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561 lines
10 KiB
561 lines
10 KiB
Planar Subdivisions |
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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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.. 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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.. 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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.. 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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.. 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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.. 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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. |
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.. index:: FindNearestPoint2D |
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.. _FindNearestPoint2D: |
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FindNearestPoint2D |
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------------------ |
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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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.. 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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.. 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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.. 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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.. 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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``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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``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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``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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.. 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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.. 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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