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232 lines
10 KiB
ReStructuredText
232 lines
10 KiB
ReStructuredText
Shape Distance and Common Interfaces
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====================================
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.. highlight:: cpp
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Shape Distance algorithms in OpenCV are derivated from a common interface that allows you to
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switch between them in a practical way for solving the same problem with different methods.
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Thus, all objects that implement shape distance measures inherit the
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:ocv:class:`ShapeDistanceExtractor` interface.
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ShapeDistanceExtractor
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----------------------
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.. ocv:class:: ShapeDistanceExtractor : public Algorithm
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Abstract base class for shape distance algorithms. ::
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class CV_EXPORTS_W ShapeDistanceExtractor : public Algorithm
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{
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public:
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CV_WRAP virtual float computeDistance(InputArray contour1, InputArray contour2) = 0;
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};
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ShapeDistanceExtractor::computeDistance
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---------------------------------------
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Compute the shape distance between two shapes defined by its contours.
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.. ocv:function:: float ShapeDistanceExtractor::computeDistance( InputArray contour1, InputArray contour2 )
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:param contour1: Contour defining first shape.
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:param contour2: Contour defining second shape.
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ShapeContextDistanceExtractor
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-----------------------------
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.. ocv:class:: ShapeContextDistanceExtractor : public ShapeDistanceExtractor
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Implementation of the Shape Context descriptor and matching algorithm proposed by Belongie et al. in
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"Shape Matching and Object Recognition Using Shape Contexts" (PAMI 2002).
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This implementation is packaged in a generic scheme, in order to allow you the implementation of the
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common variations of the original pipeline. ::
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class CV_EXPORTS_W ShapeContextDistanceExtractor : public ShapeDistanceExtractor
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{
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public:
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CV_WRAP virtual void setAngularBins(int nAngularBins) = 0;
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CV_WRAP virtual int getAngularBins() const = 0;
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CV_WRAP virtual void setRadialBins(int nRadialBins) = 0;
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CV_WRAP virtual int getRadialBins() const = 0;
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CV_WRAP virtual void setInnerRadius(float innerRadius) = 0;
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CV_WRAP virtual float getInnerRadius() const = 0;
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CV_WRAP virtual void setOuterRadius(float outerRadius) = 0;
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CV_WRAP virtual float getOuterRadius() const = 0;
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CV_WRAP virtual void setRotationInvariant(bool rotationInvariant) = 0;
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CV_WRAP virtual bool getRotationInvariant() const = 0;
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CV_WRAP virtual void setShapeContextWeight(float shapeContextWeight) = 0;
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CV_WRAP virtual float getShapeContextWeight() const = 0;
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CV_WRAP virtual void setImageAppearanceWeight(float imageAppearanceWeight) = 0;
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CV_WRAP virtual float getImageAppearanceWeight() const = 0;
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CV_WRAP virtual void setBendingEnergyWeight(float bendingEnergyWeight) = 0;
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CV_WRAP virtual float getBendingEnergyWeight() const = 0;
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CV_WRAP virtual void setImages(InputArray image1, InputArray image2) = 0;
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CV_WRAP virtual void getImages(OutputArray image1, OutputArray image2) const = 0;
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CV_WRAP virtual void setIterations(int iterations) = 0;
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CV_WRAP virtual int getIterations() const = 0;
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CV_WRAP virtual void setCostExtractor(Ptr<HistogramCostExtractor> comparer) = 0;
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CV_WRAP virtual Ptr<HistogramCostExtractor> getCostExtractor() const = 0;
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CV_WRAP virtual void setTransformAlgorithm(Ptr<ShapeTransformer> transformer) = 0;
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CV_WRAP virtual Ptr<ShapeTransformer> getTransformAlgorithm() const = 0;
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};
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/* Complete constructor */
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CV_EXPORTS_W Ptr<ShapeContextDistanceExtractor>
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createShapeContextDistanceExtractor(int nAngularBins=12, int nRadialBins=4,
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float innerRadius=0.2, float outerRadius=2, int iterations=3,
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const Ptr<HistogramCostExtractor> &comparer = createChiHistogramCostExtractor(),
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const Ptr<ShapeTransformer> &transformer = createThinPlateSplineShapeTransformer());
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ShapeContextDistanceExtractor::setAngularBins
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---------------------------------------------
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Establish the number of angular bins for the Shape Context Descriptor used in the shape matching pipeline.
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.. ocv:function:: void setAngularBins( int nAngularBins )
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:param nAngularBins: The number of angular bins in the shape context descriptor.
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ShapeContextDistanceExtractor::setRadialBins
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--------------------------------------------
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Establish the number of radial bins for the Shape Context Descriptor used in the shape matching pipeline.
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.. ocv:function:: void setRadialBins( int nRadialBins )
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:param nRadialBins: The number of radial bins in the shape context descriptor.
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ShapeContextDistanceExtractor::setInnerRadius
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---------------------------------------------
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Set the inner radius of the shape context descriptor.
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.. ocv:function:: void setInnerRadius(float innerRadius)
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:param innerRadius: The value of the inner radius.
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ShapeContextDistanceExtractor::setOuterRadius
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---------------------------------------------
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Set the outer radius of the shape context descriptor.
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.. ocv:function:: void setOuterRadius(float outerRadius)
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:param outerRadius: The value of the outer radius.
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ShapeContextDistanceExtractor::setShapeContextWeight
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----------------------------------------------------
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Set the weight of the shape context distance in the final value of the shape distance.
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The shape context distance between two shapes is defined as the symmetric sum of shape
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context matching costs over best matching points.
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The final value of the shape distance is a user-defined linear combination of the shape
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context distance, an image appearance distance, and a bending energy.
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.. ocv:function:: void setShapeContextWeight( float shapeContextWeight )
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:param shapeContextWeight: The weight of the shape context distance in the final distance value.
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ShapeContextDistanceExtractor::setImageAppearanceWeight
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-------------------------------------------------------
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Set the weight of the Image Appearance cost in the final value of the shape distance.
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The image appearance cost is defined as the sum of squared brightness differences in
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Gaussian windows around corresponding image points.
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The final value of the shape distance is a user-defined linear combination of the shape
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context distance, an image appearance distance, and a bending energy.
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If this value is set to a number different from 0, is mandatory to set the images that
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correspond to each shape.
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.. ocv:function:: void setImageAppearanceWeight( float imageAppearanceWeight )
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:param imageAppearanceWeight: The weight of the appearance cost in the final distance value.
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ShapeContextDistanceExtractor::setBendingEnergyWeight
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-----------------------------------------------------
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Set the weight of the Bending Energy in the final value of the shape distance.
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The bending energy definition depends on what transformation is being used to align the
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shapes.
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The final value of the shape distance is a user-defined linear combination of the shape
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context distance, an image appearance distance, and a bending energy.
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.. ocv:function:: void setBendingEnergyWeight( float bendingEnergyWeight )
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:param bendingEnergyWeight: The weight of the Bending Energy in the final distance value.
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ShapeContextDistanceExtractor::setImages
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----------------------------------------
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Set the images that correspond to each shape. This images are used in the calculation of the
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Image Appearance cost.
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.. ocv:function:: void setImages( InputArray image1, InputArray image2 )
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:param image1: Image corresponding to the shape defined by ``contours1``.
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:param image2: Image corresponding to the shape defined by ``contours2``.
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ShapeContextDistanceExtractor::setCostExtractor
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-----------------------------------------------
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Set the algorithm used for building the shape context descriptor cost matrix.
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.. ocv:function:: void setCostExtractor( Ptr<HistogramCostExtractor> comparer )
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:param comparer: Smart pointer to a HistogramCostExtractor, an algorithm that defines the cost matrix between descriptors.
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ShapeContextDistanceExtractor::setStdDev
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----------------------------------------
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Set the value of the standard deviation for the Gaussian window for the image appearance cost.
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.. ocv:function:: void setStdDev( float sigma )
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:param sigma: Standard Deviation.
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ShapeContextDistanceExtractor::setTransformAlgorithm
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----------------------------------------------------
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Set the algorithm used for aligning the shapes.
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.. ocv:function:: void setTransformAlgorithm( Ptr<ShapeTransformer> transformer )
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:param comparer: Smart pointer to a ShapeTransformer, an algorithm that defines the aligning transformation.
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HausdorffDistanceExtractor
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--------------------------
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.. ocv:class:: HausdorffDistanceExtractor : public ShapeDistanceExtractor
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A simple Hausdorff distance measure between shapes defined by contours,
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according to the paper "Comparing Images using the Hausdorff distance." by
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D.P. Huttenlocher, G.A. Klanderman, and W.J. Rucklidge. (PAMI 1993). ::
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class CV_EXPORTS_W HausdorffDistanceExtractor : public ShapeDistanceExtractor
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{
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public:
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CV_WRAP virtual void setDistanceFlag(int distanceFlag) = 0;
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CV_WRAP virtual int getDistanceFlag() const = 0;
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CV_WRAP virtual void setRankProportion(float rankProportion) = 0;
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CV_WRAP virtual float getRankProportion() const = 0;
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};
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/* Constructor */
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CV_EXPORTS_W Ptr<HausdorffDistanceExtractor> createHausdorffDistanceExtractor(int distanceFlag=cv::NORM_L2, float rankProp=0.6);
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HausdorffDistanceExtractor::setDistanceFlag
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-------------------------------------------
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Set the norm used to compute the Hausdorff value between two shapes. It can be L1 or L2 norm.
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.. ocv:function:: void setDistanceFlag( int distanceFlag )
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:param distanceFlag: Flag indicating which norm is used to compute the Hausdorff distance (NORM_L1, NORM_L2).
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HausdorffDistanceExtractor::setRankProportion
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---------------------------------------------
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This method sets the rank proportion (or fractional value) that establish the Kth ranked value of the
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partial Hausdorff distance. Experimentally had been shown that 0.6 is a good value to compare shapes.
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.. ocv:function:: void setRankProportion( float rankProportion )
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:param rankProportion: fractional value (between 0 and 1).
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