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Posted 3 Jan 2002

A C++ implementation of Douglas-Peucker Line Approximation Algorithm

, 3 Mar 2003
DP Line approximation algorithm is a well-known method to approximate 2D lines. It is quite fast, O(nlog_2(n)) for a n-points line and can drastically compress a data curve. Here, a fully OOP implementation is given.
// DPHullGL.h: interface for the CDPHullGL class.

#if !defined(AFX_DPHULLGL_H__CC98539B_1112_42CF_9E10_C31D46DA9771__INCLUDED_)
#define AFX_DPHULLGL_H__CC98539B_1112_42CF_9E10_C31D46DA9771__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include "KeyFramer.h"
#include "DPHull.h"

using namespace hull;

class CDPHullGL
	typedef std::vector< hull::TPoint< float > > PointContainer;
	typedef std::list< PointContainer::const_iterator > KeyContainer;
	typedef hull::TDPHull<float, PointContainer, KeyContainer> Hull;

	virtual ~CDPHullGL();
	void SetTol( double dTol);
	double GetTol() const				{	return m_dpHull.GetTol();};
	UINT GetPointSize() const			{	return m_dpHull.GetPointSize();};
	UINT GetKeySize() const				{	return m_dpHull.GetKeySize();};
	Hull& GetHull() {	return m_dpHull;};

	void SetPoint( UINT i, double x, double y);
	void ResizePoints(UINT nPoints);

	void ComputeBoundingBox();
	void Simplify();
	UINT ShrinkNorm(double dScale, double dScaleTol=0.05, double eTolRight=0.1,UINT nMaxIter=100);

	void PlotPoints();
	void PlotKeys(CWGL& wgl);

	Hull m_dpHull;
	static void PlotKeyMethod( const TLineApproximator<float,PointContainer, KeyContainer>& la);

	UINT m_iterHull;

	bool m_bHull;


#endif // !defined(AFX_DPHULLGL_H__CC98539B_1112_42CF_9E10_C31D46DA9771__INCLUDED_)

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About the Author

Jonathan de Halleux
United States United States
Jonathan de Halleux is Civil Engineer in Applied Mathematics. He finished his PhD in 2004 in the rainy country of Belgium. After 2 years in the Common Language Runtime (i.e. .net), he is now working at Microsoft Research on Pex (

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