vtk coordinate conversion: UI mouse location is obtained from a pixel value

Get the mouse position

//QVTKInteractor* m_interactor;

int eventPosition[2];
m_interactor->GetEventPosition(eventPosition);

Get the mouse position from the world coordinate position

//vtkSmartPointer<vtkRenderer> m_renderer;

vtkNew<vtkCoordinate> coordinate;
coordinate->SetCoordinateSystemToDisplay();
coordinate->SetValue(viewportPosition);
double* worldCoordinate = coordinate->GetComputedWorldValue(m_renderer);

Get the pixel coordinates of the world coordinate and pixel spacing gap

vtkImageData* imageData = m_reader->GetOutput();
double spacing[2];
imageData->GetSpacing(spacing);

int x = std::round(worldCoordinate[0] / spacing[0]);
int y = std::round(worldCoordinate[1] / spacing[1]);

Acquiring a pixel value for each pixel according to the number of bytes stored

int z = 0;
//各个维度的像素范围
int dims[2];
imageData->GetDimensions(dims);

string text = "";
if ((x >= 0 && x < dims[0]) && (y >= 0 && y < dims[1]))
{
	int SamplePerPixel = GetSamplesPerPixel();
	if (SamplePerPixel == 1)
	{
		auto pixelValue = (short *)imageData->GetScalarPointer(x, y, z);
		text = "X:" + to_string(x) + " Y:" + to_string(y) + " Val:" + to_string(*pixelValue);
	}
	else if (SamplePerPixel == 3)
	{
		auto pixelValue = (unsigned char *)imageData->GetScalarPointer(x, y, z);
		text = "X:" + to_string(x)
			+ " Y:" + to_string(y)
			+ " Val:" 
			+ to_string(*pixelValue) + ","
			+ to_string(*(pixelValue + 1)) + ","
			+ to_string(*(pixelValue + 2));
	}
}

Wherein each pixel has acquired several bytes storing pixel values

int Reader::GetSamplesPerPixel()
{
	return m_metaData->GetAttributeValue(DC::SamplesPerPixel).AsInt();
}