我们可以提取彩色的图像的各个颜色分量，那么同样也可以将灰度图像合并成为一个彩色图像。VTK中提供vtkImageAppendComponents类来合成彩色图像，其输入需要提供三个灰度图像。

下面实例：

#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL);#include <vtkSmartPointer.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageAppendComponents.h>
#include <vtkImageActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleImage.h>int main()
{vtkSmartPointer<vtkImageCanvasSource2D> red =vtkSmartPointer<vtkImageCanvasSource2D>::New();red->SetScalarTypeToUnsignedChar();red->SetNumberOfScalarComponents(1);red->SetExtent(0, 100, 0, 100, 0, 0);red->SetDrawColor(0, 0, 0, 0);red->FillBox(0, 100, 0, 100);red->SetDrawColor(255, 0, 0, 0);red->FillBox(20, 40, 20, 40);red->Update();vtkSmartPointer<vtkImageCanvasSource2D> green =vtkSmartPointer<vtkImageCanvasSource2D>::New();green->SetScalarTypeToUnsignedChar();green->SetNumberOfScalarComponents(1);green->SetExtent(0, 100, 0, 100, 0, 0);green->SetDrawColor(0, 0, 0, 0);green->FillBox(0, 100, 0, 100);green->SetDrawColor(255, 0, 0, 0);green->FillBox(30, 50, 30, 50);green->Update();vtkSmartPointer<vtkImageCanvasSource2D> blue =vtkSmartPointer<vtkImageCanvasSource2D>::New();blue->SetScalarTypeToUnsignedChar();blue->SetNumberOfScalarComponents(1);blue->SetExtent(0, 100, 0, 100, 0, 0);blue->SetDrawColor(0, 0, 0, 0);blue->FillBox(0, 100, 0, 100);blue->SetDrawColor(255, 0, 0, 0);blue->FillBox(40, 60, 40, 60);blue->Update();vtkSmartPointer<vtkImageAppendComponents> appendFilter =vtkSmartPointer<vtkImageAppendComponents>::New();appendFilter->SetInputConnection(0, red->GetOutputPort());appendFilter->AddInputConnection(0, green->GetOutputPort());appendFilter->AddInputConnection(0, blue->GetOutputPort());appendFilter->Update();vtkSmartPointer<vtkImageActor> redActor =vtkSmartPointer<vtkImageActor>::New();redActor->SetInputData(red->GetOutput());vtkSmartPointer<vtkImageActor> greenActor =vtkSmartPointer<vtkImageActor>::New();greenActor->SetInputData(green->GetOutput());vtkSmartPointer<vtkImageActor> blueActor =vtkSmartPointer<vtkImageActor>::New();blueActor->SetInputData(blue->GetOutput());vtkSmartPointer<vtkImageActor> combinedActor =vtkSmartPointer<vtkImageActor>::New();combinedActor->SetInputData(appendFilter->GetOutput());// Define viewport ranges// (xmin, ymin, xmax, ymax)double redViewport[4] = { 0.0, 0.0, 0.25, 1.0 };double greenViewport[4] = { 0.25, 0.0, 0.5, 1.0 };double blueViewport[4] = { 0.5, 0.0, 0.75, 1.0 };double combinedViewport[4] = { 0.75, 0.0, 1.0, 1.0 };// Setup renderersvtkSmartPointer<vtkRenderer> redRenderer =vtkSmartPointer<vtkRenderer>::New();redRenderer->SetViewport(redViewport);redRenderer->AddActor(redActor);redRenderer->ResetCamera();redRenderer->SetBackground(1.0, 1.0, 1.0);vtkSmartPointer<vtkRenderer> greenRenderer =vtkSmartPointer<vtkRenderer>::New();greenRenderer->SetViewport(greenViewport);greenRenderer->AddActor(greenActor);greenRenderer->ResetCamera();greenRenderer->SetBackground(1.0, 1.0, 1.0);vtkSmartPointer<vtkRenderer> blueRenderer =vtkSmartPointer<vtkRenderer>::New();blueRenderer->SetViewport(blueViewport);blueRenderer->AddActor(blueActor);blueRenderer->ResetCamera();blueRenderer->SetBackground(1.0, 1.0, 1.0);vtkSmartPointer<vtkRenderer> combinedRenderer =vtkSmartPointer<vtkRenderer>::New();combinedRenderer->SetViewport(combinedViewport);combinedRenderer->AddActor(combinedActor);combinedRenderer->ResetCamera();combinedRenderer->SetBackground(1.0, 1.0, 1.0);vtkSmartPointer<vtkRenderWindow> renderWindow =vtkSmartPointer<vtkRenderWindow>::New();renderWindow->AddRenderer(redRenderer);renderWindow->AddRenderer(greenRenderer);renderWindow->AddRenderer(blueRenderer);renderWindow->AddRenderer(combinedRenderer);renderWindow->SetSize(1200, 300);renderWindow->Render();renderWindow->SetWindowName("ImageAppendComponentsExample");vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =vtkSmartPointer<vtkRenderWindowInteractor>::New();vtkSmartPointer<vtkInteractorStyleImage> style =vtkSmartPointer<vtkInteractorStyleImage>::New();renderWindowInteractor->SetInteractorStyle(style);renderWindowInteractor->SetRenderWindow(renderWindow);renderWindowInteractor->Initialize();renderWindowInteractor->Start();return 0;
}

输出结果：

2.参看资料

1.《C++ primer》
2.《The VTK User’s Guide – 11thEdition》
3.《The Visualization Toolkit – AnObject-Oriented Approach To 3D Graphics (4th Edition)》
4.  张晓东, 罗火灵. VTK图形图像开发进阶[M]. 机械工业出版社, 2015.