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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkLabelVotingImageFilter_h
#define itkLabelVotingImageFilter_h
#include "itkImageToImageFilter.h"
namespace itk
{
/**
* \class LabelVotingImageFilter
*
* \brief This filter performs pixelwise voting among an arbitrary number
* of input images, where each of them represents a segmentation of the same
* scene (i.e., image).
*
* Label voting is a simple method of classifier combination applied to
* image segmentation. Typically, the accuracy of the combined segmentation
* exceeds the accuracy of any of the input segmentations. Voting is therefore
* commonly used as a way of boosting segmentation performance.
*
* The use of label voting for combination of multiple segmentations is
* described in
*
* T. Rohlfing and C. R. Maurer, Jr., "Multi-classifier framework for
* atlas-based image segmentation," Pattern Recognition Letters, 2005.
*
* \par INPUTS
* All input volumes to this filter must be segmentations of an image,
* that is, they must have discrete pixel values where each value represents
* a different segmented object.
*
* Input volumes must all contain the same size RequestedRegions. Not all
* input images must contain all possible labels, but all label values must
* have the same meaning in all images.
*
* \par OUTPUTS
* The voting filter produces a single output volume. Each output pixel
* contains the label that occurred most often among the labels assigned to
* this pixel in all the input volumes, that is, the label that received the
* maximum number of "votes" from the input pixels.. If the maximum number of
* votes is not unique, i.e., if more than one label have a maximum number of
* votes, an "undecided" label is assigned to that output pixel.
*
* By default, the label used for undecided pixels is the maximum label value
* used in the input images plus one. Since it is possible for an image with
* 8 bit pixel values to use all 256 possible label values, it is permissible
* to combine 8 bit (i.e., byte) images into a 16 bit (i.e., short) output
* image.
*
* \par PARAMETERS
* The label used for "undecided" labels can be set using
* SetLabelForUndecidedPixels. This functionality can be unset by calling
* UnsetLabelForUndecidedPixels.
*
* \author Torsten Rohlfing, SRI International, Neuroscience Program
*
* \ingroup ITKLabelVoting
*/
template <typename TInputImage, typename TOutputImage = TInputImage>
class ITK_TEMPLATE_EXPORT LabelVotingImageFilter : public ImageToImageFilter<TInputImage, TOutputImage>
{
public:
ITK_DISALLOW_COPY_AND_MOVE(LabelVotingImageFilter);
/** Standard class type aliases. */
using Self = LabelVotingImageFilter;
using Superclass = ImageToImageFilter<TInputImage, TOutputImage>;
using Pointer = SmartPointer<Self>;
using ConstPointer = SmartPointer<const Self>;
/** Method for creation through the object factory. */
itkNewMacro(Self);
/** \see LightObject::GetNameOfClass() */
itkOverrideGetNameOfClassMacro(LabelVotingImageFilter);
/** Extract some information from the image types. Dimensionality
* of the two images is assumed to be the same. */
using OutputPixelType = typename TOutputImage::PixelType;
using InputPixelType = typename TInputImage::PixelType;
/** Extract some information from the image types. Dimensionality
* of the two images is assumed to be the same. */
static constexpr unsigned int InputImageDimension = TInputImage::ImageDimension;
static constexpr unsigned int ImageDimension = TOutputImage::ImageDimension;
/** Image type alias support */
using InputImageType = TInputImage;
using OutputImageType = TOutputImage;
using InputImagePointer = typename InputImageType::ConstPointer;
using OutputImagePointer = typename OutputImageType::Pointer;
using LabelCountType = unsigned long;
/** Superclass type alias. */
using typename Superclass::OutputImageRegionType;
/** Set label value for undecided pixels. */
void
SetLabelForUndecidedPixels(const OutputPixelType l)
{
this->m_LabelForUndecidedPixels = l;
this->m_HasLabelForUndecidedPixels = true;
this->Modified();
}
/** Get label value used for undecided pixels.
* After updating the filter, this function returns the actual label value
* used for undecided pixels in the current output. Note that this value
* is overwritten when SetLabelForUndecidedPixels is called and the new
* value only becomes effective upon the next filter update.
*/
OutputPixelType
GetLabelForUndecidedPixels() const
{
return this->m_LabelForUndecidedPixels;
}
/** Unset label value for undecided pixels and turn on automatic selection.
*/
void
UnsetLabelForUndecidedPixels()
{
if (this->m_HasLabelForUndecidedPixels)
{
this->m_HasLabelForUndecidedPixels = false;
this->Modified();
}
}
#ifdef ITK_USE_CONCEPT_CHECKING
// Begin concept checking
itkConceptMacro(InputConvertibleToOutputCheck, (Concept::Convertible<InputPixelType, OutputPixelType>));
itkConceptMacro(IntConvertibleToInputCheck, (Concept::Convertible<int, InputPixelType>));
itkConceptMacro(SameDimensionCheck, (Concept::SameDimension<InputImageDimension, ImageDimension>));
itkConceptMacro(InputUnsignedIntCheck, (Concept::IsUnsignedInteger<InputPixelType>));
itkConceptMacro(IntConvertibleToOutputPixelType, (Concept::Convertible<int, OutputPixelType>));
itkConceptMacro(InputPlusIntCheck, (Concept::AdditiveOperators<InputPixelType, int>));
itkConceptMacro(InputIncrementDecrementOperatorsCheck, (Concept::IncrementDecrementOperators<InputPixelType>));
itkConceptMacro(OutputOStreamWritableCheck, (Concept::OStreamWritable<OutputPixelType>));
// End concept checking
#endif
protected:
LabelVotingImageFilter();
~LabelVotingImageFilter() override = default;
/** Determine maximum label value in all input images and initialize
* global data. */
void
BeforeThreadedGenerateData() override;
void
DynamicThreadedGenerateData(const OutputImageRegionType & outputRegionForThread) override;
void
PrintSelf(std::ostream &, Indent) const override;
/** Determine maximum value among all input images' pixels. */
InputPixelType
ComputeMaximumInputValue();
private:
OutputPixelType m_LabelForUndecidedPixels{};
bool m_HasLabelForUndecidedPixels{ false };
size_t m_TotalLabelCount{ 0 };
};
} // end namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
# include "itkLabelVotingImageFilter.hxx"
#endif
#endif
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