Variance

Measure allowing to compute variance of intensities for shape. More...

Classes
class	ipsdk::imaproc::shape::analysis::VarianceMsr
	Measurement object for measure Variance. More...
class	ipsdk::imaproc::shape::analysis::VarianceMsrInfo
	Information object for measure Variance. More...

Detailed Description

Measure allowing to compute variance of intensities for shape.

Variance measure computes the variance of image pixel/voxel intensity values associated to a 2d/3d shape.

For recall, the variance computed on a set of values equals to:

with the mean of

Here is an example of variance measurement in 2d case :

Author

H. Delestre

Date

2015/07/07

Copyright

2015 Reactiv'IP, all right reserved.

Measure allowing to compute variance of intensities for shape

Measure synthesis :

Measure Type	Measure Unit Type	Parameter Type	Result Type	Shape Requirements
Generic	None	None	Value (ipsdk::ipReal64)	Row Intersections

See Shape measurement for additional information on these pictograms

Measure Type :

This is a generic measure

• it does not directly use shape or image data
• it can use dependencies to other measures to compute a result (see Measure Dependencies section)

This measure can be used in 2d and 3d case

Measure Unit Type:

Measure Variance is not associated to any unit [ipsdk::shape::analysis::eMsrUnitFormat::eMUF_NoUnit]

Measure Parameter Type :

Measure Variance has no parameters

Measure Result Type :

Measure Variance is associated to ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64> results

Measure Shape Requirements :

Measure Variance requires row intersections from shape data

Measure Dependencies :

Measure Variance depends on following measures :

Measure Mode	Measure Name	Measure Type	Measure Parameters
eMVP_2d3d	SumSquare	SumSquare
eMVP_2d	NbPixels	NbPixels2d
eMVP_3d	NbPixels	NbPixels3d
eMVP_2d3d	Mean	Mean

Note

See Shape Analysis 2d for more information on general shape 2d analysis and measurement usage.

See Shape Analysis 3d for more information on general shape 3d analysis and measurement usage.

Example of Python code :

Generic example in 2d case :

import PyIPSDK
import PyIPSDK.IPSDKIPLShapeAnalysis as shapeanalysis

    # Create the infoset
    inMeasureInfoSet2d = PyIPSDK.createMeasureInfoSet2d()
    PyIPSDK.createMeasureInfo(inMeasureInfoSet2d, "VarianceMsr")
    
    #Perform the analysis
    outMeasureSet = shapeanalysis.labelAnalysis2d(inGreyImg, inLabelImg2d, inMeasureInfoSet2d)
    
    # save results to csv format
    PyIPSDK.saveCsvMeasureFile(os.path.join(tmpPath,  "shape_analysis_results.csv"), outMeasureSet)
    
    # retrieve measure results
    outMsr = outMeasureSet.getMeasure("VarianceMsr")
    
    # retrieve measure values
    outMsrValues = outMsr.getMeasureResult().getColl(0)
    print("First label measurement equal " + str(outMsrValues[1]))

Generic example in 3d case :

import PyIPSDK
import PyIPSDK.IPSDKIPLShapeAnalysis as shapeanalysis

    # Create the infoset
    inMeasureInfoSet3d = PyIPSDK.createMeasureInfoSet3d()
    PyIPSDK.createMeasureInfo(inMeasureInfoSet3d, "VarianceMsr")
    
    #Perform the analysis
    outMeasureSet = shapeanalysis.labelAnalysis3d(inGreyImg, inLabelImg, inMeasureInfoSet3d)
    
    # save results to csv format
    PyIPSDK.saveCsvMeasureFile(os.path.join(tmpPath,  "shape_analysis_results.csv"), outMeasureSet)
    
    # retrieve measure results
    outMsr = outMeasureSet.getMeasure("VarianceMsr")
    
    # retrieve measure values
    outMsrValues = outMsr.getMeasureResult().getColl(0)
    print("First label measurement equal " + str(outMsrValues[1]))

Example of C++ code :

Example informations

Associated library

IPSDKIPLShapeAnalysis

Code Example

    // opening grey level input image
    ImagePtr pInGreyImg2d = loadTiffImageFile(inputGreyImgPath);

    // read entity shape 2d collection used for processing
    Shape2dCollPtr pShape2dColl = boost::make_shared<Shape2dColl>();
    readFromXmlFile(inputShape2dCollPath, *pShape2dColl);

    // define a measure info set
    MeasureInfoSetPtr pMeasureInfoSet = MeasureInfoSet::create2dInstance();
    createMeasureInfo(pMeasureInfoSet, "VarianceMsr");

    // compute measure on shape 2d collection
    MeasureSetPtr pOutMeasureSet = shapeAnalysis2d(pInGreyImg2d, pShape2dColl, pMeasureInfoSet);

    // retrieve associated results
    const MeasureConstPtr& pVarianceOutMsr = pOutMeasureSet->getMeasure("VarianceMsr");
    const ValueMeasureResult<ipReal64>& outResults = static_cast<const ValueMeasureResult<ipReal64>&>(pVarianceOutMsr->getMeasureResult());