# RGBToHSV

VTKExamples/Cxx/Images/RGBToHSV

### Description

Convert RGB channels to HSV channels. See this article for a description of the RGB colormodel.

Seealso

RGBToYIQ and RGBToHSI

### Code

RGBToHSV.cxx

    #include <vtkSmartPointer.h>
    #include <vtkImageRGBToHSV.h>

    #include <vtkImageReader2Factory.h>
    #include <vtkImageReader2.h>
    #include <vtkImageData.h>
    #include <vtkImageMapper3D.h>
    #include <vtkCamera.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkRenderer.h>
    #include <vtkImageActor.h>
    #include <vtkImageExtractComponents.h>
    #include <vtkNamedColors.h>

    int main(int argc, char *argv[])
    {
      // Verify command line arguments
      if(argc != 2)
      {
        std::cerr << "Usage: " << argv[0] << "image" << std::endl;
        return EXIT_FAILURE;
      }

      // Read the image
      vtkSmartPointer<vtkImageReader2Factory> readerFactory =
        vtkSmartPointer<vtkImageReader2Factory>::New();
      vtkSmartPointer<vtkImageReader2> reader;
      reader.TakeReference(
        readerFactory->CreateImageReader2(argv[1]));
      reader->SetFileName(argv[1]);

      vtkSmartPointer<vtkImageRGBToHSV> hsvFilter =
        vtkSmartPointer<vtkImageRGBToHSV>::New();
      hsvFilter->SetInputConnection(reader->GetOutputPort());

      vtkSmartPointer<vtkImageExtractComponents> extractHueFilter =
        vtkSmartPointer<vtkImageExtractComponents>::New();
      extractHueFilter->SetInputConnection(hsvFilter->GetOutputPort());
      extractHueFilter->SetComponents(0);

      vtkSmartPointer<vtkImageExtractComponents> extractSaturationFilter =
        vtkSmartPointer<vtkImageExtractComponents>::New();
      extractSaturationFilter->SetInputConnection(hsvFilter->GetOutputPort());
      extractSaturationFilter->SetComponents(1);

      vtkSmartPointer<vtkImageExtractComponents> extractValueFilter =
        vtkSmartPointer<vtkImageExtractComponents>::New();
      extractValueFilter->SetInputConnection(hsvFilter->GetOutputPort());
      extractValueFilter->SetComponents(2);

      // Create actors
      vtkSmartPointer<vtkImageActor> inputActor =
        vtkSmartPointer<vtkImageActor>::New();
      inputActor->GetMapper()->SetInputConnection(
        reader->GetOutputPort());

      vtkSmartPointer<vtkImageActor> hActor =
        vtkSmartPointer<vtkImageActor>::New();
      hActor->GetMapper()->SetInputConnection(
        extractHueFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> sActor =
        vtkSmartPointer<vtkImageActor>::New();
      sActor->GetMapper()->SetInputConnection(
        extractSaturationFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> vActor =
        vtkSmartPointer<vtkImageActor>::New();
      vActor->GetMapper()->SetInputConnection(
        extractValueFilter->GetOutputPort());

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double inputViewport[4] = {0.0, 0.0, 0.25, 1.0};
      double hViewport[4] = {0.25, 0.0, 0.5, 1.0};
      double sViewport[4] = {0.5, 0.0, 0.75, 1.0};
      double vViewport[4] = {0.75, 0.0, 1.0, 1.0};

      // Shared camera
      vtkSmartPointer<vtkCamera> sharedCamera =
        vtkSmartPointer<vtkCamera>::New();

      // Setup renderers
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();
      vtkSmartPointer<vtkRenderer> inputRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      inputRenderer->SetViewport(inputViewport);
      inputRenderer->AddActor(inputActor);
      inputRenderer->SetActiveCamera(sharedCamera);
      inputRenderer->SetBackground(colors->GetColor3d("Tomato").GetData());

      vtkSmartPointer<vtkRenderer> hRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      hRenderer->SetViewport(hViewport);
      hRenderer->AddActor(hActor);
      hRenderer->SetActiveCamera(sharedCamera);
      hRenderer->SetBackground(colors->GetColor3d("Gainsboro").GetData());

      vtkSmartPointer<vtkRenderer> sRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      sRenderer->SetViewport(sViewport);
      sRenderer->AddActor(sActor);
      sRenderer->SetActiveCamera(sharedCamera);
      sRenderer->SetBackground(colors->GetColor3d("LightGrey").GetData());

      vtkSmartPointer<vtkRenderer> vRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      vRenderer->SetViewport(vViewport);
      vRenderer->AddActor(vActor);
      vRenderer->SetActiveCamera(sharedCamera);
      vRenderer->SetBackground(colors->GetColor3d("Silver").GetData());

      // Setup render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(1000, 250);
      renderWindow->AddRenderer(inputRenderer);
      renderWindow->AddRenderer(hRenderer);
      renderWindow->AddRenderer(sRenderer);
      renderWindow->AddRenderer(vRenderer);
      inputRenderer->ResetCamera();

      // Setup render window interactor
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();

      renderWindowInteractor->SetInteractorStyle(style);

      // Render and start interaction
      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderWindow->Render();
      renderWindowInteractor->Initialize();

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(RGBToHSV)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonDataModel
      vtkIOImage
      vtkImagingColor
      vtkImagingCore
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping RGBToHSV: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(RGBToHSV MACOSX_BUNDLE RGBToHSV.cxx )
      target_link_libraries(RGBToHSV PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(RGBToHSV MACOSX_BUNDLE RGBToHSV.cxx )
      target_link_libraries(RGBToHSV PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS RGBToHSV
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build RGBToHSV

Click here to download RGBToHSV and its CMakeLists.txt file. Once the tarball RGBToHSV.tar has been downloaded and extracted,

    cd RGBToHSV/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:

    ./RGBToHSV

WINDOWS USERS

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