Computes the distance between Hu moments of shapes in an image and and a template's Hu moments.

This measure computes the distance between the Hu moment invariants of a reference shape and the Hu invariants of each shape. Three distances are available:

$\begin{eqnarray*} d_1(A, B) & = & \sum_{i = 1}^{7}{\left| \frac{1}{m_i^A} - \frac{1}{m_i^B} \right|}\\ d_2(A, B) & = & \sum_{i = 1}^{7}{\left| m_i^A - m_i^B \right|}\\ d_3(A, B) & = & \max_{i = 1}^{7}{\frac{\left| m_i^A - m_i^B \right|}{\left| m_i^A \right|}} \end{eqnarray*}$

These distances are also used by the openCV matchShapes function (http://docs.opencv.org/2.4.13.2/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#matchshapes).

Here is an example of Hu moments distance measurement in 2d case with the distance type $d_3$ and without processing holes :

Measure synthesis :

Measure Type	Measure Unit Type	Parameter Type	Result Type	Shape Requirements
Geometry 2d	None	HuDistance2dMsrParams	Value (ipsdk::ipReal64)	Boundary Approximation

See Shape measurement for additional information on these pictograms

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, "HuDistance2dMsr")
    
    #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("HuDistance2dMsr")
    
    # 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>();
    IPSDK_REQUIRE(readFromXmlFile(inputShape2dCollPath, *pShape2dColl) == true);
    // For the example, the reference shape is the first shape in the input image
    Shape2dPtr pRefShape2d = pShape2dColl->getColl()[1];
    // define a measure info set
    MeasureInfoSetPtr pMeasureInfoSet = MeasureInfoSet::create2dInstance();
    createMeasureInfo(pMeasureInfoSet, "HuDistance2dMsr", createHuDistance2dMsrParams(*pRefShape2d, bProcessHoles, distType));
    
    // compute measure on shape 2d collection
    MeasureSetPtr pOutMeasureSet = shapeAnalysis2d(pInGreyImg2d, pShape2dColl, pMeasureInfoSet);
    // retrieve associated results
    const MeasureConstPtr& pHuDistance2dOutMsr = pOutMeasureSet->getMeasure("HuDistance2dMsr");
    const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>& outResults = static_cast<const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>&>(pHuDistance2dOutMsr->getMeasureResult());