ImageAlgorithmFilter

vtk-examples/Cxx/Developers/ImageAlgorithmFilter

Description¶

This example demonstrates how to setup the pipeline for a {{class vtkImageAlgorithm}} filter that takes a {{class vtkImageData}} as input and produces another vtkImageData as output. This particular example creates a 2x2 image and fills it with "2"s. The filter changes the (0,0) element to a 5.

Question

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Code¶

ImageAlgorithmFilter.cxx

#include <vtkSmartPointer.h>

#include "vtkImageAlgorithmFilter.h"
#include <vtkImageData.h>

void PrintImage(vtkImageData* image);

int main (int /* argc */, char * /* argv */ [])
{
  vtkSmartPointer<vtkImageData> input =
    vtkSmartPointer<vtkImageData>::New();
  // Setup the image
  input->SetDimensions(2,2,1);
  input->AllocateScalars(VTK_DOUBLE,1);

  // Fill every entry of the image data with "2.0"
  int* dims = input->GetDimensions();

  for (int y=0; y<dims[1]; y++)
  {
    for (int x=0; x<dims[0]; x++)
    {
      input->SetScalarComponentFromDouble(x,y,0,0,2.0);
    }
  }

  std::cout << "Input image: " << std::endl;
  PrintImage(input);

  vtkSmartPointer<vtkImageAlgorithmFilter> filter =
    vtkSmartPointer<vtkImageAlgorithmFilter>::New();
  filter->SetInputData(input);
  filter->Update();

  vtkImageData* output = filter->GetOutput();

  std::cout << "Output image: " << std::endl;
  PrintImage(output);

  return 0;
}

void PrintImage(vtkImageData* image)
{
  int* dims = image->GetDimensions();

  for (int y=0; y<dims[1]; y++)
  {
    for (int x=0; x<dims[0]; x++)
    {
      double v = image->GetScalarComponentAsDouble(x,y,0,0);
      std::cout << v << " ";
    }
    std::cout << std::endl;
  }
}

vtkImageAlgorithmFilter.h

#ifndef __vtkImageAlgorithmFilter_h
#define __vtkImageAlgorithmFilter_h

#include <vtkImageAlgorithm.h>

class vtkImageAlgorithmFilter : public vtkImageAlgorithm 
{
public:
  static vtkImageAlgorithmFilter *New();
  vtkTypeMacro(vtkImageAlgorithmFilter,vtkImageAlgorithm);

  vtkImageAlgorithmFilter(){}

protected:

  int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *) override;

private:
  vtkImageAlgorithmFilter(const vtkImageAlgorithmFilter&);  // Not implemented.
  void operator=(const vtkImageAlgorithmFilter&);  // Not implemented.
};

#endif

vtkImageAlgorithmFilter.cxx

#include "vtkImageAlgorithmFilter.h"

#include <vtkImageData.h>
#include <vtkObjectFactory.h>
#include <vtkStreamingDemandDrivenPipeline.h>
#include <vtkInformationVector.h>
#include <vtkInformation.h>
#include <vtkDataObject.h>
#include <vtkSmartPointer.h>

vtkStandardNewMacro(vtkImageAlgorithmFilter);

int vtkImageAlgorithmFilter::RequestData(vtkInformation *vtkNotUsed(request),
                                             vtkInformationVector **inputVector,
                                             vtkInformationVector *outputVector)
{
  // Get the info objects
  vtkInformation *inInfo = inputVector[0]->GetInformationObject(0);
  vtkInformation *outInfo = outputVector->GetInformationObject(0);

  // Get the input and ouptut
  vtkImageData *input = dynamic_cast<vtkImageData*>(
      inInfo->Get(vtkDataObject::DATA_OBJECT()));

  vtkImageData *output = dynamic_cast<vtkImageData*>(
      outInfo->Get(vtkDataObject::DATA_OBJECT()));

  vtkSmartPointer<vtkImageData> image =
    vtkSmartPointer<vtkImageData>::New();
  image->ShallowCopy(input);

  image->SetScalarComponentFromDouble(0,0,0,0, 5.0);

  output->ShallowCopy(image);

  // Without these lines, the output will appear real but will not work as the input to any other filters
  int extent[6];
  input->GetExtent(extent);
  output->SetExtent(extent);
  outInfo->Set(vtkStreamingDemandDrivenPipeline::UPDATE_EXTENT(),
               extent,
               6);
  outInfo->Set(vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT(),
               extent,
               6);
  return 1;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ImageAlgorithmFilter)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping ImageAlgorithmFilter: ${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(ImageAlgorithmFilter MACOSX_BUNDLE ImageAlgorithmFilter.cxx )
  target_link_libraries(ImageAlgorithmFilter PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ImageAlgorithmFilter MACOSX_BUNDLE ImageAlgorithmFilter.cxx )
  target_link_libraries(ImageAlgorithmFilter PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ImageAlgorithmFilter
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ImageAlgorithmFilter¶

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

cd ImageAlgorithmFilter/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:

./ImageAlgorithmFilter

WINDOWS USERS

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