# HybridMedianComparison

VTKExamples/Cxx/ImageProcessing/HybridMedianComparison

### Description¶

Comparison of median and hybrid-median filters. The hybrid filter preserves corners and thin lines, better than the median filter. The lower patterns represent the three neighborhoods used to compute the hybrid median.

Other Languages

See (Python)

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code¶

HybridMedianComparison.cxx

#include <vtkCamera.h>
#include <vtkDataArray.h>
#include <vtkImageActor.h>
#include <vtkImageCast.h>
#include <vtkImageData.h>
#include <vtkImageHybridMedian2D.h>
#include <vtkImageMapper3D.h>
#include <vtkImageMathematics.h>
#include <vtkImageMedian3D.h>
#include <vtkImageNoiseSource.h>
#include <vtkImageProperty.h>
#include <vtkImageReader2.h>
#include <vtkImageReader2Factory.h>
#include <vtkImageThreshold.h>
#include <vtkInteractorStyleImage.h>
#include <vtkPointData.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>

#include <vector>

namespace
{
void AddShotNoise(vtkSmartPointer<vtkImageData> &inputImage,
vtkSmartPointer<vtkImageData> &outputImage,
double amplitude,
double noiseFraction,
int extent[6]);
}
int main (int argc, char *argv[])
{
// Verify input arguments
if ( argc != 2 )
{
std::cout << "Usage: " << argv[0]
<< " Filename" << 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]);
reader->Update();

int scalarRange[2];
scalarRange[0] =
reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[0];
scalarRange[1] =
reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[1];
std::cout << "Range: "
<< scalarRange[0] << ", " << scalarRange[1]
<< std::endl;
int middleSlice = (reader->GetOutput()->GetExtent()[5] -
reader->GetOutput()->GetExtent()[4]) / 2;

// Work with double images
vtkSmartPointer<vtkImageCast> cast =
vtkSmartPointer<vtkImageCast>::New();
cast->SetInputConnection(reader->GetOutputPort());
cast->SetOutputScalarTypeToDouble();
cast->Update();

vtkSmartPointer<vtkImageData> originalData =
vtkSmartPointer<vtkImageData>::New();
originalData->DeepCopy(cast->GetOutput());

vtkSmartPointer<vtkImageData> noisyData =
vtkSmartPointer<vtkImageData>::New();

AddShotNoise(originalData, noisyData,
2000.0, .1, reader->GetOutput()->GetExtent());
vtkSmartPointer<vtkImageMedian3D> median =
vtkSmartPointer<vtkImageMedian3D>::New();
median->SetInputData(noisyData);
median->SetKernelSize(5, 5, 1);

vtkSmartPointer<vtkImageHybridMedian2D> hybridMedian1 =
vtkSmartPointer<vtkImageHybridMedian2D>::New();
hybridMedian1->SetInputData(noisyData);
vtkSmartPointer<vtkImageHybridMedian2D> hybridMedian =
vtkSmartPointer<vtkImageHybridMedian2D>::New();
hybridMedian->SetInputConnection(hybridMedian1->GetOutputPort());

int colorWindow = (scalarRange[1] - scalarRange[0]);
int colorLevel = colorWindow / 2;
vtkSmartPointer<vtkImageActor> originalActor =
vtkSmartPointer<vtkImageActor>::New();
originalActor->GetMapper()->SetInputData(originalData);
originalActor->GetProperty()->SetColorWindow(colorWindow);
originalActor->GetProperty()->SetColorLevel(colorLevel);
originalActor->GetProperty()->SetInterpolationTypeToNearest();
originalActor->SetDisplayExtent(
reader->GetDataExtent()[0], reader->GetDataExtent()[1],
reader->GetDataExtent()[2], reader->GetDataExtent()[3],
middleSlice, middleSlice);

vtkSmartPointer<vtkImageActor> noisyActor =
vtkSmartPointer<vtkImageActor>::New();
noisyActor->GetMapper()->SetInputData(noisyData);
noisyActor->GetProperty()->SetColorWindow(colorWindow);
noisyActor->GetProperty()->SetColorLevel(colorLevel);
noisyActor->GetProperty()->SetInterpolationTypeToNearest();
noisyActor->SetDisplayExtent(originalActor->GetDisplayExtent());

vtkSmartPointer<vtkImageActor> hybridMedianActor =
vtkSmartPointer<vtkImageActor>::New();
hybridMedianActor->GetMapper()->SetInputConnection(hybridMedian->GetOutputPort());
hybridMedianActor->GetProperty()->SetColorWindow(colorWindow);
hybridMedianActor->GetProperty()->SetColorLevel(colorLevel);
hybridMedianActor->GetProperty()->SetInterpolationTypeToNearest();
hybridMedianActor->SetDisplayExtent(originalActor->GetDisplayExtent());

vtkSmartPointer<vtkImageActor> medianActor =
vtkSmartPointer<vtkImageActor>::New();
medianActor->GetMapper()->SetInputConnection(median->GetOutputPort());
medianActor->GetProperty()->SetColorWindow(colorWindow);
medianActor->GetProperty()->SetColorLevel(colorLevel);
medianActor->GetProperty()->SetInterpolationTypeToNearest();
medianActor->SetDisplayExtent(originalActor->GetDisplayExtent());

// Setup renderers
vtkSmartPointer<vtkRenderer> originalRenderer =
vtkSmartPointer<vtkRenderer>::New();
originalRenderer->AddActor(originalActor);
vtkSmartPointer<vtkRenderer> noisyRenderer =
vtkSmartPointer<vtkRenderer>::New();
noisyRenderer->AddActor(noisyActor);
vtkSmartPointer<vtkRenderer> hybridRenderer =
vtkSmartPointer<vtkRenderer>::New();
hybridRenderer->AddActor(hybridMedianActor);
vtkSmartPointer<vtkRenderer> medianRenderer =
vtkSmartPointer<vtkRenderer>::New();
medianRenderer->AddActor(medianActor);

std::vector<vtkSmartPointer<vtkRenderer> > renderers;
renderers.push_back(originalRenderer);
renderers.push_back(noisyRenderer);
renderers.push_back(hybridRenderer);
renderers.push_back(medianRenderer);

// Setup viewports for the renderers
int rendererSize = 400;
unsigned int xGridDimensions = 2;
unsigned int yGridDimensions = 2;

vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->SetSize(
rendererSize * xGridDimensions, rendererSize * yGridDimensions);
for (int row = 0; row < static_cast<int>(yGridDimensions); row++)
{
for (int col = 0; col < static_cast<int>(xGridDimensions); col++)
{
int index = row * xGridDimensions + col;
// (xmin, ymin, xmax, ymax)
double viewport[4] = {
static_cast<double>(col) / xGridDimensions,
static_cast<double>(yGridDimensions - (row + 1)) / yGridDimensions,
static_cast<double>(col + 1) / xGridDimensions,
static_cast<double>(yGridDimensions - row) / yGridDimensions};
renderers[index]->SetViewport(viewport);
renderWindow->AddRenderer(renderers[index]);
}
}

vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
vtkSmartPointer<vtkInteractorStyleImage> style =
vtkSmartPointer<vtkInteractorStyleImage>::New();

renderWindowInteractor->SetInteractorStyle(style);
renderWindowInteractor->SetRenderWindow(renderWindow);

// Renderers share one camera
renderWindow->Render();
renderers[0]->GetActiveCamera()->Dolly(1.5);
renderers[0]->ResetCameraClippingRange();

for (size_t r = 1; r < renderers.size(); ++r)
{
renderers[r]->SetActiveCamera(renderers[0]->GetActiveCamera());
}
renderWindowInteractor->Initialize();
renderWindowInteractor->Start();

return EXIT_SUCCESS;
}
namespace
{
void AddShotNoise(vtkSmartPointer<vtkImageData> &inputImage,
vtkSmartPointer<vtkImageData> &outputImage,
double noiseAmplitude,
double noiseFraction,
int extent[6])
{
vtkSmartPointer<vtkImageNoiseSource> shotNoiseSource =
vtkSmartPointer<vtkImageNoiseSource>::New();
shotNoiseSource->SetWholeExtent(extent);
shotNoiseSource->SetMinimum(0.0);
shotNoiseSource->SetMaximum(1.0);

vtkSmartPointer<vtkImageThreshold> shotNoiseThresh1 =
vtkSmartPointer<vtkImageThreshold>::New();
shotNoiseThresh1->SetInputConnection(shotNoiseSource->GetOutputPort());
shotNoiseThresh1->ThresholdByLower(1.0 - noiseFraction);
shotNoiseThresh1->SetInValue(0);
shotNoiseThresh1->SetOutValue(noiseAmplitude);

vtkSmartPointer<vtkImageThreshold> shotNoiseThresh2 =
vtkSmartPointer<vtkImageThreshold>::New();
shotNoiseThresh2->SetInputConnection(shotNoiseSource->GetOutputPort());
shotNoiseThresh2->ThresholdByLower(noiseFraction);
shotNoiseThresh2->SetInValue(1.0 - noiseAmplitude);
shotNoiseThresh2->SetOutValue(0.0);

vtkSmartPointer<vtkImageMathematics> shotNoise =
vtkSmartPointer<vtkImageMathematics>::New();
shotNoise->SetInputConnection(0, shotNoiseThresh1->GetOutputPort());
shotNoise->SetInputConnection(1, shotNoiseThresh2->GetOutputPort());
shotNoise->SetOperationToAdd();

vtkSmartPointer<vtkImageMathematics> add =
vtkSmartPointer<vtkImageMathematics>::New();
add->SetInputData(0, inputImage);
add->SetInputConnection(1, shotNoise->GetOutputPort());
add->SetOperationToAdd();
add->Update();
outputImage->DeepCopy(add->GetOutput());
}
}

### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(HybridMedianComparison)

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

### Download and Build HybridMedianComparison¶

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

cd HybridMedianComparison/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:

./HybridMedianComparison

WINDOWS USERS

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