vtkLookupTable和图像透明度

#include <vtkImageActor.h>
#include <vtkImageData.h>
#include <vtkImageMapToColors.h>
#include <vtkImageMapper3D.h>
#include <vtkImageReader2.h>
#include <vtkImageReader2Factory.h>
#include <vtkInteractorStyleImage.h>
#include <vtkLookupTable.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include "vtkAutoInit.h"

VTK_MODULE_INIT(vtkRenderingFreeType)
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
VTK_MODULE_INIT(vtkRenderingVolumeOpenGL2);
int main(int argc, char* argv[])
{
    vtkNew<vtkNamedColors> colors;

    // Verify input arguments
    if (argc != 2)
    {
        std::cout << "Usage: " << argv[0] << " Filename(.jpg) e.g Gourds2.jpg"
            << std::endl;
        return EXIT_FAILURE;
    }

    // Read the image
    vtkNew<vtkImageReader2Factory> readerFactory;
    vtkSmartPointer<vtkImageReader2> reader;
    reader.TakeReference(readerFactory->CreateImageReader2(argv[1]));
    reader->SetFileName(argv[1]);
    reader->Update();

    vtkImageData* image = reader->GetOutput();

    // Create a mask - half of the image should be transparent and the other half
    // opaque
    vtkNew<vtkImageData> maskImage;
    int extent[6];
    image->GetExtent(extent);
    maskImage->SetExtent(extent);
    maskImage->AllocateScalars(VTK_DOUBLE, 1);

    for (int y = extent[2]; y < extent[3]; y++)
    {
        for (int x = extent[0]; x < extent[1]; x++)
        {
            double* pixel =
                static_cast<double*>(maskImage->GetScalarPointer(x, y, 0));
            if (y > (extent[3] - extent[2]) / 2.0)
            {
                pixel[0] = 0.0;
            }
            else
            {
                pixel[0] = 1.0;
            }
        }
    }

    vtkNew<vtkLookupTable> lookupTable;
    lookupTable->SetNumberOfTableValues(2);
    lookupTable->SetRange(0.0, 1.0);
    lookupTable->SetTableValue(1, 1.0, 0.0, 0.0, .7); // label 0 is transparent 标签 0是0.7透明的
    lookupTable->SetTableValue(
      0,
       colors->GetColor4d("Khaki").GetData()); // label 1 is opaque and colored
    lookupTable->Build();

    vtkNew<vtkImageMapToColors> mapTransparency;
    mapTransparency->SetLookupTable(lookupTable);
    mapTransparency->PassAlphaToOutputOn();
    mapTransparency->SetInputData(maskImage);

    // Create actors
    vtkNew<vtkImageActor> imageActor;
    imageActor->GetMapper()->SetInputData(image);

    vtkNew<vtkImageActor> maskActor;
    maskActor->GetMapper()->SetInputConnection(mapTransparency->GetOutputPort());

    // Visualize
    vtkNew<vtkRenderer> renderer;
    renderer->AddActor(imageActor);
    renderer->AddActor(maskActor);
    renderer->SetBackground(colors->GetColor3d("CornflowerBlue").GetData());
    renderer->ResetCamera();

    vtkNew<vtkRenderWindow> renderWindow;
    renderWindow->AddRenderer(renderer);
    renderWindow->SetWindowName("Transparency");

    vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
    vtkNew<vtkInteractorStyleImage> style;

    renderWindowInteractor->SetInteractorStyle(style);

    renderWindowInteractor->SetRenderWindow(renderWindow);
    renderWindow->Render();
    renderWindowInteractor->Initialize();
    renderWindowInteractor->Start();

    return EXIT_SUCCESS;
}