QwtWeedingCurveFitter(3)       Qwt User's Guide       QwtWeedingCurveFitter(3)

NAME
       QwtWeedingCurveFitter - A curve fitter implementing Douglas and Peucker
       algorithm.


SYNOPSIS
       #include <qwt_weeding_curve_fitter.h>

       Inherits QwtCurveFitter.

   Public Member Functions
       QwtWeedingCurveFitter (double tolerance=1.0)
       virtual ~QwtWeedingCurveFitter ()
           Destructor.
       void setTolerance (double)
       double tolerance () const
       void setChunkSize (uint)
       uint chunkSize () const
       virtual QPolygonF fitCurve (const QPolygonF &) const override
       virtual QPainterPath fitCurvePath (const QPolygonF &) const override

   Additional Inherited Members

Detailed Description
       A curve fitter implementing Douglas and Peucker algorithm.

       The purpose of the Douglas and Peucker algorithm is that given a
       'curve' composed of line segments to find a curve not too dissimilar
       but that has fewer points. The algorithm defines 'too dissimilar' based
       on the maximum distance (tolerance) between the original curve and the
       smoothed curve.

       The runtime of the algorithm increases non linear ( worst case O( n*n )
       ) and might be very slow for huge polygons. To avoid performance issues
       it might be useful to split the polygon ( setChunkSize() ) and to run
       the algorithm for these smaller parts. The disadvantage of having no
       interpolation at the borders is for most use cases irrelevant.

       The smoothed curve consists of a subset of the points that defined the
       original curve.

       In opposite to QwtSplineCurveFitter the Douglas and Peucker algorithm
       reduces the number of points. By adjusting the tolerance parameter
       according to the axis scales QwtSplineCurveFitter can be used to
       implement different level of details to speed up painting of curves of
       many points.

       Definition at line 38 of file qwt_weeding_curve_fitter.h.

Constructor & Destructor Documentation
   QwtWeedingCurveFitter::QwtWeedingCurveFitter (double tolerance = 1.0)
       [explicit]
       Constructor

       Parameters
           tolerance Tolerance

       See also
           setTolerance(), tolerance()

       Definition at line 50 of file qwt_weeding_curve_fitter.cpp.

Member Function Documentation
   uint QwtWeedingCurveFitter::chunkSize () const
       Returns
           Maximum for the number of points passed to a run of the algorithm -
           or 0, when unlimited

       See also
           setChunkSize()

       Definition at line 114 of file qwt_weeding_curve_fitter.cpp.

   QPolygonF QwtWeedingCurveFitter::fitCurve (const QPolygonF & points) const
       [override],  [virtual]
       Parameters
           points Series of data points

       Returns
           Curve points

       See also
           fitCurvePath()

       Implements QwtCurveFitter.

       Definition at line 124 of file qwt_weeding_curve_fitter.cpp.

   QPainterPath QwtWeedingCurveFitter::fitCurvePath (const QPolygonF & points)
       const [override],  [virtual]
       Parameters
           points Series of data points

       Returns
           Curve path

       See also
           fitCurve()

       Implements QwtCurveFitter.

       Definition at line 151 of file qwt_weeding_curve_fitter.cpp.

   void QwtWeedingCurveFitter::setChunkSize (uint numPoints)
       Limit the number of points passed to a run of the algorithm

       The runtime of the Douglas Peucker algorithm increases non linear with
       the number of points. For a chunk size > 0 the polygon is split into
       pieces passed to the algorithm one by one.

       Parameters
           numPoints Maximum for the number of points passed to the algorithm

       See also
           chunkSize()

       Definition at line 101 of file qwt_weeding_curve_fitter.cpp.

   void QwtWeedingCurveFitter::setTolerance (double tolerance)
       Assign the tolerance

       The tolerance is the maximum distance, that is acceptable between the
       original curve and the smoothed curve.

       Increasing the tolerance will reduce the number of the resulting
       points.

       Parameters
           tolerance Tolerance

       See also
           tolerance()

       Definition at line 76 of file qwt_weeding_curve_fitter.cpp.

   double QwtWeedingCurveFitter::tolerance () const
       Returns
           Tolerance

       See also
           setTolerance()

       Definition at line 85 of file qwt_weeding_curve_fitter.cpp.


Author
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Version 6.2.0                   Sun Jul 18 2021       QwtWeedingCurveFitter(3)