ImageLuminance
VTKExamples/Cxx/Images/ImageLuminance
Description¶
There are two ways to convert images to greyscale:
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vtkImageLuminance uses the luminance equation for properly weighting the R, G, and B components;
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vtkImageMagnitude does a simple sum-of-squares computation of the components (i.e. the Euclidean norm -- not the quadratic mean!), and is meant for vector data.
For an example of usage of the vtkImageMagnitude filter, see ImageMagnitude.
Code¶
ImageLuminance.cxx
#include <vtkSmartPointer.h> #include <vtkImageData.h> #include <vtkImageMapper3D.h> #include <vtkImageCanvasSource2D.h> #include <vtkImageLuminance.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> #include <vtkInteractorStyleImage.h> #include <vtkRenderer.h> #include <vtkJPEGReader.h> #include <vtkImageActor.h> int main(int, char *[]) { // Create an image of a rectangle vtkSmartPointer<vtkImageCanvasSource2D> source = vtkSmartPointer<vtkImageCanvasSource2D>::New(); source->SetScalarTypeToUnsignedChar(); source->SetNumberOfScalarComponents(3); source->SetExtent(0, 200, 0, 200, 0, 0); // Clear the image source->SetDrawColor(0,0,0); source->FillBox(0,200,0,200); // Draw a red box source->SetDrawColor(255,0,0); source->FillBox(100,120,100,120); source->Update(); vtkSmartPointer<vtkImageLuminance> luminanceFilter = vtkSmartPointer<vtkImageLuminance>::New(); luminanceFilter->SetInputConnection(source->GetOutputPort()); luminanceFilter->Update(); // Create actors vtkSmartPointer<vtkImageActor> originalActor = vtkSmartPointer<vtkImageActor>::New(); originalActor->GetMapper()->SetInputConnection( source->GetOutputPort()); vtkSmartPointer<vtkImageActor> luminanceActor = vtkSmartPointer<vtkImageActor>::New(); luminanceActor->GetMapper()->SetInputConnection( luminanceFilter->GetOutputPort()); // Define viewport ranges // (xmin, ymin, xmax, ymax) double originalViewport[4] = {0.0, 0.0, 0.5, 1.0}; double luminanceViewport[4] = {0.5, 0.0, 1.0, 1.0}; // Setup renderers vtkSmartPointer<vtkRenderer> originalRenderer = vtkSmartPointer<vtkRenderer>::New(); originalRenderer->SetViewport(originalViewport); originalRenderer->AddActor(originalActor); originalRenderer->ResetCamera(); originalRenderer->SetBackground(.4, .5, .6); vtkSmartPointer<vtkRenderer> luminanceRenderer = vtkSmartPointer<vtkRenderer>::New(); luminanceRenderer->SetViewport(luminanceViewport); luminanceRenderer->AddActor(luminanceActor); luminanceRenderer->ResetCamera(); luminanceRenderer->SetBackground(.4, .5, .7); vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New(); renderWindow->SetSize(600, 300); renderWindow->AddRenderer(originalRenderer); renderWindow->AddRenderer(luminanceRenderer); vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New(); vtkSmartPointer<vtkInteractorStyleImage> style = vtkSmartPointer<vtkInteractorStyleImage>::New(); renderWindowInteractor->SetInteractorStyle(style); renderWindowInteractor->SetRenderWindow(renderWindow); renderWindowInteractor->Initialize(); renderWindowInteractor->Start(); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(ImageLuminance) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(ImageLuminance MACOSX_BUNDLE ImageLuminance.cxx) target_link_libraries(ImageLuminance ${VTK_LIBRARIES})
Download and Build ImageLuminance¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download ImageLuminance and its CMakeLists.txt file. Once the tarball ImageLuminance.tar has been downloaded and extracted,
cd ImageLuminance/build
If VTK is installed:
cmake ..
If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
Build the project:
make
and run it:
./ImageLuminance
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.