Compute, for a given orientation, Feret diameter (measure based on polygonal approximation)

The 2d Feret diameter (also called "caliper diameter", referring to the measurement of an object size with a caliper) is a measure of the size of a 2d shape in a given direction (that will be noted $\theta$ within this document). It is equivalent to compute the width of the thinnest band of direction $\theta+\pi/2$ , containing the whole 2d shape. The orientation $\theta$ of the Feret diameter can be specified by the user, and must belong to the range [0; $\pi$ [.

Note

measuring the 2d Feret diameter of a shape with $\theta=0$ is equivalent to measure the x-size of the axis-aligned bounding box of the shape
measuring the 2d Feret diameter of a shape with $\theta=\pi/2$ is equivalent to measure the y-size of the axis-aligned bounding box of the shape

Here is an example of 2d Feret diameter measurement for $\theta=\pi/3$ :

computes, for a given orientation, Feret diameter

Measure synthesis :

Measure Type	Measure Unit Type	Parameter Type	Result Type	Shape Requirements
Generic	Length	FeretDiameter2dMsrParams	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, "FeretDiameter2dMsr")
    
    #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("FeretDiameter2dMsr")
    
    # 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, "FeretDiameter2dMsr", createFeretDiameter2dMsrParams(orientation));
    
    // compute measure on shape 2d collection
    MeasureSetPtr pOutMeasureSet = shapeAnalysis2d(pInGreyImg2d, pShape2dColl, pMeasureInfoSet);
    // retrieve associated results
    const MeasureConstPtr& pFeretDiameter2dOutMsr = pOutMeasureSet->getMeasure("FeretDiameter2dMsr");
    const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>& outResults = static_cast<const ipsdk::shape::analysis::ValueMeasureResult<ipsdk::ipReal64>&>(pFeretDiameter2dOutMsr->getMeasureResult());