Mask Image

Synopsis

Apply a mask to an image.

Results

Input Image

Output In VTK Window

Output:

Image (0x7f9d9c95ccc0)
RTTI typeinfo:   itk::Image<unsigned char, 2u>
Reference Count: 2
Modified Time: 235
Debug: Off
Object Name:
Observers:
  none
Source: (none)
Source output name: (none)
Release Data: Off
Data Released: False
Global Release Data: Off
PipelineMTime: 0
UpdateMTime: 0
RealTimeStamp: 0 seconds
LargestPossibleRegion:
  Dimension: 2
  Index: [0, 0]
  Size: [512, 342]
BufferedRegion:
  Dimension: 2
  Index: [0, 0]
  Size: [512, 342]
RequestedRegion:
  Dimension: 2
  Index: [0, 0]
  Size: [512, 342]
Spacing: [1, 1]
Origin: [0, 0]
Direction:
1 0
0 1

IndexToPointMatrix:
1 0
0 1

PointToIndexMatrix:
1 0
0 1

Inverse Direction:
1 0
0 1

PixelContainer:
  ImportImageContainer (0x7f9d9c95d000)
    RTTI typeinfo:   itk::ImportImageContainer<unsigned long, unsigned char>
    Reference Count: 1
    Modified Time: 236
    Debug: Off
    Object Name:
    Observers:
      none
    Pointer: 0x7f9d90050000
    Container manages memory: true
    Size: 175104
    Capacity: 175104

Code

C++

#include "itkConfigure.h"

#if (ITK_VERSION_MAJOR < 4) // These are all defaults in ITKv4
//  Not supported in ITKv3.
int
main(int argc, char * argv[])
{
  return 0;
}
#else
#  include "itkImage.h"
#  include "itkImageFileReader.h"
#  include "itkMaskImageFilter.h"
#  include "itkImageRegionIterator.h"
#  ifdef ENABLE_QUICKVIEW
#    include "QuickView.h"
#  endif

using ImageType = itk::Image<unsigned char, 2>;

void
CreateHalfMask(ImageType::Pointer image, ImageType::Pointer & mask);

int
main(int argc, char * argv[])
{
  if (argc < 2)
  {
    std::cerr << "Usage: " << argv[0] << " filename" << std::endl;
    return EXIT_FAILURE;
  }

  using ReaderType = itk::ImageFileReader<ImageType>;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName(argv[1]);
  reader->Update();

  ImageType::Pointer mask = ImageType::New();
  CreateHalfMask(reader->GetOutput(), mask);

  using MaskFilterType = itk::MaskImageFilter<ImageType, ImageType>;
  MaskFilterType::Pointer maskFilter = MaskFilterType::New();
  maskFilter->SetInput(reader->GetOutput());
  maskFilter->SetMaskImage(mask);
  mask->Print(std::cout);
#  ifdef ENABLE_QUICKVIEW
  QuickView viewer;
  viewer.AddImage(reader->GetOutput(), true, itksys::SystemTools::GetFilenameName(argv[1]));

  std::stringstream desc;
  desc << "Mask";
  viewer.AddImage(mask.GetPointer(), true, desc.str());

  std::stringstream desc2;
  desc2 << "MaskFilter";
  viewer.AddImage(maskFilter->GetOutput(), true, desc2.str());

  viewer.Visualize();
#  endif
  return EXIT_SUCCESS;
}


void
CreateHalfMask(ImageType::Pointer image, ImageType::Pointer & mask)
{
  ImageType::RegionType region = image->GetLargestPossibleRegion();

  mask->SetRegions(region);
  mask->Allocate();

  ImageType::SizeType regionSize = region.GetSize();

  itk::ImageRegionIterator<ImageType> imageIterator(mask, region);

  // Make the left half of the mask white and the right half black
  while (!imageIterator.IsAtEnd())
  {
    if (imageIterator.GetIndex()[0] > static_cast<ImageType::IndexValueType>(regionSize[0]) / 2)
    {
      imageIterator.Set(0);
    }
    else
    {
      imageIterator.Set(255);
    }

    ++imageIterator;
  }
}
#endif

Classes demonstrated

template<typename TInputImage, typename TMaskImage, typename TOutputImage = TInputImage>
class MaskImageFilter : public itk::BinaryGeneratorImageFilter<TInputImage, TMaskImage, TOutputImage>

Mask an image with a mask.

This class is templated over the types of the input image type, the mask image type and the type of the output image. Numeric conversions (castings) are done by the C++ defaults.

The pixel type of the input 2 image must have a valid definition of the operator != with zero. This condition is required because internally this filter will perform the operation

if pixel_from_mask_image != masking_value
     pixel_output_image = pixel_input_image
else
     pixel_output_image = outside_value

The pixel from the input 1 is cast to the pixel type of the output image.

Note that the input and the mask images must be of the same size.

Warning

Any pixel value other than masking value (0 by default) will not be masked out.

See

MaskNegatedImageFilter

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Mask Image

See itk::MaskImageFilter for additional documentation.