtkExtractVOI*extractVOI = vtkExtractVOI::New();

extractVOI->SetInput(shiftScale->GetOutput());

… 

Hope this helps

Luca

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[Xianjie Li]

yeah,it works,Thank you Luca!

在 2015年5月1日星期五 UTC+8下午9:42:53，Luca Antiga写道：