lsst::ip::diffim::detail::KernelPcaVisitor< PixelT > Class Template Reference

A class to run a PCA on all candidate kernels (represented as Images). More...

#include <KernelPca.h>

Inheritance diagram for lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >:

Public Types
typedef lsst::afw::image::Image < lsst::afw::math::Kernel::Pixel >	ImageT
typedef boost::shared_ptr < KernelPcaVisitor< PixelT > >	Ptr

Public Member Functions
	KernelPcaVisitor (boost::shared_ptr< KernelPca< ImageT > > imagePca)
virtual	~KernelPcaVisitor ()
lsst::afw::math::KernelList	getEigenKernels ()
void	processCandidate (lsst::afw::math::SpatialCellCandidate *candidate)
void	subtractMean ()
boost::shared_ptr< ImageT >	returnMean ()
Public Member Functions inherited from lsst::afw::math::CandidateVisitor
	CandidateVisitor ()
virtual	~CandidateVisitor ()
virtual void	reset ()

Private Attributes
boost::shared_ptr< KernelPca < ImageT > >	_imagePca
	Structure to fill with images. More...
boost::shared_ptr< ImageT >	_mean
	Mean image calculated before Pca. More...

Detailed Description

template<typename PixelT>
class lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >

A class to run a PCA on all candidate kernels (represented as Images).

Note

Templated on the pixel types of the MaskedImages it will be visiting (typically float).

Works in concert with a afwMath::SpatialCellSet and ip::Diffim KernelPca to create a Karhunen-Loeve basis from all the good KernelCandidates. This class adds the extra functionality to subtract off the mean kernel from all entries, which makes the resulting basis more compact. The user needs to manually add this mean image into the resulting basis list after imagePca.analyze() is called.

KernelPca (and base class afwImage::ImagePca) weight objects of different brightness differently. However we don't necessarily want images with larger kernel sums to have more weight. Each kernel should have constant weight in the Pca. For simplicity we scale them to have the same kernel sum, 1.0, and send to ImagePca that the flux (weight) is 1.0.

Definition at line 40 of file KernelPca.h.

Member Typedef Documentation

template<typename PixelT >

typedef lsst::afw::image::Image<lsst::afw::math::Kernel::Pixel> lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::ImageT

Definition at line 42 of file KernelPca.h.

template<typename PixelT >

typedef boost::shared_ptr<KernelPcaVisitor<PixelT> > lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::Ptr

Definition at line 43 of file KernelPca.h.

Constructor & Destructor Documentation

template<typename PixelT >

lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::KernelPcaVisitor

(

boost::shared_ptr< KernelPca< ImageT > >

imagePca

)

Parameters

imagePca

Set of Images to initialise

Definition at line 57 of file KernelPca.cc.

          :
        afwMath::CandidateVisitor(),
        _imagePca(imagePca),
        _mean() 
    {};

template<typename PixelT >

virtual lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::~KernelPcaVisitor ( )

inlinevirtual

Definition at line 46 of file KernelPca.h.

{};

Member Function Documentation

template<typename PixelT >

lsst::afw::math::KernelList lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::getEigenKernels

(

)

Definition at line 66 of file KernelPca.cc.

                                                                    {
        afwMath::KernelList kernelList;

        std::vector<typename ImageT::Ptr> eigenImages = _imagePca->getEigenImages();
        int ncomp = eigenImages.size();

        if (_mean) {
            kernelList.push_back(afwMath::Kernel::Ptr(
                                     new afwMath::FixedKernel(
                                         afwImage::Image<afwMath::Kernel::Pixel>
                                         (*_mean, true))));
        }
        for (int i = 0; i < ncomp; i++) {
            afwImage::Image<afwMath::Kernel::Pixel> img = 
                afwImage::Image<afwMath::Kernel::Pixel>(*eigenImages[i], true);
            kernelList.push_back(afwMath::Kernel::Ptr(
                                     new afwMath::FixedKernel(img)
                                     ));
        }

        return kernelList;
    }

template<typename PixelT >

void lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::processCandidate ( lsst::afw::math::SpatialCellCandidate *  candidate )

virtual

Reimplemented from lsst::afw::math::CandidateVisitor.

Definition at line 90 of file KernelPca.cc.

                                                                                              {
        
        KernelCandidate<PixelT> *kCandidate = dynamic_cast<KernelCandidate<PixelT> *>(candidate);
        if (kCandidate == NULL) {
            throw LSST_EXCEPT(pexExcept::LogicError,
                              "Failed to cast SpatialCellCandidate to KernelCandidate");
        }
        pexLogging::TTrace<6>("lsst.ip.diffim.SetPcaImageVisitor.processCandidate", 
                              "Processing candidate %d", kCandidate->getId());
        
        try {
            /* Normalize to unit sum */
            PTR(ImageT) kImage = kCandidate->getKernelSolution(
                KernelCandidate<PixelT>::ORIG)->makeKernelImage();
            *kImage           /= kCandidate->getKernelSolution(
                KernelCandidate<PixelT>::ORIG)->getKsum();
            /* Tell imagePca they have the same weighting in the Pca */
            _imagePca->addImage(kImage, 1.0);
        } catch(pexExcept::Exception &e) {
            return;
        }
    }

template<typename PixelT >

boost::shared_ptr< ImageT > lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::returnMean ( )

inline

Definition at line 51 of file KernelPca.h.

{return _mean;}

template<typename PixelT >

void lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::subtractMean

(

)

Definition at line 114 of file KernelPca.cc.

                                                {
        /* 
           If we don't subtract off the mean before we do the Pca, the
           subsequent terms carry less of the power than if you do subtract
           off the mean.  Explicit example:
           
           With mean subtraction:
             DEBUG: Eigenvalue 0 : 0.010953 (0.373870 %)
             DEBUG: Eigenvalue 1 : 0.007927 (0.270604 %)
             DEBUG: Eigenvalue 2 : 0.001393 (0.047542 %)
             DEBUG: Eigenvalue 3 : 0.001092 (0.037261 %)
             DEBUG: Eigenvalue 4 : 0.000829 (0.028283 %)
           
           Without mean subtraction:
             DEBUG: Eigenvalue 0 : 0.168627 (0.876046 %)
             DEBUG: Eigenvalue 1 : 0.007935 (0.041223 %)
             DEBUG: Eigenvalue 2 : 0.006049 (0.031424 %)
             DEBUG: Eigenvalue 3 : 0.001188 (0.006173 %)
             DEBUG: Eigenvalue 4 : 0.001050 (0.005452 %)

           After the first term above, which basically represents the mean,
           the remaining terms carry less of the power than if you do
           subtract off the mean.  (0.041223/(1-0.876046) < 0.373870).
         */
        pexLogging::TTrace<6>("lsst.ip.diffim.KernelPcaVisitor.subtractMean", 
                              "Subtracting mean feature before Pca");
        
        _mean = _imagePca->getMean();
        KernelPca<ImageT>::ImageList imageList = _imagePca->getImageList();
        for (typename KernelPca<ImageT>::ImageList::const_iterator ptr = imageList.begin(), 
                 end = imageList.end(); ptr != end; ++ptr) {
            **ptr -= *_mean;
        }
    }

Member Data Documentation

template<typename PixelT >

boost::shared_ptr<KernelPca<ImageT> > lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::_imagePca

private

Structure to fill with images.

Definition at line 53 of file KernelPca.h.

template<typename PixelT >

boost::shared_ptr< ImageT > lsst::ip::diffim::detail::KernelPcaVisitor< PixelT >::_mean

private

Mean image calculated before Pca.

Definition at line 54 of file KernelPca.h.

---

The documentation for this class was generated from the following files:

• /home/lsstsw/stack/Linux64/ip_diffim/11.0+1/include/lsst/ip/diffim/KernelPca.h
• /home/lsstsw/stack/Linux64/ip_diffim/11.0+1/src/KernelPca.cc