ImageMagnitude
VTKExamples/Cxx/Images/ImageMagnitude
Description
There are two ways to convert images to greyscale: {{class|vtkImageLuminance}} uses the [(video)|luminance equation]]([wikipedia:Luma) for properly weighting the R, G, and B components; {{class|vtkImageMagnitude}} does a simple sum-of-squares computation of the components (i.e. the [(mathematics)#Euclidean vector space|Euclidean norm]] -- not the [wikipedia:Root mean square|quadratic mean]!), and is meant for vector data.
For an example of usage of the vtkImageLuminance filter, see .
Code
ImageMagnitude.cxx
#include <vtkSmartPointer.h>
#include <vtkImageData.h>
#include <vtkImageMapper3D.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageMagnitude.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<vtkImageMagnitude> magnitudeFilter =
vtkSmartPointer<vtkImageMagnitude>::New();
magnitudeFilter->SetInputConnection(source->GetOutputPort());
magnitudeFilter->Update();
// Create actors
vtkSmartPointer<vtkImageActor> originalActor =
vtkSmartPointer<vtkImageActor>::New();
originalActor->GetMapper()->SetInputConnection(
source->GetOutputPort());
vtkSmartPointer<vtkImageActor> magnitudeActor =
vtkSmartPointer<vtkImageActor>::New();
magnitudeActor->GetMapper()->SetInputConnection(
magnitudeFilter->GetOutputPort());
// Define viewport ranges
// (xmin, ymin, xmax, ymax)
double originalViewport[4] = {0.0, 0.0, 0.5, 1.0};
double magnitudeViewport[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> magnitudeRenderer =
vtkSmartPointer<vtkRenderer>::New();
magnitudeRenderer->SetViewport(magnitudeViewport);
magnitudeRenderer->AddActor(magnitudeActor);
magnitudeRenderer->ResetCamera();
magnitudeRenderer->SetBackground(.4, .5, .7);
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->SetSize(600, 300);
renderWindow->AddRenderer(originalRenderer);
renderWindow->AddRenderer(magnitudeRenderer);
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(ImageMagnitude)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(ImageMagnitude MACOSX_BUNDLE ImageMagnitude.cxx)
target_link_libraries(ImageMagnitude ${VTK_LIBRARIES})
Download and Build ImageMagnitude
Click here to download ImageMagnitude and its CMakeLists.txt file. Once the tarball ImageMagnitude.tar has been downloaded and extracted,
cd ImageMagnitude/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:
./ImageMagnitude
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.