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ImageLuminance

vtk-examples/Cxx/Images/ImageLuminance

Description

There are two ways to convert images to greyscale:

For an example of usage of the vtkImageMagnitude filter, see ImageMagnitude.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

ImageLuminance.cxx

#include <vtkImageActor.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageLuminance.h>
#include <vtkImageMapper3D.h>
#include <vtkInteractorStyleImage.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // Create an image of a rectangle.
  vtkNew<vtkImageCanvasSource2D> source;
  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();

  vtkNew<vtkImageLuminance> luminanceFilter;
  luminanceFilter->SetInputConnection(source->GetOutputPort());
  luminanceFilter->Update();

  // Create actors
  vtkNew<vtkImageActor> originalActor;
  originalActor->GetMapper()->SetInputConnection(source->GetOutputPort());

  vtkNew<vtkImageActor> luminanceActor;
  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.
  vtkNew<vtkRenderer> originalRenderer;
  originalRenderer->SetViewport(originalViewport);
  originalRenderer->AddActor(originalActor);
  originalRenderer->ResetCamera();
  originalRenderer->SetBackground(
      colors->GetColor3d("CornflowerBlue").GetData());

  vtkNew<vtkRenderer> luminanceRenderer;
  luminanceRenderer->SetViewport(luminanceViewport);
  luminanceRenderer->AddActor(luminanceActor);
  luminanceRenderer->ResetCamera();
  luminanceRenderer->SetBackground(colors->GetColor3d("SteelBlue").GetData());

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(600, 300);
  renderWindow->AddRenderer(originalRenderer);
  renderWindow->AddRenderer(luminanceRenderer);
  renderWindow->SetWindowName("ImageLuminance");

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

  renderWindowInteractor->SetInteractorStyle(style);

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

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageLuminance)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageLuminance: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ImageLuminance MACOSX_BUNDLE ImageLuminance.cxx )
  target_link_libraries(ImageLuminance PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageLuminance
  MODULES ${VTK_LIBRARIES}
)

Download and Build ImageLuminance

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

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.