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ReStructuredText
562 lines
12 KiB
ReStructuredText
Planar Subdivisions
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===================
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.. highlight:: python
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.. index:: CvSubdiv2D
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.. _CvSubdiv2D:
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CvSubdiv2D
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----------
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`id=0.403332162742 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/CvSubdiv2D>`__
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.. class:: CvSubdiv2D
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Planar subdivision.
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.. attribute:: edges
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A :ref:`CvSet` of :ref:`CvSubdiv2DEdge`
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Planar subdivision is the subdivision of a plane into a set of
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non-overlapped regions (facets) that cover the whole plane. The above
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structure describes a subdivision built on a 2d point set, where the points
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are linked together and form a planar graph, which, together with a few
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edges connecting the exterior subdivision points (namely, convex hull points)
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with infinity, subdivides a plane into facets by its edges.
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For every subdivision there exists a dual subdivision in which facets and
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points (subdivision vertices) swap their roles, that is, a facet is
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treated as a vertex (called a virtual point below) of the dual subdivision and
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the original subdivision vertices become facets. On the picture below
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original subdivision is marked with solid lines and dual subdivision
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with dotted lines.
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.. image:: ../pics/subdiv.png
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OpenCV subdivides a plane into triangles using Delaunay's
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algorithm. Subdivision is built iteratively starting from a dummy
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triangle that includes all the subdivision points for sure. In this
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case the dual subdivision is a Voronoi diagram of the input 2d point set. The
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subdivisions can be used for the 3d piece-wise transformation of a plane,
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morphing, fast location of points on the plane, building special graphs
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(such as NNG,RNG) and so forth.
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.. index:: CvSubdiv2DPoint
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.. _CvSubdiv2DPoint:
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CvSubdiv2DPoint
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---------------
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`id=0.753986010152 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/CvSubdiv2DPoint>`__
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.. class:: CvSubdiv2DPoint
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Point of original or dual subdivision.
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.. attribute:: first
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A connected :ref:`CvSubdiv2DEdge`
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.. attribute:: pt
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Position, as a :ref:`CvPoint2D32f`
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.. index:: CalcSubdivVoronoi2D
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.. _CalcSubdivVoronoi2D:
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CalcSubdivVoronoi2D
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-------------------
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`id=0.119097157929 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/CalcSubdivVoronoi2D>`__
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.. function:: CalcSubdivVoronoi2D(subdiv)-> None
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Calculates the coordinates of Voronoi diagram cells.
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:param subdiv: Delaunay subdivision, in which all the points are already added
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:type subdiv: :class:`CvSubdiv2D`
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The function calculates the coordinates
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of virtual points. All virtual points corresponding to some vertex of the
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original subdivision form (when connected together) a boundary of the Voronoi
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cell at that point.
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.. index:: ClearSubdivVoronoi2D
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.. _ClearSubdivVoronoi2D:
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ClearSubdivVoronoi2D
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--------------------
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`id=0.158437620754 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/ClearSubdivVoronoi2D>`__
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.. function:: ClearSubdivVoronoi2D(subdiv)-> None
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Removes all virtual points.
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:param subdiv: Delaunay subdivision
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:type subdiv: :class:`CvSubdiv2D`
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The function removes all of the virtual points. It
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is called internally in
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:ref:`CalcSubdivVoronoi2D`
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if the subdivision
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was modified after previous call to the function.
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.. index:: CreateSubdivDelaunay2D
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.. _CreateSubdivDelaunay2D:
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CreateSubdivDelaunay2D
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----------------------
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`id=0.918020754539 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/CreateSubdivDelaunay2D>`__
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.. function:: CreateSubdivDelaunay2D(rect,storage)-> delaunay_triangulation
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Creates an empty Delaunay triangulation.
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:param rect: Rectangle that includes all of the 2d points that are to be added to the subdivision
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:type rect: :class:`CvRect`
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:param storage: Container for subdivision
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:type storage: :class:`CvMemStorage`
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The function creates an empty Delaunay
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subdivision, where 2d points can be added using the function
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:ref:`SubdivDelaunay2DInsert`
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. All of the points to be added must be within
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the specified rectangle, otherwise a runtime error will be raised.
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Note that the triangulation is a single large triangle that covers the given rectangle. Hence the three vertices of this triangle are outside the rectangle
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``rect``
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.. index:: FindNearestPoint2D
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.. _FindNearestPoint2D:
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FindNearestPoint2D
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------------------
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`id=0.679601866055 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/FindNearestPoint2D>`__
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.. function:: FindNearestPoint2D(subdiv,pt)-> point
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Finds the closest subdivision vertex to the given point.
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:param subdiv: Delaunay or another subdivision
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:type subdiv: :class:`CvSubdiv2D`
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:param pt: Input point
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:type pt: :class:`CvPoint2D32f`
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The function is another function that
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locates the input point within the subdivision. It finds the subdivision vertex that
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is the closest to the input point. It is not necessarily one of vertices
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of the facet containing the input point, though the facet (located using
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:ref:`Subdiv2DLocate`
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) is used as a starting
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point. The function returns a pointer to the found subdivision vertex.
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.. index:: Subdiv2DEdgeDst
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.. _Subdiv2DEdgeDst:
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Subdiv2DEdgeDst
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---------------
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`id=0.723258652692 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/Subdiv2DEdgeDst>`__
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.. function:: Subdiv2DEdgeDst(edge)-> point
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Returns the edge destination.
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:param edge: Subdivision edge (not a quad-edge)
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:type edge: :class:`CvSubdiv2DEdge`
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The function returns the edge destination. The
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returned pointer may be NULL if the edge is from dual subdivision and
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the virtual point coordinates are not calculated yet. The virtual points
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can be calculated using the function
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:ref:`CalcSubdivVoronoi2D`
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.
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.. index:: Subdiv2DGetEdge
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.. _Subdiv2DGetEdge:
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Subdiv2DGetEdge
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---------------
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`id=0.506587189348 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/Subdiv2DGetEdge>`__
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.. function:: Subdiv2DGetEdge(edge,type)-> CvSubdiv2DEdge
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Returns one of the edges related to the given edge.
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:param edge: Subdivision edge (not a quad-edge)
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:type edge: :class:`CvSubdiv2DEdge`
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:param type: Specifies which of the related edges to return, one of the following:
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:type type: :class:`CvNextEdgeType`
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* **CV_NEXT_AROUND_ORG** next around the edge origin ( ``eOnext`` on the picture below if ``e`` is the input edge)
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* **CV_NEXT_AROUND_DST** next around the edge vertex ( ``eDnext`` )
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* **CV_PREV_AROUND_ORG** previous around the edge origin (reversed ``eRnext`` )
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* **CV_PREV_AROUND_DST** previous around the edge destination (reversed ``eLnext`` )
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* **CV_NEXT_AROUND_LEFT** next around the left facet ( ``eLnext`` )
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* **CV_NEXT_AROUND_RIGHT** next around the right facet ( ``eRnext`` )
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* **CV_PREV_AROUND_LEFT** previous around the left facet (reversed ``eOnext`` )
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* **CV_PREV_AROUND_RIGHT** previous around the right facet (reversed ``eDnext`` )
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.. image:: ../pics/quadedge.png
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The function returns one of the edges related to the input edge.
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.. index:: Subdiv2DNextEdge
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.. _Subdiv2DNextEdge:
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Subdiv2DNextEdge
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----------------
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`id=0.406592929731 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/Subdiv2DNextEdge>`__
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.. function:: Subdiv2DNextEdge(edge)-> CvSubdiv2DEdge
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Returns next edge around the edge origin
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:param edge: Subdivision edge (not a quad-edge)
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:type edge: :class:`CvSubdiv2DEdge`
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.. image:: ../pics/quadedge.png
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The function returns the next edge around the edge origin:
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``eOnext``
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on the picture above if
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``e``
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is the input edge)
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.. index:: Subdiv2DLocate
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.. _Subdiv2DLocate:
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Subdiv2DLocate
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--------------
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`id=0.614412184993 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/Subdiv2DLocate>`__
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.. function:: Subdiv2DLocate(subdiv, pt) -> (loc, where)
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Returns the location of a point within a Delaunay triangulation.
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:param subdiv: Delaunay or another subdivision
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:type subdiv: :class:`CvSubdiv2D`
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:param pt: The point to locate
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:type pt: :class:`CvPoint2D32f`
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:param loc: The location of the point within the triangulation
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:type loc: int
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:param where: The edge or vertex. See below.
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:type where: :class:`CvSubdiv2DEdge`, :class:`CvSubdiv2DPoint`
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The function locates the input point within the subdivision. There are 5 cases:
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*
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The point falls into some facet.
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``loc``
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is
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``CV_PTLOC_INSIDE``
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and
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``where``
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is one of edges of the facet.
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*
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The point falls onto the edge.
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``loc``
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is
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``CV_PTLOC_ON_EDGE``
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and
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``where``
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is the edge.
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*
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The point coincides with one of the subdivision vertices.
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``loc``
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is
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``CV_PTLOC_VERTEX``
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and
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``where``
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is the vertex.
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*
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The point is outside the subdivsion reference rectangle.
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``loc``
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is
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``CV_PTLOC_OUTSIDE_RECT``
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and
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``where``
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is None.
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*
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One of input arguments is invalid. The function raises an exception.
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.. index:: Subdiv2DRotateEdge
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.. _Subdiv2DRotateEdge:
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Subdiv2DRotateEdge
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------------------
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`id=0.775095566923 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/Subdiv2DRotateEdge>`__
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.. function:: Subdiv2DRotateEdge(edge,rotate)-> CvSubdiv2DEdge
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Returns another edge of the same quad-edge.
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:param edge: Subdivision edge (not a quad-edge)
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:type edge: :class:`CvSubdiv2DEdge`
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:param rotate: Specifies which of the edges of the same quad-edge as the input one to return, one of the following:
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* **0** the input edge ( ``e`` on the picture below if ``e`` is the input edge)
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* **1** the rotated edge ( ``eRot`` )
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* **2** the reversed edge (reversed ``e`` (in green))
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* **3** the reversed rotated edge (reversed ``eRot`` (in green))
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:type rotate: int
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.. image:: ../pics/quadedge.png
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The function returns one of the edges of the same quad-edge as the input edge.
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.. index:: SubdivDelaunay2DInsert
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.. _SubdivDelaunay2DInsert:
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SubdivDelaunay2DInsert
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----------------------
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`id=0.291010420302 Comments from the Wiki <http://opencv.willowgarage.com/wiki/documentation/py/imgproc/SubdivDelaunay2DInsert>`__
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.. function:: SubdivDelaunay2DInsert(subdiv,pt)-> point
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Inserts a single point into a Delaunay triangulation.
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:param subdiv: Delaunay subdivision created by the function :ref:`CreateSubdivDelaunay2D`
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:type subdiv: :class:`CvSubdiv2D`
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:param pt: Inserted point
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:type pt: :class:`CvPoint2D32f`
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The function inserts a single point into a subdivision and modifies the subdivision topology appropriately. If a point with the same coordinates exists already, no new point is added. The function returns a pointer to the allocated point. No virtual point coordinates are calculated at this stage.
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