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.

You will need the following in your CMakeLists.txt file:

find_package(VTK
 COMPONENTS
    CommonCore
    CommonDataModel
    CommonExecutionModel
    FiltersSources
    InfovisCore
)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

ImageAlgorithmFilter.cxx

#include <vtkImageData.h>
#include <vtkNew.h>

#include "vtkImageAlgorithmFilter.h"

void PrintImage(vtkImageData* image);

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

  // Fill every entry of the image data with "2.0"
  const 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);

  vtkNew<vtkImageAlgorithmFilter> filter;
  filter->SetInputData(input);
  filter->Update();

  vtkImageData* output = filter->GetOutput();

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

  return 0;
}

void PrintImage(vtkImageData* image)
{
  const 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 <vtkDataObject.h>
#include <vtkImageData.h>
#include <vtkInformation.h>
#include <vtkInformationVector.h>
#include <vtkNew.h>
#include <vtkObjectFactory.h>
#include <vtkStreamingDemandDrivenPipeline.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()));

  vtkNew<vtkImageData> image;
  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 3.12 FATAL_ERROR)

project(ImageAlgorithmFilter)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageAlgorithmFilter: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
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}
)

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.