子类指针不能转换为父类指针？？？_vs编译器报无法从子类指针转换为父类指针-优快云博客

本文链接：https://blog.youkuaiyun.com/majcos/article/details/1523971

本文介绍了一种在使用VTK库进行三维图像处理时遇到的编译错误，并详细解释了错误原因及解决方法。主要问题是由于缺少特定子类的头文件引入，导致编译器无法识别类间的继承关系。

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编译一程序，出现如下错误：
main.cpp(51) : error C2664: 'void __thiscall vtkVolumeMapper::SetInput(class vtkImageData *)' : cannot convert parameter 1 from 'class vtkStructuredPoints *' to 'class vtkImageData *'

vtkStructuredPoints是vtkImageData的子类，为何会有上述错误？原来是没有“#include "vtkStructuredPoints.h"（子类的头文件）”。因为没有这个头文件，编译器根本不知道这两个类之间有继承关系。

#include "vtkActor.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkProperty.h"
#include "vtkStructuredPointsReader.h"
#include "vtkStructuredPoints.h"//没有这一行就会出现上述错误
#include "vtkPiecewiseFunction.h"
#include "vtkColorTransferFunction.h"
#include "vtkVolumeProperty.h"
#include "vtkVolumeRayCastCompositeFunction.h"
#include "vtkVolumeRayCastMapper.h"
#include "vtkVolume.h"

void main ()
{
    vtkRenderer *ren = vtkRenderer::New();
    vtkRenderWindow *renWin = vtkRenderWindow::New();
    renWin->AddRenderer(ren);
    vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
    iren->SetRenderWindow(renWin);

    vtkStructuredPointsReader *reader = vtkStructuredPointsReader::New();
    reader->SetFileName("./Data/ironProt.vtk");

    vtkPiecewiseFunction *opacityTransferFunction =
        vtkPiecewiseFunction::New();
    opacityTransferFunction->AddPoint(20, 0.0);
    opacityTransferFunction->AddPoint(255, 0.2);

    vtkColorTransferFunction *colorTransferFunction =
        vtkColorTransferFunction::New();
    colorTransferFunction->AddRGBPoint(0.0, 0.0, 0.0, 0.0);
    colorTransferFunction->AddRGBPoint(64.0, 1.0, 0.0, 0.0);
    colorTransferFunction->AddRGBPoint(128.0, 0.0, 0.0, 1.0);
    colorTransferFunction->AddRGBPoint(192.0, 0.0, 1.0, 0.0);
    colorTransferFunction->AddRGBPoint(255.0, 0.0, 0.2, 0.0);

    vtkVolumeProperty *volumeProperty = vtkVolumeProperty::New();
    volumeProperty->SetColor(colorTransferFunction);
    volumeProperty->SetScalarOpacity(opacityTransferFunction);
    volumeProperty->ShadeOn();
    volumeProperty->SetInterpolationTypeToLinear();

    vtkVolumeRayCastCompositeFunction *compositeFunction =
        vtkVolumeRayCastCompositeFunction::New();
    vtkVolumeRayCastMapper *volumeMapper =
        vtkVolumeRayCastMapper::New();
    volumeMapper->SetVolumeRayCastFunction(compositeFunction);
    //volumeMapper->SetInputConnection(reader->GetOutputPort());
    volumeMapper->SetInput(reader->GetOutput());

    vtkVolume *volume = vtkVolume::New();
    volume->SetMapper(volumeMapper);
    volume->SetProperty(volumeProperty);

    ren->AddVolume(volume);
    ren->SetBackground(1, 1, 1);
    renWin->SetSize(600, 600);
    renWin->Render();

    iren->Initialize();
    renWin->Render();
    iren->Start();
}