# [SOLVED] Copying Headers after performing operation

Hello! I am fairly new to using ITK. I am trying to use the markov random field filter for segmentation using this as an example. I presegmented the image using the kmeans example.

The problem I am having is that the header information is not properly being transferred to the resulting MRF filter nrrd file. The Kmeans label nrrd file has the correct information. I tried several things like get the meta data and supplying it to the writer, the internsityrescalar, and the mrffilter but it didn’t seem to actually do anything. I tried getting it from the labelReader using labelReader->GetMetaDataDictionary(); but that also didn’t seem to work. I am kind of stuck at this point.

Thanks for your help, hopefully the question was clear enough.

1 Like

Hello @thatguy14! Please share a minimal working example or the current status of your code so it can be reproduced. Doing so will increase the chances of getting help!

1 Like

I understand, it’s difficult since my code is disjointed at the moment and I can’t share my dataset. In any case here is how to run it (don’t know the correct process

1. Need attached image “Cropped Volume.nrrd” and segKmeans.nrrd
2. Compile MRF script below (from first link in first post)
3. run it using: SegmenterMRF.exe “Cropped volume.nrrd” segKmeans.nrrd segMRF.nrrd 2 2 4 0 50 100 150
4. Look at header information for the “segMRF.nrrd” and compare to other volumes (ex cropped volume.nrrd). It has the incorrect header information (space origin and directions).

Hopefully this is formatted okay. Again, new to all this

segKmeans.nrrd (844.1 KB)
Cropped volume.nrrd (949.8 KB)

/*=========================================================================
*

• you may not use this file except in compliance with the License.
• You may obtain a copy of the License at
•     http://www.apache.org/licenses/LICENSE-2.0.txt

• Unless required by applicable law or agreed to in writing, software
• WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
• See the License for the specific language governing permissions and

=========================================================================/
// Software Guide : BeginCommandLineArgs
// INPUTS: {BrainT1Slice.png}
// INPUTS: {BrainT1Slice_labelled.png}
// OUTPUTS: {ScalarImageMarkovRandomField1Output.png}
// ARGUMENTS: 50 3 3 14.8 91.6 134.9
// Software Guide : EndCommandLineArgs
// Software Guide : BeginLatex
//
// This example shows how to use the Markov Random Field approach for
// classifying the pixel of a scalar image.
//
// The \subdoxygen{Statistics}{MRFImageFilter} is used for refining an initial
// classification by introducing the spatial coherence of the labels. The user
// should provide two images as input. The first image is the one to be
// classified while the second image is an image of labels representing an
// initial classification.
//
// Software Guide : EndLatex
// Software Guide : BeginLatex
//
// The following headers are related to reading input images, writing the
// output image, and making the necessary conversions between scalar and vector
// images.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
#include “itkImage.h”
#include “itkImageFileWriter.h”
#include “itkComposeImageFilter.h”
// Software Guide : EndCodeSnippet
#include “itkRescaleIntensityImageFilter.h”
// Software Guide : BeginLatex
//
// The following headers are related to the statistical classification classes.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
#include “itkMRFImageFilter.h”
#include “itkDistanceToCentroidMembershipFunction.h”
#include “itkMinimumDecisionRule.h”
// Software Guide : EndCodeSnippet
int main(int argc, char * argv[])
{
if (argc < 7)
{
std::cerr << “Usage: " << std::endl;
std::cerr << argv[0];
std::cerr << " inputScalarImage inputLabeledImage”;
std::cerr << " outputLabeledImage numberOfIterations";
std::cerr << " smoothingFactor numberOfClasses";
std::cerr << " mean1 mean2 … meanN " << std::endl;
return EXIT_FAILURE;
}
const char * inputImageFileName = argv[1];
const char * inputLabelImageFileName = argv[2];
const char * outputImageFileName = argv[3];
const unsigned int numberOfIterations = atoi(argv[4]);
const double smoothingFactor = atof(argv[5]);
const unsigned int numberOfClasses = atoi(argv[6]);
constexpr unsigned int numberOfArgumentsBeforeMeans = 7;
if (static_cast(argc) <
numberOfClasses + numberOfArgumentsBeforeMeans)
{
std::cerr << "Error: " << std::endl;
std::cerr << numberOfClasses << " classes have been specified ";
std::cerr << "but not enough means have been provided in the command ";
std::cerr << "line arguments " << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// First we define the pixel type and dimension of the image that we intend to
// classify. With this image type we can also declare the
// set its input filename. In this particular case we choose to use
// \code{signed short} as pixel type, which is typical for MicroMRI and CT data
// sets.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using PixelType = signed short;
constexpr unsigned int Dimension = 3;
using ImageType = itk::Image<PixelType, Dimension >;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// As a second step we define the pixel type and dimension of the image of
// labels that provides the initial classification of the pixels from the first
// image. This initial labeled image can be the output of a K-Means method like
// the one illustrated in section \ref{sec:KMeansClassifier}.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using LabelPixelType = unsigned char;
using LabelImageType = itk::Image<LabelPixelType, Dimension >;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Since the Markov Random Field algorithm is defined in general for images
// whose pixels have multiple components, that is, images of vector type, we
// must adapt our scalar image in order to satisfy the interface expected by
// the \code{MRFImageFilter}. We do this by using the
// \doxygen{ComposeImageFilter}. With this filter we will present our
// scalar image as a vector image whose vector pixels contain a single
// component.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using ArrayPixelType = itk::FixedArray<LabelPixelType, 1>;
using ArrayImageType = itk::Image< ArrayPixelType, Dimension >;
using ScalarToArrayFilterType = itk::ComposeImageFilter<
ImageType, ArrayImageType >;
ScalarToArrayFilterType::Pointer
scalarToArrayFilter = ScalarToArrayFilterType::New();

std::cout << “Right Before the MRF filter” << std::endl;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// With the input image type \code{ImageType} and labeled image type
// \code{LabelImageType} we instantiate the type of the
// \doxygen{MRFImageFilter} that will apply the Markov Random Field algorithm
// in order to refine the pixel classification.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using MRFFilterType = itk::MRFImageFilter< ArrayImageType, LabelImageType >;
MRFFilterType::Pointer mrfFilter = MRFFilterType::New();
mrfFilter->SetInput(scalarToArrayFilter->GetOutput());
std::cout << “Right After the MRF filter” << std::endl;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We set now some of the parameters for the MRF filter. In particular, the
// number of classes to be used during the classification, the maximum number
// of iterations to be run in this filter and the error tolerance that will be
// used as a criterion for convergence.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
mrfFilter->SetNumberOfClasses(numberOfClasses);
mrfFilter->SetMaximumNumberOfIterations(numberOfIterations);
mrfFilter->SetErrorTolerance(1e-7);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The smoothing factor represents the tradeoff between fidelity to the
// observed image and the smoothness of the segmented image. Typical smoothing
// factors have values between 1~5. This factor will multiply the weights that
// define the influence of neighbors on the classification of a given pixel.
// The higher the value, the more uniform will be the regions resulting from
// the classification refinement.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
mrfFilter->SetSmoothingFactor(smoothingFactor);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Given that the MRF filter need to continually relabel the pixels, it needs
// access to a set of membership functions that will measure to what degree
// every pixel belongs to a particular class. The classification is performed
// by the \doxygen{ImageClassifierBase} class, that is instantiated using the
// type of the input vector image and the type of the labeled image.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using SupervisedClassifierType = itk::ImageClassifierBase<
ArrayImageType,
LabelImageType >;
SupervisedClassifierType::Pointer classifier =
SupervisedClassifierType::New();
std::cout << “Right After the classifierbase filter” << std::endl;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The classifier need a decision rule to be set by the user. Note that we must
// use \code{GetPointer()} in the call of the \code{SetDecisionRule()} method
// because we are passing a SmartPointer, and smart pointer cannot perform
// polymorphism, we must then extract the raw pointer that is associated to the
// smart pointer. This extraction is done with the GetPointer() method.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using DecisionRuleType = itk::Statistics::MinimumDecisionRule;
DecisionRuleType::Pointer classifierDecisionRule = DecisionRuleType::New();
classifier->SetDecisionRule(classifierDecisionRule);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We now instantiate the membership functions. In this case we use the
// \subdoxygen{Statistics}{DistanceToCentroidMembershipFunction} class
// templated over the pixel type of the vector image, that in our example
// happens to be a vector of dimension 1.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using MembershipFunctionType = itk::Statistics::DistanceToCentroidMembershipFunction;
using MembershipFunctionPointer = MembershipFunctionType::Pointer;
double meanDistance = 0;
MembershipFunctionType::CentroidType centroid(1);
for (unsigned int i = 0; i < numberOfClasses; i++)
{
MembershipFunctionPointer membershipFunction =
MembershipFunctionType::New();
centroid[0] = atof(argv[i + numberOfArgumentsBeforeMeans]);
membershipFunction->SetCentroid(centroid);
meanDistance += static_cast< double > (centroid[0]);
}
if (numberOfClasses > 0)
{
meanDistance /= numberOfClasses;
}
else
{
std::cerr << “ERROR: numberOfClasses is 0” << std::endl;
return EXIT_FAILURE;
}
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We set the Smoothing factor. This factor will multiply the weights that
// define the influence of neighbors on the classification of a given pixel.
// The higher the value, the more uniform will be the regions resulting from
// the classification refinement.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
mrfFilter->SetSmoothingFactor(smoothingFactor);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// and we set the neighborhood radius that will define the size of the clique
// to be used in the computation of the neighbors’ influence in the
// classification of any given pixel. Note that despite the fact that we call
// this a radius, it is actually the half size of an hypercube. That is, the
// actual region of influence will not be circular but rather an N-Dimensional
// box. For example, a neighborhood radius of 2 in a 3D image will result in a
// clique of size 5x5x5 pixels, and a radius of 1 will result in a clique of
// size 3x3x3 pixels.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We should now set the weights used for the neighbors. This is done by
// passing an array of values that contains the linear sequence of weights for
// the neighbors. For example, in a neighborhood of size 3x3x3, we should
// provide a linear array of 9 weight values. The values are packaged in a
// \code{std::vector} and are supposed to be \code{double}. The following lines
// illustrate a typical set of values for a 3x3x3 neighborhood. The array is
// arranged and then passed to the filter by using the method
// \code{SetMRFNeighborhoodWeight()}.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
std::cout << “Right After the Radius filter” << std::endl;
std::vector< double > weights;

//weights.push_back(1.5);
//weights.push_back(2.0);
//weights.push_back(1.5);
//weights.push_back(2.0);
//weights.push_back(0.0); // This is the central pixel
//weights.push_back(2.0);
//weights.push_back(1.5);
//weights.push_back(2.0);
//weights.push_back(1.5);

//As far as I understand it, it goes along the rows from the top or bottom slice upwards/downwards… The weights have to be the same size as the neighbourhood. For a 3d image with a radius of 1 (3x3x3) It needs 9x3 weights

weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.5);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);

weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);
weights.push_back(1.7);

weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.5);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
weights.push_back(1.3);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We now scale weights so that the smoothing function and the image fidelity
// functions have comparable value. This is necessary since the label
// image and the input image can have different dynamic ranges. The fidelity
// function is usually computed using a distance function, such as the
// \doxygen{DistanceToCentroidMembershipFunction} or one of the other
// membership functions. They tend to have values in the order of the means
// specified.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
double totalWeight = 0;
for (std::vector< double >::const_iterator wcIt = weights.begin();
wcIt != weights.end(); ++wcIt)
{
totalWeight += *wcIt;
}
for (double & weight : weights)
{
weight = static_cast< double > (weight * meanDistance / (2 * totalWeight));
}
mrfFilter->SetMRFNeighborhoodWeight(weights);
std::cout << “Right After the MRF weights” << std::endl;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Finally, the classifier class is connected to the Markof Random Fields filter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
mrfFilter->SetClassifier(classifier);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The output image produced by the \doxygen{MRFImageFilter} has the same pixel
// type as the labeled input image. In the following lines we use the
// \code{OutputImageType} in order to instantiate the type of a
// \doxygen{ImageFileWriter}. Then create one, and connect it to the output of
// the classification filter after passing it through an intensity rescaler
// to rescale it to an 8 bit dynamic range
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using OutputImageType = MRFFilterType::OutputImageType;
// Software Guide : EndCodeSnippet
// Rescale outputs to the dynamic range of the display
using RescaledOutputImageType = itk::Image< unsigned char, Dimension >;
OutputImageType, RescaledOutputImageType >;
intensityRescaler->SetOutputMinimum(0);
intensityRescaler->SetOutputMaximum(255);
intensityRescaler->SetInput(mrfFilter->GetOutput());
std::cout << “this is a test” << std::endl;
// Software Guide : BeginCodeSnippet
using WriterType = itk::ImageFileWriter< OutputImageType >;
WriterType::Pointer writer = WriterType::New();
writer->SetInput(intensityRescaler->GetOutput());
writer->SetFileName(outputImageFileName);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// We are now ready for triggering the execution of the pipeline. This is done
// by simply invoking the \code{Update()} method in the writer. This call will
// propagate the update request to the reader and then to the MRF filter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
try
{
writer->Update();
}
catch (itk::ExceptionObject & excp)
{
std::cerr << "Problem encountered while writing ";
std::cerr << " image file : " << argv[2] << std::endl;
std::cerr << excp << std::endl;
return EXIT_FAILURE;
}
// Software Guide : EndCodeSnippet
std::cout << "Number of Iterations : ";
std::cout << mrfFilter->GetNumberOfIterations() << std::endl;
std::cout << "Stop condition: " << std::endl;
std::cout << " (1) Maximum number of iterations " << std::endl;
std::cout << " (2) Error tolerance: " << std::endl;
std::cout << mrfFilter->GetStopCondition() << std::endl;
// Software Guide : BeginLatex
//
// \begin{figure} \center
// \includegraphics[width=0.44\textwidth]{ScalarImageMarkovRandomField1Output}
// \itkcaption[Output of the ScalarImageMarkovRandomField]{Effect of the
// MRF filter on a T1 slice of the brain.}
// \label{fig:ScalarImageMarkovRandomFieldInputOutput}
// \end{figure}
//
// Figure \ref{fig:ScalarImageMarkovRandomFieldInputOutput}
// illustrates the effect of this filter with three classes.
// In this example the filter was run with a smoothing factor of 3.
// The labeled image was produced by ScalarImageKmeansClassifier.cxx
// and the means were estimated by ScalarImageKmeansModelEstimator.cxx.
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}

1 Like

Thanks @thatguy14, you can use itk::ChangeInformationImageFilter to copy metadata from the input to the output.

  ...

intensityRescaler->SetOutputMaximum(255);
intensityRescaler->SetInput(mrfFilter->GetOutput());
std::cout << "this is a test" << std::endl;

using ChangeInformationFilterType = itk::ChangeInformationImageFilter<RescaledOutputImageType>;
ChangeInformationFilterType::Pointer changeInfo = ChangeInformationFilterType::New();
changeInfo->SetInput(intensityRescaler->GetOutput());
changeInfo->ChangeAll();
// Get metadata from input image, we need to update the reader first to access the image.
changeInfo->SetOutputSpacing(referenceImage->GetSpacing());
changeInfo->SetOutputOrigin(referenceImage->GetOrigin());
changeInfo->SetOutputDirection(referenceImage->GetDirection());

// Software Guide : BeginCodeSnippet
using WriterType = itk::ImageFileWriter< RescaledOutputImageType >;
WriterType::Pointer writer = WriterType::New();
writer->SetInput(changeInfo->GetOutput());
writer->SetFileName(outputImageFileName);
// Software Guide : EndCodeSnippet

...

2 Likes

@phcerdan Hi That did not seem to work for me. The Header still has ‘(1,0,0) (0,1,0) (0,0,1)’ for the space directions and ‘(0,0,0)’ for the spaceorigin.

@phcerdan Sorry nevermind made a mistake! I forgot to change the writer! Apologies for that. I don’t know if there is a way to mark solved but that has done the trick! Thanks very much

1 Like

@thatguy14 you are welcome, glad that it worked!