Mask Image#

Synopsis#

Apply a mask to an image.

Results#

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"

#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkMaskImageFilter.h"
#include "itkImageRegionIteratorWithIndex.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;
  }

  const auto input = itk::ReadImage<ImageType>(argv[1]);

  auto mask = ImageType::New();
  CreateHalfMask(input, mask);

  using MaskFilterType = itk::MaskImageFilter<ImageType, ImageType>;
  auto maskFilter = MaskFilterType::New();
  maskFilter->SetInput(input);
  maskFilter->SetMaskImage(mask);
  mask->Print(std::cout);
#ifdef ENABLE_QUICKVIEW
  QuickView viewer;
  viewer.AddImage(input.GetPointer(), 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::ImageRegionIteratorWithIndex<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;
  }
}

Classes demonstrated#

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

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.