ImageHistogram

VTKExamples/Cxx/Images/ImageHistogram


Code

ImageHistogram.cxx

#include <vtkSmartPointer.h>
#include <vtkImageHistogram.h>

#include <vtkImageReader2Factory.h>
#include <vtkImageReader2.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleImage.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkCamera.h>
#include <vtkImageData.h>
#include <vtkImageSliceMapper.h>
#include <vtkImageProperty.h>
#include <vtkImageSlice.h>

int main(int argc, char *argv[])
{
  if( argc < 2 )
  {
    std::cout << "Usage: " << argv[0] << " filename" << std::endl;
    return EXIT_FAILURE;
  }
  vtkSmartPointer<vtkRenderWindowInteractor> iren =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  vtkSmartPointer<vtkInteractorStyle> style =
    vtkSmartPointer<vtkInteractorStyle>::New();
  vtkSmartPointer<vtkRenderWindow> renWin =
    vtkSmartPointer<vtkRenderWindow>::New();
  iren->SetRenderWindow(renWin);
  iren->SetInteractorStyle(style);

  vtkSmartPointer<vtkImageReader2Factory> readerFactory =
    vtkSmartPointer<vtkImageReader2Factory>::New();
  vtkImageReader2 *reader = readerFactory->CreateImageReader2(argv[1]);
  reader->SetFileName(argv[1]);

  vtkSmartPointer<vtkImageHistogram> histogram =
    vtkSmartPointer<vtkImageHistogram>::New();
  histogram->SetInputConnection(reader->GetOutputPort());
  histogram->GenerateHistogramImageOn();
  histogram->SetHistogramImageSize(256,256);
  histogram->SetHistogramImageScaleToSqrt();
  histogram->AutomaticBinningOn();
  histogram->Update();

  vtkIdType nbins = histogram->GetNumberOfBins();
  double range[2];
  range[0] = histogram->GetBinOrigin();
  range[1] = range[0] + (nbins - 1)*histogram->GetBinSpacing();

  for (int i = 0; i < 2; i++)
  {
    vtkSmartPointer<vtkRenderer> renderer =
      vtkSmartPointer<vtkRenderer>::New();
    vtkCamera *camera = renderer->GetActiveCamera();
    renderer->SetViewport(0.5*(i&1), 0.0,
                          0.5 + 0.5*(i&1), 1.0);
    renWin->AddRenderer(renderer);

    vtkSmartPointer<vtkImageSliceMapper> imageMapper =
      vtkSmartPointer<vtkImageSliceMapper>::New();
    // compute y range
    double yd;
    if ((i & 1) == 0)
    {
      imageMapper->SetInputConnection(reader->GetOutputPort());
      int extent[6];
      reader->GetOutput()->GetExtent(extent);
      yd = (extent[3] - extent[2] + 1);
    }
    else
    {
      imageMapper->SetInputConnection(histogram->GetOutputPort());
      imageMapper->BorderOn();
      int extent[6];
      histogram->GetOutput()->GetExtent(extent);
      yd = (extent[3] - extent[2] + 1);
    }

    const double *bounds = imageMapper->GetBounds();
    double point[3];
    point[0] = 0.5*(bounds[0] + bounds[1]);
    point[1] = 0.5*(bounds[2] + bounds[3]);
    point[2] = 0.5*(bounds[4] + bounds[5]);

    camera->SetFocalPoint(point);
    point[imageMapper->GetOrientation()] += 1000;
    camera->SetPosition(point);
    camera->SetViewUp(0.0, 1.0, 0.0);
    camera->ParallelProjectionOn();
    // Set scale so that vertical dimension fills the window
    camera->SetParallelScale(0.5 * yd);

    vtkSmartPointer<vtkImageSlice> image =
      vtkSmartPointer<vtkImageSlice>::New();
    image->SetMapper(imageMapper);

    renderer->AddViewProp(image);

    if ((i & 1) == 0)
    {
      image->GetProperty()->SetColorWindow(range[1] - range[0]);
      image->GetProperty()->SetColorLevel(0.5*(range[0] + range[1]));
    }
    else
    {
      image->GetProperty()->SetInterpolationTypeToNearest();
      image->GetProperty()->SetColorWindow(255.0);
      image->GetProperty()->SetColorLevel(127.5);
    }
  }

  renWin->SetSize(640, 480);

  iren->Initialize();
  renWin->Render();
  iren->Start();
  reader->Delete();
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

PROJECT(ImageHistogram)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(ImageHistogram MACOSX_BUNDLE ImageHistogram.cxx )

target_link_libraries(ImageHistogram ${VTK_LIBRARIES})

Download and Build ImageHistogram

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

cd ImageHistogram/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:

./ImageHistogram

WINDOWS USERS

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