ITK/Examples/Statistics/ImageToHistogramFilterRGB

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ImageToHistogramFilterRGB.cxx

#include "itkRGBPixel.h"
#include "itkImage.h"
#include "itkImageToHistogramFilter.h"
#include "itkImageRandomIteratorWithIndex.h"
 
typedef itk::RGBPixel<unsigned char> RGBPixelType;
typedef itk::Image< RGBPixelType, 2> ImageType;
 
void CreateImage(ImageType::Pointer image);
 
int main(int, char *[])
{
  const unsigned int MeasurementVectorSize = 3; // RGB
  const unsigned int binsPerDimension = 4;
 
  ImageType::Pointer image = ImageType::New();
  CreateImage(image);
 
  typedef itk::Statistics::ImageToHistogramFilter< ImageType > ImageToHistogramFilterType;
 
  ImageToHistogramFilterType::HistogramType::MeasurementVectorType lowerBound(MeasurementVectorSize);
  lowerBound.Fill(0);
 
  ImageToHistogramFilterType::HistogramType::MeasurementVectorType upperBound(MeasurementVectorSize);
  upperBound.Fill(255) ;
 
  ImageToHistogramFilterType::HistogramType::SizeType size(MeasurementVectorSize);
  size.Fill(binsPerDimension);
 
  ImageToHistogramFilterType::Pointer imageToHistogramFilter = ImageToHistogramFilterType::New();
  imageToHistogramFilter->SetInput(image);
  imageToHistogramFilter->SetHistogramBinMinimum(lowerBound);
  imageToHistogramFilter->SetHistogramBinMaximum(upperBound);
  imageToHistogramFilter->SetHistogramSize(size);
  imageToHistogramFilter->SetAutoMinimumMaximum(false);
  imageToHistogramFilter->Update();
 
  ImageToHistogramFilterType::HistogramType* histogram = imageToHistogramFilter->GetOutput();
 
  unsigned int totalBins = 1;
  for(unsigned int i = 0; i < size.GetNumberOfElements(); ++i)
    {
    totalBins *= histogram->GetSize()[i];
    }
  std::cout << "totalBins: " << totalBins << std::endl;
 
  std::cout << "Frequency = ";
  for(unsigned int i = 0; i < totalBins; ++i)
    {
    std::cout << histogram->GetFrequency(i) << " ";
    }
 
  std::cout << std::endl;
 
  return EXIT_SUCCESS;
}
 
void CreateImage(ImageType::Pointer image)
{
  // Create a black image with a red square and a green square.
  // This should produce a histogram with very strong spikes.
  itk::Size<2> size;
  size.Fill(10);
 
  itk::Index<2> start;
  start.Fill(0);
 
  itk::ImageRegion<2> region(start, size);
 
  image->SetRegions(region);
  image->Allocate();
 
  RGBPixelType zeroPixel;
  zeroPixel.SetRed(0);
  zeroPixel.SetGreen(0);
  zeroPixel.SetBlue(0);
 
  image->FillBuffer(zeroPixel);
 
  RGBPixelType pixel;
  pixel.SetRed(110);
  pixel.SetGreen(110);
  pixel.SetBlue(110);
 
  itk::ImageRandomIteratorWithIndex<ImageType> imageIterator(image, image->GetLargestPossibleRegion());
  imageIterator.SetNumberOfSamples(10);
 
  while(!imageIterator.IsAtEnd())
    {
    std::cout << "Setting pixel " << imageIterator.GetIndex() << " to " << pixel << std::endl;
    imageIterator.Set(pixel);
    ++imageIterator;
    }
 
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.9.5)
 
project(ImageToHistogramFilterRGB)
 
find_package(ITK REQUIRED)
include(${ITK_USE_FILE})
if (ITKVtkGlue_LOADED)
  find_package(VTK REQUIRED)
  include(${VTK_USE_FILE})
endif()
 
add_executable(ImageToHistogramFilterRGB MACOSX_BUNDLE ImageToHistogramFilterRGB.cxx)
 
if( "${ITK_VERSION_MAJOR}" LESS 4 )
  target_link_libraries(ImageToHistogramFilterRGB ITKReview ${ITK_LIBRARIES})
else( "${ITK_VERSION_MAJOR}" LESS 4 )
  target_link_libraries(ImageToHistogramFilterRGB ${ITK_LIBRARIES})
endif( "${ITK_VERSION_MAJOR}" LESS 4 )

Download and Build ImageToHistogramFilterRGB

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

cd ImageToHistogramFilterRGB/build
  • If ITK is installed:
cmake ..
  • If ITK is not installed but compiled on your system, you will need to specify the path to your ITK build:
cmake -DITK_DIR:PATH=/home/me/itk_build ..

Build the project:

make

and run it:

./ImageToHistogramFilterRGB

WINDOWS USERS PLEASE NOTE: Be sure to add the ITK bin directory to your path. This will resolve the ITK dll's at run time.

Building All of the Examples

Many of the examples in the ITK Wiki Examples Collection require VTK. You can build all of the the examples by following these instructions. If you are a new VTK user, you may want to try the Superbuild which will build a proper ITK and VTK.

ItkVtkGlue

ITK >= 4

For examples that use QuickView (which depends on VTK), you must have built ITK with Module_ITKVtkGlue=ON.

ITK < 4

Some of the ITK Examples require VTK to display the images. If you download the entire ITK Wiki Examples Collection, the ItkVtkGlue directory will be included and configured. If you wish to just build a few examples, then you will need to download ItkVtkGlue and build it. When you run cmake it will ask you to specify the location of the ItkVtkGlue binary directory.