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src/qwt_weeding_curve_fitter.h

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+/******************************************************************************
+ * Qwt Widget Library
+ * Copyright (C) 1997   Josef Wilgen
+ * Copyright (C) 2002   Uwe Rathmann
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the Qwt License, Version 1.0
+ *****************************************************************************/
+
+#ifndef QWT_WEEDING_CURVE_FITTER_H
+#define QWT_WEEDING_CURVE_FITTER_H
+
+#include "qwt_curve_fitter.h"
+
+/*!
+   \brief 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.
+ */
+class QWT_EXPORT QwtWeedingCurveFitter : public QwtCurveFitter
+{
+  public:
+    explicit QwtWeedingCurveFitter( double tolerance = 1.0 );
+    virtual ~QwtWeedingCurveFitter();
+
+    void setTolerance( double );
+    double tolerance() const;
+
+    void setChunkSize( uint );
+    uint chunkSize() const;
+
+    virtual QPolygonF fitCurve( const QPolygonF& ) const QWT_OVERRIDE;
+    virtual QPainterPath fitCurvePath( const QPolygonF& ) const QWT_OVERRIDE;
+
+  private:
+    virtual QPolygonF simplify( const QPolygonF& ) const;
+
+    class Line;
+
+    class PrivateData;
+    PrivateData* m_data;
+};
+
+#endif