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# 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.

## Introduction

When working with mathematical simulations or engineering problems, it is not unusual to handle curves that contains thousands of points. Usually, displaying all the points is not useful, a number of them will be rendered on the same pixel since the screen precision is finite. Hence, you use a lot of resource for nothing!

This article presents a fast 2D-line approximation algorithm based on the Douglas-Peucker algorithm (see [1]), well-known in the cartography community. It computes a hull, scaled by a tolerance factor, around the curve by choosing a minimum of key points. This algorithm has several advantages:

• It is fast!: For a n point curve, computation time of the approximation is proportional to nlog_2(n),
• You don't need a priori knowledge on the curve,
• The compression ratio can be easily tuned using the tolerance parameter.

The class has been integrated to a plotting library: Plot Graphic Library.

## Douglas-Peucker (DP) Line Simplification Algorithm

The DP line simplification algorithm was originally proposed in [1]. John Hershberger and Jack Snoeyink have implemented it in C in [2] as a package named DPSimp:

DPsimp is a Douglas-Peucker line simplification algorithm implementation by John Hershberger and Jack Snoeyink. They analyze the line simplification algorithm reported by Douglas and Peucker and show that its worst case is quadratic in n, the number of input points. The algorithm is based on path hulls, that uses the geometric structure of the problem to attain a worst-case running time proportional to nlog_2(n), which is the best case of the Douglas algorithm.

The algorithm is based on a recursive construction of path hull, as depicted in the picture below. They did all the hard work (writing the base code in C), I ported it to C++ templates.

## Modifications to DPSimp

DPSimp was using a recursive call in the DP method. This could lead to a stack overflow when the algorithm would go deep in recursion. To avoid this problem an internal stack has been added to the class to mimic the recursive function call without stack overflow.

## Concepts and class design

Let the points denote all the points of the original curve and the keys the points from the original curve that are kept for the approximation.

The idea is that the user provides a container for the points, denoted PointContainer, and for the keys, denoted KeyContainer, and the link between those containers will be the line simplification class, denoted LineApproximator.

How do we build a class hierarchy without restricting ourselves to particular container? In fact, one user might store it's points in vector< pair<T,T>> and another one in 2 separate vector<T>. Of course, the same argument applies to the KeyContainer.

A possible answer is templating. Passing the PointContainer and KeyContainer as template arguments for LineApproximator allows to build the approximation class without specifying the containers, since the class is built at compilation time (We could write interface for those containers but in fact, I'm too lazy for that :) ).

With this idea in mind, here are the specifications of the container:

### PointContainer

Let

• Point a structure, template or class that has x,y of type T as member,
• PointRef a structure, template or class that has x,y of type T& as member,

PointContainer behaves like a vector of Point:

• has clear(), size() and resize() methods,
• has random access iterator,
• const_iterator points to a structure similar to Point,
• iterator points to a structure similar to PointRef
• operator[] const returns a Point,
• operator[] returns a PointRef

A simple example of valid PointContainer is

vector<Point>

However, a hybrid container has been developed to handle the case where x and y are in separate containers (See below).

### KeyContainer

KeyContainer behaves like a list of PointContainer::const_iterator:

• has size(), clear() methods,
• support push_back method

A simple example of valid KeyContainer is

vector<PointContainer::const_iterator>

Again, a hydrid container to handle the case where the keys must be outputted in separate containers is provided.

## Templates

All the classes are templated to support float and double version of the algorithm.

The template TDPHull is the user interface to the DP algorithm. However, it relies on a series of subclasses detailed below:

NameDescriptionUse
TLine<T, TPointContainer, TKeyContainer>2D Line templatePoints and keys
TLineApproximator<T, TPointContainer, TKeyContainer>2D Line approximator base classDefault interface to approximation algorithms
TDPHull<T, TPointContainer, TKeyContainer>Implementing Douglas-Peukler algorithmUser front end
TPathHull<T, TPointContainer, TKeyContainer>Path hullInternal in TDPHull<T>
TPoint<T>A pair of T: x, yTemplate for 2D point TLineApproximator<T>
TPointRef<T>A pair of T&: x, yTemplate for 2D point TLineApproximator<T>
SHomog2D Homogenous point, T x,y,wInternal structure to TLineApproximator<T>

## How to use TDPHull?

In the following examples, we adopt the following notations

using namespace hull; // all classes are in the hull namespace,
using namespace std; // using some STL containers

// defining the point container
typedef vector<TPoint<float>> VectorPointContainer;
// defining the key container
typedef vector<MyPointContainer::const_iterator> ListKeyContainer;
// defining the line approximation class
typedef TDPHull<float, VectorPointContainer, ListKeyContainer> CDPHullF;
CDPHullF dp; // a DPHull object, note that you can also work with doubles

The approximation methods throw exception, so you should always enclose them in a try-catch statement.

### Normalization

The data points are, by default, normalized before approximation. This is in order to reduce numerical errors in the gradients computations. This happens when the data is badly scaled: using big numbers close together will lead to disastrous loss of significant numbers.

However, if you feel confident about your data, you can disable it by using SetNormalization.

### Handling points and keys

Get a reference to the point container and modify it:

// getting reference to container,
TDPHull<float>::PointContainer& pc = dp.GetPoints();
for (UINT i=0;i<pc.size();i++)
{
pc[i].x=...;
pc[i].y=...;
}

If you are using normalization (default behavior), do not forget to re-compute the data bounding box after your changes:

dp.ComputeBoundingBox();

### Approximation tuning

You can control the compression ratio by different ways:

• Setting the tolerance
// Setting tolerance of approximation
dp.SetTol(0.5);
• Setting a compression ratio, an acceptable compression threshold:
// dp will find the tolerance corresponding to 10 % of
// the original points, with 5% of possible error.
try
{
dp.ShrinkNorm(0.1,0.05);
}
catch(TCHAR* str)
{
// catch and process errors throw by dp
// example: output to cerr
cerr<<str<<endl;
}

The method uses dichotomy to accelerate convergence.

• Setting the desired number of points, an acceptable number of points threshold:
// dp will find the tolerance corresponding to 100
// in the approximated curve, with 5 points of possible error.
try
{
dp.Shrink(100,5);
}
catch(TCHAR* str)
{
// catch and process errors throw by dp
...
}

### Simplifaction

The easiest part of the job:

try
{
dp.Simplify();
}
catch(TCHAR* str)
{
// catch and process errors throw by dp
...
}

or by using ShrinkNorm, Shrink methods.

### Accessing the approximated curve

The keys are stored as PointContainer::const_iterator. You can access the key container by using GetKeys:

// getting conts reference to keys
const TDPHull<float>::KeyContainer& kc = dp.GetKeys();
TDPHull<float>::KeyContainer::const_iterator it; // iterator for keys
for (it = kc.begin(); it != kc.end(); it++)
{
// it is an const_iterator pointing to a PointContainer::const_iterator
xi=(*it)->x;
yi=(*it)->y;
}

All you have to do is inherit a class from TLineApproximator and override the function ComputeKeys.

## Hydrid containers

You can implement your own containers for points and keys as long as they meet the requirements.

### Separate containers for x,y

It is not unusual to have x,y stored in separate containers and moreover these containers are not of the same type. To tackle this problem, two wrapper templates have been written: TPointDoubleContainer and TKeyDoubleContainer which serve as an interface between the approximation algorithms and the containers:

CVectorX vX;    // the vector of x coordinates
CVectorY vY;    // the vector of y coordinates

// defining the hydrid container
typedef TPointDoubleContainer<float, CVectorX,
CVectorY> HybridPointContainer;

// a list of key x coordinates
CListX lKeyX;
// a vector of key y coordinates, any container
// that has push_back will do the job :)
CVectorY vKeyY;
// defining the hydrid container
typedef TKeyDoubleContainer<float, CListX, CVectorY> HybridKeyContainer;

// creating approximator
TDPHull< float, HybridPointContainer, HydridKeyContainer> dp;
// attaching point containers
dp.GetPoints().SetContainers( &vX, &vY);
// attaching key containers
dp.GetKeys().SetContainers( &lKeyX, &vKeyY);
// dp is now ready to work

## Using the demo

The demo shows a real time approximation of a curve by different algorithms.

• You can stop/start the animation using the toolbar buttons,
• You can modify the shrinking ration with the scroll bar,
• You can load your own data with the menu, File->Load Data Set. The file must be formatted with a pair x,y per line.

## Using it in your project

Insert the following files in your project and you're done.

LineApproximator.h,DPHull.h, PathHull.h

## Known issues

• The original curve must not self-intersect. This means also that the start and end points must be different, no closed curve !
• Sick dataset and stack overflow: solved. The problem was due to recursion leading to stack overflow. It is solved now.

## Update history

• 04-03-2003
• Got rid of DP recursion by adding an internal function call stack. Hence, the stack overflow problem is solved!!!
• Applied stuff I learned in Effective STL to the classes: using algorithms, functors, etc...
• Changed <CODE lang=c++>class T to <CODE lang=c++>typename T
• Better floating point comparison using boost::close_at_tolerance
• 15-11-2002
• More and more templating,
• Detecting when curve is closed
• Hybrid containers
• Fixed bug in compute limits
• Added LOTS of ASSERT, so Debug version is significantly slower than release build
• 7-11-2002
• Fixed a bug in the SLimits structure (GetCenterY)
• TPathHull working with iterators rather that SPoint*
• Added exception to handle errors
• Fixed a bug in TDPHull::ComputeKeys. Was using pc.end() rather that pc.end()--
• 6-11-2002
• Added base class TLineApproximator
• Added proposed algorithm by S.Rog: see TKeyFramer, TGlobalKeyFramer, TDispKeyFramer, TVectKeyFramer
• Updated demo
• 3-11-2002
• Added data normalization for better numerical behavior. Avoids the algorithm to crash when using badly conditioned data. Problem submitted by Corey W.
• Templated version
• Got rid of macro and rewrote in more OOP style

## References

1. D. H. Douglas and T. K. Peucker. Algorithms for the reduction of the number of points required to represent a line or its caricature. The Canadian Cartographer, 10(2):112--122, 1973.
2. J. Hershberger and J. Snoeyink. Speeding up the Douglas-Peucker line simplification algorithm. In Proc. 5th Intl. Symp. Spatial Data Handling. IGU Commission on GIS, pages 134--143, 1992. (home page).

A list of licenses authors might use can be found here

## Share

 Engineer 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 (http://research.microsoft.com/pex).

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 I have ported it to Visual Studio 2003 but without much testing. The updated version of the four include files (DPHull.h, LineApproximator.h, PathHull.h and Containers.h) can be found below. Most of the job was limited to the insertion of "typename" keywords at required places. LineApproximator.h ------------------ /* Plot Graphic Library Copyright (C) 2002 Pelikhan, Inc. All rights reserved Go to http://eauminerale.syldavie.csam.ucl.ac.be/peli/pgl/pgl.html for the latest PGL binaries This software is NOT freeware. This software is provided "as is", with no warranty. Read the license agreement provided with the files This software, and all accompanying files, data and materials, are distributed "AS IS" and with no warranties of any kind, whether express or implied. his disclaimer of warranty constitutes an essential part of the agreement. In no event shall Pelikhan, or its principals, shareholders, officers, employees, affiliates, contractors, subsidiaries, or parent organizations, be liable for any incidental, consequential, or punitive damages whatsoever relating to the use of PGL, or your relationship with Pelikhan. Author: Jonathan de Halleux, dehalleux@auto.ucl.ac.be */ #if !defined(AFX_LINEAPPROXIMATOR_H__F5E6E8DC_1185_4AC0_A061_7B3309700E9D__INCLUDED_) #define AFX_LINEAPPROXIMATOR_H__F5E6E8DC_1185_4AC0_A061_7B3309700E9D__INCLUDED_ #if _MSC_VER > 1000 #pragma once #endif // _MSC_VER > 1000 #include #ifndef ASSERT #ifdef _DEBUG #define ASSERT(a) _ASSERT(a); #else #define ASSERT(a) #endif #endif #ifdef min #undef min #endif #ifdef max #undef max #endif #include #include #include #include #include /*! \defgroup LAGroup Line approximation algorithms */ namespace hull { /*! \brief A point (x,y) \param T float or double A pair of (x,y) values. \ingroup LAGroup */ template class TPoint { public: //! Default constructor TPoint( T _x = 0, T _y=0):x(_x), y(_y){}; //! Assignement constructor TPoint& operator = ( const TPoint& t) { if (&t != this){ x=t.x; y=t.y;} return *this;}; //! x value T x; //! y value T y; }; /*! \brief A point (x,y) with references \param T float or double \ingroup LAGroup */ template class TPointRef { public: //! Default contructor TPointRef():x(xDummy),y(yDummy){}; /*! \brief Constructor with 2 values \param _x value to get reference to. \param _y value to get reference to. */ TPointRef(T& _x, T& _y):x(_x),y(_y){}; //! Assignement constructor TPointRef& operator = (const TPointRef& t) { if (this != &t){ x=t.x;y=t.y;} return *this;}; //! Assignement constructor with point TPointRef& operator = (TPoint t) { x=t.x;y=t.y; return *this;}; //! x, reference to a value T& x; //! y, reference to a value T& y; private: static T xDummy; static T yDummy; }; template T TPointRef::xDummy=0; template T TPointRef::yDummy=0; /*! \brief Virtual base class for Line approximator classes \par Template arguments \param T float or double \param TPointContainer a container of points (structure with x,y) with random access iterators \param TKeyContainer a container of TPointContainer::const_iterator (structure with x,y) with single direction iterators \par Notations: - points : data to interpolate - keys : selected points from available set that interpolate within the desired tolerance \par Containers: - Points are stored in a #PointContainer. #PointContainer is a container such that #- has random access iterator, #- value_type is a structure/class with x,y members - Keys are stored in a #KeyContainer. #KeyContainer is a container such that: #- has single directional iterator, #- value_type is PointContainer::const_iterator \par Data normalization: To avoid numerical instability when computing cross product and so, data is normalized ( see #NormalizePoints ). To enable/disable normalization, use #SetNormalization. \ingroup LAGroup */ template class TLine { public: //! \name Structures and typedefs //@{ //! Point container typedef TPointContainer PointContainer; //! Key container typedef TKeyContainer KeyContainer; //! 2D homogenous point struct SHomog { public: //! Default constructor SHomog(T _x=0, T _y=0, T _w=1) { x=_x; y=_y; w=_w;}; T x; T y; T w; }; /*! \brief returns square of euclidian distance */ static T SqrDist( typename const TPointContainer::const_iterator& p, typename const TPointContainer::const_iterator& q) { T dx=p->x-q->x; T dy=p->y-q->y; return dx*dx+dy*dy; } /*! \brief Cross product \param p an iterator with x,y members \param q an iterator with x,y members \result r cross product of p,q The euclidian cross product of p,q: \f[ \vec r = \vec p \times \vec q = \left( \begin{array}{c} p_x q_y - p_y q_x \\ -q_y + p_y \\ q_x - p_x \end{array}\right)\f] */ static void CrossProduct( typename const TPointContainer::const_iterator& p, typename const TPointContainer::const_iterator& q, SHomog& r) { r.w = p->x * q->y - p->y * q->x; r.x = - q->y + p->y; r.y = q->x - p->x; }; /*! \brief Dot product \param p an iterator with x,y members \param q an 2D homogenous point \result dot product of p,q The euclidian dot product of p,q: \f[ <\vec p, \vec q> = q_w + p_x q_x + p_y q_y \f] */ static T DotProduct( typename const TPointContainer::const_iterator& p, const SHomog& q) { return q.w + p->x*q.x + p->y*q.y; }; /*! \brief Dot product \param p an iterator with x,y members \param q an iterator with x,y members \result dot product of p,q The euclidian dot product of p,q: \f[ < \vec p,\vec q> = p_x q_x + p_y q_y \f] */ static T DotProduct( typename const TPointContainer::const_iterator& p, typename const TPointContainer::const_iterator& q) { return p->x*q->x + p->y*q->y; }; /*! \brief Linear combination of points \param a p multiplier \param p a point \param b q multiplier \param q a point \param r linear combination of p,q The linear combination is: \f[ \vec r = a \vec p + b \vec q \f] */ static void LinComb( T a, typename const TPointContainer::const_iterator& p, T b, typename const TPointContainer::const_iterator& q, typename const TPointContainer::const_iterator& r) { r->x = a * p->x + b * q->x; r->y = a * p->y + b * q->y; }; //! Internal limit structure struct SLimits { T dMinX; T dMaxX; T dMinY; T dMaxY; T GetCenterX() { return static_cast((dMaxX+dMinX)/2.0);}; T GetCenterY() { return static_cast((dMaxY+dMinY)/2.0);}; T GetWidth() { return static_cast(dMaxX-dMinX);}; T GetHeight() { return static_cast(dMaxY-dMinY);}; }; //! T container typedef std::vector TVector; //@} //! Default constructor TLine():m_bNormalization(true){}; //! \name Point handling //@{ //! returns number of points size_t GetPointSize() const { return m_cPoints.size();}; //! return vector of points PointContainer& GetPoints() { return m_cPoints;}; //! return vector of points, const const PointContainer& GetPoints() const { return m_cPoints;}; //@} //! \name Key handling //@{ //! returns number of keys size_t GetKeySize() const { return m_cKeys.size();}; //! return keys KeyContainer& GetKeys() { return m_cKeys;}; //! return keys, const const KeyContainer& GetKeys() const { return m_cKeys;}; //@} //! \name Helpers //@{ //! Setting points from vectors void SetPoints( const std::vector& vX, const std::vector& vY); //! Returning keys to vectors void GetKeys( std::vector& vX, std::vector& vY) const; //@} //! \name Bounding box //@{ //! compute the bounding box void ComputeBoundingBox(); //! return the point bounding box const SLimits& GetBoundingBox() const { return m_limits;}; //@} //! \name Normalization //@{ /*! \brief Point normalization Let \f$(x_i,y_i)\f$, the original points and \f$(\hat x_x, \hat y_i)\f$ the normalized points: \f[ \hat x_i = \frac{x_i - \bar x]}{\max_i (x_i-x_j)} \f] where \f$\bar x\f$, \f$\bar y\f$ denote respectively the mean value of the \f$x_i\f$ and \f$y_i\f$. \sa DeNormalizePoints */ void NormalizePoints(); /*! \brief Roll back normalization \sa NormalizePoints */ void DeNormalizePoints(); //! enabled, disable normalization void SetNormalization( bool bEnabled = true) { m_bNormalization = true;}; //! returns true if normalizing bool IsNormalization() const { return m_bNormalization;}; //@} //! \name Double points checking and loop... //@{ /*! \brief Discard double points For each pair of points \f$p_i, p_{i+1}\f$, discards \f$p_{i+1}\f$ if \f[ \| p_i - p_{i+1} \| < \varepsilon \f] */ void DiscardDoublePoints(); //! Test for loops void FindLoop(size_t uStartPoint, size_t& uEndPoint); //@} protected: //! \name Attributes //@{ TPointContainer m_cPoints; TKeyContainer m_cKeys; SLimits m_limits; bool m_bNormalization; //@} }; namespace priv { template struct PredX : public std::binary_function< typename Container::iterator, typename Container::iterator, bool> { bool operator()( typename const Container::value_type& p1, typename const Container::value_type& p2) { return m_pred(p1.x, p2.x); }; protected: Pred m_pred; }; template struct PredY : public std::binary_function< typename Container::iterator, typename Container::iterator, bool> { bool operator()( typename const Container::value_type& p1, typename const Container::value_type& p2) { return m_pred(p1.y, p2.y); }; protected: Pred m_pred; }; }; template void TLine::ComputeBoundingBox() { if (m_cPoints.size() < 2) return; PointContainer::const_iterator it = (*((const TPointContainer*)&m_cPoints)).begin(); //finding minimum and maximum... m_limits.dMinX=std::min_element( m_cPoints.begin(), m_cPoints.end(), priv::PredX >() )->x ; m_limits.dMaxX=std::max_element( m_cPoints.begin(), m_cPoints.end(), priv::PredX >() )->x ; m_limits.dMinY=std::min_element( m_cPoints.begin(), m_cPoints.end(), priv::PredY >() )->y ; m_limits.dMaxY=std::max_element( m_cPoints.begin(), m_cPoints.end(), priv::PredY >() )->y ; if ( fabs( m_limits.GetWidth() ) < std::numeric_limits::epsilon() ) { m_limits.dMaxX = m_limits.dMinX+1; } if ( fabs( m_limits.GetHeight() ) < std::numeric_limits::epsilon() ) { m_limits.dMaxY = m_limits.dMinY+1; } } namespace priv { template struct Rect { Rect( T xm, T ym, T dx, T dy) :m_xm(xm),m_ym(ym),m_dx(dx),m_dy(dy){}; protected: T m_xm; T m_ym; T m_dx; T m_dy; }; template struct NormalizePoint : public std::unary_function< TPoint& , int>, public Rect { NormalizePoint( T xm, T ym, T dx, T dy) : Rect(xm,ym,dx,dy){}; int operator() ( TPoint& point) { point.x=(point.x-m_xm)/m_dx; point.y=(point.y-m_ym)/m_dy; return 0; }; }; template struct DeNormalizePoint : public std::unary_function< TPoint& , int>, public Rect { DeNormalizePoint( T xm, T ym, T dx, T dy) : Rect(xm,ym,dx,dy){}; int operator() ( TPoint& point) { point.x=m_xm+point.x*m_dx; point.y=m_ym+point.y*m_dy; return 0; }; }; }; template void TLine::NormalizePoints() { T xm,ym,dx,dy; // normalizing... xm=m_limits.GetCenterX(); ym=m_limits.GetCenterY(); dx=m_limits.GetWidth(); dy=m_limits.GetHeight(); std::for_each( m_cPoints.begin(), m_cPoints.end(), priv::NormalizePoint( xm, ym, dx, dy) ); } template void TLine::DeNormalizePoints() { T xm,ym,dx,dy; // normalizing... xm=m_limits.GetCenterX(); ym=m_limits.GetCenterY(); dx=m_limits.GetWidth(); dy=m_limits.GetHeight(); std::for_each( m_cPoints.begin(), m_cPoints.end(), priv::DeNormalizePoint( xm, ym, dx, dy) ); } template void TLine::DiscardDoublePoints() { // creating a list... TPointContainer& pc=GetPoints(); TPointContainer::iterator it, it1; T epsilon2=std::numeric_limits::epsilon(); #ifdef _DEBUG size_t count=0; #endif it1=it=pc.begin(); ++it1; while (it !=pc.end() && it1!=pc.end()) { if ( SqrDist(it, it1) < epsilon2 ) { it1=pc.erase(it1); } else { ++it; ++it1; } } #ifdef _DEBUG TRACE( _T("Numer of (double) points erased: %d\n"), count); #endif }; template void TLine::SetPoints( const std::vector& vX, const std::vector& vY) { TPointContainer& pc=GetPoints(); const size_t n = __min( vX.size(), vY.size()); pc.resize(n); for (size_t i=0;i( vX[i], vY[i]); } }; template void TLine::GetKeys( std::vector& vX, std::vector& vY) const { const TKeyContainer& kc=GetKeys(); TKeyContainer::const_iterator it; size_t i; vX.resize(kc.size()); vY.resize(kc.size()); for (it=kc.begin(), i=0;it!=kc.end();it++, i++) { vX[i]=(*it)->x; vY[i]=(*it)->y; } }; template void TLine::FindLoop(size_t uStartPoint, size_t& uEndPoint) { }; /*! \brief Base class for line approximators \ingroup LAGroup */ template class TLineApproximator : virtual public TLine { public: //! \name Constructor //@{ TLineApproximator(): m_dTol(0) {m_limits.dMinX=m_limits.dMinY=0;m_limits.dMaxX=m_limits.dMaxY=1;}; ~TLineApproximator(){}; //@} //! \name Tolerance //@{ //! sets the tolerance void SetTol( double dTol) { m_dTol = __max( dTol, 0);}; //! return current tolerance double GetTol() const { return m_dTol;}; //@} //! \name Simplification functions //@{ //! Initialize simplification void ClearKeys() { m_cKeys.clear();}; //! Compute the keys void Simplify(); /*! Shrink to compression level \param dScale scaling to apply [0...1] \param dScaleTol [optional] tolerance with respect to dScale, default is 0.05 \param eTolRight [optional] first estimate on right tolerance \param nMaxIter [optional] maximum number of iterations, default is 250 \return number of estimations */ size_t ShrinkNorm( T dScale, T dScaleTol = 0.05, T eTolRight = -1, size_t nMaxIter = 250); /*! Shrink to a specified number of points \param n desired number of points in the approximate curve \param nTol [optional] tolerance with respect to n, default is 10 \param eTolRight [optional] first estimate on right tolerance \param nMaxIter [optional] maximum number of iterations, default is 250 \return number of estimations */ size_t Shrink( size_t nDesiredPoints, size_t nTol = 10, T eTolRight = -1, size_t nMaxIter = 250); //@} protected: //! \name Virtual functions //@{ /*! \brief Virtual approximation function This function must be overriden in inherited classes. To implement your own algorithm, override this function. */ virtual void ComputeKeys() { ClearKeys();}; //@} private: T m_dTol; }; template size_t TLineApproximator::ShrinkNorm( T dScale, T dScaleTol, T eTolRight ,size_t nMaxIter) { // number of points wanted... size_t uWantedPoints= __min(m_cPoints.size(), __max(2, static_cast(floor(m_cPoints.size()*dScale)))); size_t uTol = __min(m_cPoints.size(), __max(0, static_cast(floor(m_cPoints.size()*dScaleTol)) )); return Shrink( uWantedPoints, uTol, eTolRight, nMaxIter); } namespace priv { // (C) Copyright Gennadiy Rozental 2001-2002. // Permission to copy, use, modify, sell and distribute this software // is granted provided this copyright notice appears in all copies. // This software is provided "as is" without express or implied warranty, // and with no claim as to its suitability for any purpose. // See http://www.boost.org for most recent version including documentation. // // File : $RCSfile: floating_point_comparison.hpp,v$ // // Version : $Id: floating_point_comparison.hpp,v 1.6 2002/09/16 08:47:29 rogeeff Exp$ // // Description : defines algoirthms for comparing 2 floating point values // *************************************************************************** template inline FPT fpt_abs( FPT arg ) { return arg < 0 ? -arg : arg; } // both f1 and f2 are unsigned here template inline FPT safe_fpt_division( FPT uf1, FPT uf2 ) { return ( uf1 < 1 && uf1 > uf2 * std::numeric_limits::max()) ? std::numeric_limits::max() : ((uf2 > 1 && uf1 < uf2 * std::numeric_limits::min() || uf1 == 0) ? 0 : uf1/uf2 ); } template class close_at_tolerance { public: explicit close_at_tolerance( FPT tolerance, bool strong_or_weak = true ) : p_tolerance( tolerance ),m_strong_or_weak( strong_or_weak ) { }; explicit close_at_tolerance( int number_of_rounding_errors, bool strong_or_weak = true ) : p_tolerance( std::numeric_limits::epsilon() * number_of_rounding_errors/2 ), m_strong_or_weak( strong_or_weak ) {} bool operator()( FPT left, FPT right ) const { FPT diff = fpt_abs( left - right ); FPT d1 = safe_fpt_division( diff, fpt_abs( right ) ); FPT d2 = safe_fpt_division( diff, fpt_abs( left ) ); return m_strong_or_weak ? (d1 <= p_tolerance.get() && d2 <= p_tolerance.get()) : (d1 <= p_tolerance.get() || d2 <= p_tolerance.get()); } // Data members class p_tolerance_class { private: FPT f; public: p_tolerance_class(FPT _f=0):f(_f){}; FPT get() const{ return f;}; }; p_tolerance_class p_tolerance; private: bool m_strong_or_weak; }; template inline bool IsEqual(T x, T y) { static close_at_tolerance comp( std::numeric_limits::epsilon()/2*10); return comp(fpt_abs(x),fpt_abs(y)); }; template inline bool IsEmptyInterval(T x, T y) { return ( x>=y || IsEqual(x,y) ); } }; template size_t TLineApproximator::Shrink( size_t nDesiredPoints, size_t nTol, T eTolRight, size_t nMaxIter) { if (m_cPoints.size()<2) return 0; // number of points wanted... T dWantedPoints= __min(m_cPoints.size(), __max(2, nDesiredPoints)); T uMinWantedPoints = __min(m_cPoints.size(), __max(2, nDesiredPoints-nTol )); T uMaxWantedPoints = __min(m_cPoints.size(), __max(2, nDesiredPoints+nTol )); T eLeft, eRight, eMiddle; T dResultLeft, dResultRight; size_t iter=0; // compute limits ComputeBoundingBox(); // normalize if needed if (m_bNormalization) NormalizePoints(); // first estimation eLeft = 0; SetTol(eLeft); ComputeKeys(); dResultLeft = m_cKeys.size(); iter++; // test if success if ( (m_cKeys.size()<=uMaxWantedPoints) && (m_cKeys.size() >= uMinWantedPoints) ) goto PostProcess; // second estimation if (eTolRight<=0) eRight=__max( m_limits.GetWidth(), m_limits.GetHeight()); else eRight=eTolRight; SetTol(eRight); ComputeKeys(); dResultRight = m_cKeys.size(); // test if optimization possible // if (dResultLeftuMaxWantedPoints) // throw _T("TLineApproximator::Shrink failed: Desired compression ratio not possible in the tolerance domain."); iter++; // test if success if ( ((m_cKeys.size()<=uMaxWantedPoints) && (m_cKeys.size() >= uMinWantedPoints)) || (dResultLeft == dResultRight) ) goto PostProcess; // main loop, dichotomy do { // test middle eMiddle=(eLeft +eRight)/2; SetTol(eMiddle); // computing new DP... ComputeKeys(); // updating... if ( (m_cKeys.size()-dWantedPoints)*( dResultLeft-dResultRight) < 0 ) { eRight=eMiddle; dResultRight=m_cKeys.size(); } else { eLeft=eMiddle; dResultLeft=m_cKeys.size(); } iter++; } while ( ((m_cKeys.size()>uMaxWantedPoints) || (m_cKeys.size() < uMinWantedPoints)) /* checking that we are in the acceptable compression */ && !priv::IsEmptyInterval(eLeft,eRight) /* interval is non empty */ && (dResultRight != dResultLeft) && iter void TLineApproximator::Simplify() { if (m_cPoints.size()<2) return; // compute limits ComputeBoundingBox(); // preprocess... if (m_bNormalization) NormalizePoints(); ComputeKeys(); if (m_bNormalization) DeNormalizePoints(); } }; // namespace hull #endif // !defined(AFX_LINEAPPROXIMATOR_H__F5E6E8DC_1185_4AC0_A061_7B3309700E9D__INCLUDED_) DPHull.h -------- #if !defined(AFX_DPHULL1_H__6CE88E63_3AC7_4E18_87FB_CACF5BE62BE4__INCLUDED_) #define AFX_DPHULL1_H__6CE88E63_3AC7_4E18_87FB_CACF5BE62BE4__INCLUDED_ #if _MSC_VER > 1000 #pragma once #endif // _MSC_VER > 1000 #ifndef UINT #define UINT unsigned int #endif #include #include #include #include "PathHull.h" #include "KeyExporter.h" #include "Containers.h" namespace hull { /*! \brief Douglas-Peukler Appromixation algorithm \ingroup LAGroup */ template class TDPHull : public TLineApproximator { public: //! Build step types enum EBuildStep { //! Output to vertex BuildStepOutputVertex, //! Call DP BuildStepDP, //! Call Build BuildStepBuild, //! Is a return key BuildStepReturnKey }; //! A build step structure struct SBuildStep { SBuildStep(typename TPointContainer::const_iterator _i,typename TPointContainer::const_iterator _j, EBuildStep _s):i(_i),j(_j),s(_s){}; typename TPointContainer::const_iterator i; typename TPointContainer::const_iterator j; EBuildStep s; }; public: //! \name Constructors //@{ //! Default constructor explicit TDPHull(){}; //! Destructor virtual ~TDPHull(){}; //@} protected: //! A path hull typedef TPathHull PathHull; typedef std::stack< SBuildStep > BuildStack; //! Computes the keys virtual void ComputeKeys(); //! \name Hull methods //@{ /*! \brief Adds a function call to the stack \param i left point iterator \param j right point iterator \param buildStep step description */ void AddBuildStep( typename TPointContainer::const_iterator i, typename TPointContainer::const_iterator j, EBuildStep buildStep) { m_stack.push( BuildStack::value_type(i,j,buildStep) ); } /*! \brief Apply Douglas-Peucker algo \pre m_stack not empty \pre m_stack.top().s == BuildStepDP */ void DP(); /*! \brief Builds the path hull \pre m_stack not empty \pre m_stack.top().s == BuildStepBuild */ void Build(); /*! \brief Stores key \pre m_stack size = 2 \pre m_stack.top().s == BuildStepReturnKey \pre m_stack.top()(twice).s == BuildStepOutputVertex */ void OutputVertex() { ASSERT(!m_stack.empty()); ASSERT(m_stack.top().s==BuildStepReturnKey); GetKeys().push_back(m_stack.top().i); m_stack.pop(); ASSERT(!m_stack.empty()); ASSERT(m_stack.top().s==BuildStepOutputVertex); m_stack.pop(); }; //@} protected: //! \name Attributes //@{ TPathHull m_phRight; TPathHull m_phLeft; typename TPointContainer::const_iterator m_pPHtag; BuildStack m_stack; //@} }; template void TDPHull::DP() { T ld, rd, len_sq; SHomog l; register TPointContainer::const_iterator le; register TPointContainer::const_iterator re; ASSERT( !m_stack.empty() ); ASSERT( m_stack.top().s == BuildStepDP ); TPointContainer::const_iterator i(m_stack.top().i); TPointContainer::const_iterator j(m_stack.top().j); m_stack.pop(); CrossProduct(i, j, l); len_sq = l.x * l.x + l.y * l.y; if (j - i < 8) { /* chain small */ rd = 0.0; for (le = i + 1; le < j; ++le) { ld = DotProduct(le, l); if (ld < 0) ld = - ld; if (ld > rd) { rd = ld; re = le; } } if (rd * rd > GetTol() * len_sq) { AddBuildStep( re, j, BuildStepDP ); AddBuildStep( i, re, BuildStepOutputVertex ); AddBuildStep( i, re, BuildStepDP ); return; // OutputVertex(DP(i, re)); // return(DP(re, j)); } else { AddBuildStep(j,j,BuildStepReturnKey); return; // return j; } } else { /* chain large */ int sbase, sbrk, mid, lo, m1, brk, m2, hi; T d1, d2; if ((m_phLeft.GetTop() - m_phLeft.GetBot()) > 8) { /* left hull large */ lo = m_phLeft.GetBot(); hi = m_phLeft.GetTop() - 1; sbase = m_phLeft.SlopeSign(hi, lo, l); do { brk = (lo + hi) / 2; if (sbase == (sbrk = m_phLeft.SlopeSign(brk, brk+1, l))) if (sbase == (m_phLeft.SlopeSign(lo, brk+1, l))) lo = brk + 1; else hi = brk; } while (sbase == sbrk && lo < hi); m1 = brk; while (lo < m1) { mid = (lo + m1) / 2; if (sbase == (m_phLeft.SlopeSign(mid, mid+1, l))) lo = mid + 1; else m1 = mid; } m2 = brk; while (m2 < hi) { mid = (m2 + hi) / 2; if (sbase == (m_phLeft.SlopeSign(mid, mid+1, l))) hi = mid; else m2 = mid + 1; }; if ((d1 = DotProduct(m_phLeft.GetpElt(lo), l)) < 0) d1 = - d1; if ((d2 = DotProduct(m_phLeft.GetpElt(m2), l)) < 0) d2 = - d2; ld = (d1 > d2 ? (le = m_phLeft.GetpElt(lo), d1) : (le = m_phLeft.GetpElt(m2), d2)); } else { /* Few SPoints in left hull */ ld = 0.0; for (mid = m_phLeft.GetBot(); mid < m_phLeft.GetTop(); mid++) { if ((d1 = DotProduct(m_phLeft.GetpElt(mid), l)) < 0) d1 = - d1; if (d1 > ld) { ld = d1; le = m_phLeft.GetpElt(mid); } } } if ((m_phRight.GetTop() - m_phRight.GetBot()) > 8) { /* right hull large */ lo = m_phRight.GetBot(); hi = m_phRight.GetTop() - 1; sbase = m_phRight.SlopeSign(hi, lo, l); do { brk = (lo + hi) / 2; if (sbase == (sbrk = m_phRight.SlopeSign(brk, brk+1, l))) if (sbase == (m_phRight.SlopeSign(lo, brk+1, l))) lo = brk + 1; else hi = brk; } while (sbase == sbrk && lo < hi); m1 = brk; while (lo < m1) { mid = (lo + m1) / 2; if (sbase == (m_phRight.SlopeSign(mid, mid+1, l))) lo = mid + 1; else m1 = mid; } m2 = brk; while (m2 < hi) { mid = (m2 + hi) / 2; if (sbase == (m_phRight.SlopeSign(mid, mid+1, l))) hi = mid; else m2 = mid + 1; }; if ((d1 = DotProduct(m_phRight.GetpElt(lo), l)) < 0) d1 = - d1; if ((d2 = DotProduct(m_phRight.GetpElt(m2), l)) < 0) d2 = - d2; rd = (d1 > d2 ? (re = m_phRight.GetpElt(lo), d1) : (re = m_phRight.GetpElt(m2), d2)); } else { /* Few SPoints in righthull */ rd = 0.0; for (mid = m_phRight.GetBot(); mid < m_phRight.GetTop(); mid++) { if ((d1 = DotProduct(m_phRight.GetpElt(mid), l)) < 0) d1 = - d1; if (d1 > rd) { rd = d1; re = m_phRight.GetpElt(mid); } } } } if (ld > rd) if (ld * ld > GetTol() * len_sq) { /* split left */ register int tmpo; while ((m_phLeft.GetHp() >= 0) && ( (tmpo = m_phLeft.GetOps()[m_phLeft.GetHp()] ), ((re = m_phLeft.GetpHelt(m_phLeft.GetHp())) != le) || (tmpo != PathHull::StackPushOp))) { m_phLeft.DownHp(); switch (tmpo) { case PathHull::StackPushOp: m_phLeft.DownTop(); m_phLeft.UpBot(); break; case PathHull::StackTopOp: m_phLeft.UpTop(); m_phLeft.SetTopElt(re); break; case PathHull::StackBotOp: m_phLeft.DownBot(); m_phLeft.SetBotElt(re); break; } } AddBuildStep( le, j, BuildStepDP ); AddBuildStep( le, j, BuildStepBuild); AddBuildStep( i, le, BuildStepOutputVertex); AddBuildStep( i, le, BuildStepDP); AddBuildStep( i, le, BuildStepBuild); return; // Build(i, le); // OutputVertex(DP(i, le)); // Build(le, j); // return DP(le, j); } else { AddBuildStep(j,j,BuildStepReturnKey); return; // return(j); } else /* extreme on right */ if (rd * rd > GetTol() * len_sq) { /* split right or both */ // if (m_pPHtag == re) // { // AddBuildStep( i, re, BuildStepBuild); // Build(i, re); // } // else if (m_pPHtag != re) { /* split right */ register int tmpo; while ((m_phRight.GetHp() >= 0) && ((tmpo = m_phRight.GetOps()[m_phRight.GetHp()]), ((le = m_phRight.GetpHelt(m_phRight.GetHp())) != re) || (tmpo != PathHull::StackPushOp))) { m_phRight.DownHp(); switch (tmpo) { case PathHull::StackPushOp: m_phRight.DownTop(); m_phRight.UpBot(); break; case PathHull::StackTopOp: m_phRight.UpTop(); m_phRight.SetTopElt(le); break; case PathHull::StackBotOp: m_phRight.DownBot(); m_phRight.SetBotElt(le); break; } } } AddBuildStep( re, j ,BuildStepDP ); AddBuildStep( re, j, BuildStepBuild ); AddBuildStep( i, re, BuildStepOutputVertex ); AddBuildStep( i, re, BuildStepDP ); if (m_pPHtag == re) AddBuildStep( i, re, BuildStepBuild); return; // OutputVertex(DP(i, re)); // Build(re, j); // return(DP(re, j)); } else AddBuildStep( j,j, BuildStepReturnKey); // return(j); } template void TDPHull::Build() { TPointContainer::const_iterator k; int topflag, botflag; ASSERT( !m_stack.empty() ); ASSERT( m_stack.top().s == BuildStepBuild ); TPointContainer::const_iterator i(m_stack.top().i); TPointContainer::const_iterator j(m_stack.top().j); m_stack.pop(); m_pPHtag = i + (j - i) / 2; /* Assign tag vertex */ m_phLeft.Init(m_pPHtag, m_pPHtag - 1); /* \va{left} hull */ for (k = m_pPHtag - 2; k >= i; --k) { topflag = m_phLeft.LeftOfTop(k); botflag = m_phLeft.LeftOfBot(k); if ((topflag || botflag) && !(topflag && botflag)) { while (topflag) { m_phLeft.PopTop(); topflag = m_phLeft.LeftOfTop(k); } while (botflag) { m_phLeft.PopBot(); botflag = m_phLeft.LeftOfBot(k); } m_phLeft.Push(k); } } m_phRight.Init(m_pPHtag, m_pPHtag + 1); /* \va{right} hull */ for (k = m_pPHtag + 2; k <= j; ++k) { topflag = m_phRight.LeftOfTop(k); botflag = m_phRight.LeftOfBot(k); if ((topflag || botflag) && !(topflag && botflag)) { while (topflag) { m_phRight.PopTop(); topflag = m_phRight.LeftOfTop(k); } while (botflag) { m_phRight.PopBot(); botflag = m_phRight.LeftOfBot(k); } m_phRight.Push(k); } } }; template void TDPHull::ComputeKeys() { using namespace std; static const T epsilon2 = numeric_limits::epsilon()*numeric_limits::epsilon(); TLineApproximator::ComputeKeys(); const TPointContainer& pc=GetPoints(); TPointContainer::const_iterator pcend=pc.end(); --pcend; T len_sq; SHomog l; ///////////////////////////////////////////////////////////////////////////// CrossProduct(pc.begin(), pcend, l); len_sq = l.x * l.x + l.y * l.y; if (len_sq < epsilon2) throw _T("TDPHull::DP failed: Start and end points are equal or at a distance < epsilon\n"); //////////////////////////////////////////////////////////////////////// // prepraring path if needed... m_phLeft.SetMaxSize(pc.size()+1); m_phRight.SetMaxSize(pc.size()+1); ///////////////////////////////////////////////////////////////////////// // building hull // Build(pc.begin(), pcend); /* Build the initial path hull */ // OutputVertex( pc.begin() ); // OutputVertex( DP(pc.begin(), pcend) ); /* Simplify */ AddBuildStep( pc.begin(), pcend, BuildStepBuild ); Build(); AddBuildStep( pc.begin(), pc.begin(), BuildStepOutputVertex ); AddBuildStep( pc.begin(), pc.begin(), BuildStepReturnKey ); OutputVertex(); AddBuildStep( pc.begin(), pc.begin(), BuildStepOutputVertex ); AddBuildStep( pc.begin(), pcend, BuildStepDP ); while (!m_stack.empty()) { // std::cerr<<"stack size: "<> - KeyContainer: list \ingroup LAGroup */ typedef TDPHull >, std::vector< std::vector< TPoint< float > >::const_iterator > > CDPHullF; /*! \brief A double precision DPHull The classical DPHull object: - PointContainer: vector> - KeyContainer: list \ingroup LAGroup */ typedef TDPHull >, std::vector< std::vector< TPoint< double > >::const_iterator > > CDPHullD; }; #endif // !defined(AFX_DPHULL1_H__6CE88E63_3AC7_4E18_87FB_CACF5BE62BE4__INCLUDED_) PathHull.h ---------- // PathHull.h: interface for the CPathHull class. // ////////////////////////////////////////////////////////////////////// #if !defined(AFX_PATHHULL_H__50C639BA_585B_4272_9AF4_4632128D8938__INCLUDED_) #define AFX_PATHHULL_H__50C639BA_585B_4272_9AF4_4632128D8938__INCLUDED_ #if _MSC_VER > 1000 #pragma once #endif // _MSC_VER > 1000 #include "LineApproximator.h" namespace hull { #define DP_SGN(a) (a >= 0) /*! \brief A path \ingroup */ template class TPathHull { public: enum EStackOp { StackPushOp=0, StackTopOp=1, StackBotOp=2 }; typedef std::vector OpContainer; typedef std::vector PCItContainer; TPathHull(): m_iHullMax(0) {}; virtual ~TPathHull() {}; void SetMaxSize(int iHullMax); int GetHp() const { return m_iHp;}; int GetBot() const { return m_iBot;}; int GetTop() const { return m_iTop;}; typename const TPointContainer::const_iterator& GetpElt(int i) const { ASSERT(i=0); ASSERT(m_iTop=0); ASSERT(m_iBot= 0) && ((tmpo = m_pOp[m_iHp]), ((tmpe = m_ppHelt[m_iHp]) != e) || (tmpo != StackPushOp))) { m_iHp--; switch (tmpo) { case StackPushOp: m_iTop--; m_iBot++; break; case StackTopOp: ASSERT(m_iTop-1>=0); ASSERT(m_iTop+1=0); ASSERT(m_iBot-1::SHomog& line, typename TPointContainer::const_iterator* e, T& dist) { int sbase, sbrk, mid,lo, m1, brk, m2, hi; T d1, d2; if ((m_iTop - m_iBot) > 8) { lo = m_iBot; hi = m_iTop - 1; sbase = SlopeSign(hi, lo, line); do { brk = (lo + hi) / 2; if (sbase == (sbrk = SlopeSign(brk, brk+1, line))) if (sbase == (SlopeSign(lo, brk+1, line))) lo = brk + 1; else hi = brk; } while (sbase == sbrk); m1 = brk; while (lo < m1) { mid = (lo + m1) / 2; if (sbase == (SlopeSign(mid, mid+1, line))) lo = mid + 1; else m1 = mid; } m2 = brk; while (m2 < hi) { mid = (m2 + hi) / 2; if (sbase == (SlopeSign(mid, mid+1, line))) hi = mid; else m2 = mid + 1; } ASSERT(lo>=0); ASSERT(lo ::DotProduct(*m_ppElt[lo], line)) < 0) d1 = - d1; ASSERT(m2>=0); ASSERT(m2 ::DotProduct(*m_ppElt[m2], line)) < 0) d2 = - d2; dist = (d1 > d2 ? (*e = m_ppElt[lo], d1) : (*e = m_ppElt[m2], d2)); } else /* Few DP_POINTs in hull */ { dist = 0.0; for (mid = m_iBot; mid < m_iTop; mid++) { ASSERT(mid>=0); ASSERT(midsize()); if ((d1 = TLine::::DotProduct(*m_ppElt[mid], line)) < 0) d1 = - d1; if (d1 > *dist) { dist = d1; *e = m_ppElt[mid]; } } } } void Init(typename const TPointContainer::const_iterator& e1, typename const TPointContainer::const_iterator& e2) { /* Initialize path hull and history */ ASSERT(m_iHullMax>=0); ASSERT(m_iHullMax+1= 0); ASSERT(m_iTop+1 < m_ppElt.size()); ASSERT(m_iBot-1 >= 0); ASSERT(m_iBot-1 < m_ppElt.size()); ASSERT(m_iHp+1 >= 0); ASSERT(m_iHp+1 < m_ppHelt.size()); ASSERT(m_iHp+1 < m_pOp.size()); /* Push element $e$ onto path hull $h$ */ m_ppElt[++m_iTop] = m_ppElt[--m_iBot] = m_ppHelt[++m_iHp] = e; m_pOp[m_iHp] = StackPushOp; } void PopTop() { ASSERT(m_iTop >= 0); ASSERT(m_iTop < m_ppElt.size()); ASSERT(m_iHp+1 >= 0); ASSERT(m_iHp+1 < m_ppHelt.size()); ASSERT(m_iHp+1 < m_pOp.size()); m_ppHelt[++m_iHp] = m_ppElt[m_iTop--]; m_pOp[m_iHp] = StackTopOp; } void PopBot() { ASSERT(m_iBot >= 0); ASSERT(m_iBot < m_ppElt.size()); ASSERT(m_iHp+1 >= 0); ASSERT(m_iHp+1 < m_ppHelt.size()); ASSERT(m_iHp+1 < m_pOp.size()); /* Pop from bottom */ m_ppHelt[++m_iHp] = m_ppElt[m_iBot++]; m_pOp[m_iHp] = StackBotOp; } void Add(typename const TPointContainer::const_iterator& p) { int topflag, botflag; topflag = LeftOfTop(p); botflag = LeftOfBot(p); if (topflag || botflag) { while (topflag) { PopTop(); topflag = LeftOfTop(p); } while (botflag) { PopBot(); botflag = LeftOfBot(p); } Push(p); } } int LeftOfTop(typename const TPointContainer::const_iterator& c) { ASSERT(m_iTop >= 1); ASSERT(m_iTop < m_ppElt.size()); /* Determine if point c is left of line a to b */ return (((*m_ppElt[m_iTop]).x - (*c).x)*((*m_ppElt[m_iTop-1]).y - (*c).y) >= ((*m_ppElt[m_iTop-1]).x - (*c).x)*((*m_ppElt[m_iTop]).y - (*c).y)); } int LeftOfBot(typename const TPointContainer::const_iterator& c) { ASSERT(m_iBot >= 0); ASSERT(m_iBot+1 < m_ppElt.size()); /* Determine if point c is left of line a to b */ return (((*m_ppElt[m_iBot+1]).x - (*c).x)*((*m_ppElt[m_iBot]).y - (*c).y) >= ((*m_ppElt[m_iBot]).x - (*c).x)*((*m_ppElt[m_iBot+1]).y - (*c).y)); } int SlopeSign(int p, int q, typename const TLine::SHomog& l) { ASSERT(p >= 0); ASSERT(p < m_ppElt.size()); ASSERT(q >= 0); ASSERT(q < m_ppElt.size()); /* Return the sign of the projection of $h[q] - h[p]$ onto the normal to line $l$ */ return (int) (DP_SGN( (l.x)*((*m_ppElt[q]).x - (*m_ppElt[p]).x) + (l.y)*((*m_ppElt[q]).y - (*m_ppElt[p]).y) ) ) ; }; protected: /// Maxium number of elements in hull int m_iHullMax; /// internal values int m_iTop; int m_iBot; int m_iHp; OpContainer m_pOp; PCItContainer m_ppElt; PCItContainer m_ppHelt; }; template void TPathHull::SetMaxSize(int iHullMax) { if (m_iHullMax == iHullMax) return; m_iHullMax=iHullMax; m_pOp.resize(3*m_iHullMax); m_ppElt.resize(2*m_iHullMax); m_ppHelt.resize(3*m_iHullMax); } }; #endif // !defined(AFX_PATHHULL_H__50C639BA_585B_4272_9AF4_4632128D8938__INCLUDED_) Containers.h ------------ // Containers.h: interface for the CContainers class. // ////////////////////////////////////////////////////////////////////// #if !defined(AFX_CONTAINERS_H__33EAD324_F802_4BC8_BEC8_39E69C1C21A7__INCLUDED_) #define AFX_CONTAINERS_H__33EAD324_F802_4BC8_BEC8_39E69C1C21A7__INCLUDED_ #if _MSC_VER > 1000 #pragma once #endif // _MSC_VER > 1000 #include #include namespace hull { /*! \defgroup DCGroup Double container groups \ingroup LAGroup */ /*! \brief Virtual base class for Point double container \ingroup DCGroup */ template class TPointDoubleContainerBase { public: //! \name Typedefs //@{ typedef TPoint value_type; typedef TPointRef reference; typedef TVectorX container_x; typedef TVectorY container_y; //@} /*! \brief Constructor \param pX pointer to x coordinate container, \param pY pointer to y coordinate container */ TPointDoubleContainerBase(container_x* pX = NULL, container_y* pY =NULL):m_pX(pX),m_pY(pY){}; virtual ~TPointDoubleContainerBase(){}; //! return the size of the point container size_t size() const { ASSERT(m_pX); ASSERT(m_pY); return __min( m_pX->size(), m_pY->size());}; /*! \brief resize the container \param size the new size of the vector. */ void resize(size_t size) { ASSERT(m_pX); ASSERT(m_pY); m_pX->resize(size); m_pY->resize(size);}; //! return the value at position i value_type operator[](UINT i) const { return value_type((*m_pX)[i],(*m_pY)[i]);}; //! return a reference to position i reference operator[](UINT i) { return reference((*m_pX)[i],(*m_pY)[i]);}; //! Sets the container pointers void SetContainers( container_x* pX, container_y* pY) { m_pX=pX; m_pY=pY;}; //! return the x coordinate pointer, const const container_x* GetXContainer() const { return m_pX;}; //! return the y coordinate pointer, const const container_y* GetYContainer() const { return m_pY;}; //! return the x coordinate pointer container_x* GetXContainer() { return m_pX;}; //! return the y coordinate pointer container_y* GetYContainer() { return m_pY;}; protected: container_x* m_pX; container_y* m_pY; }; /*! \brief Base class for point iterator \param T float or double \param TVectorX x coordinate container with random access iterator \param TVectorY y coordinate container with random access iterator A random access iterator base class. \ingroup DCGroup */ template class TPointIt { public: TPointIt(const TPointDoubleContainerBase* pV = NULL, UINT index = 0):m_pV(pV),m_index(index){}; virtual ~TPointIt(){}; TPointIt& operator = (const TPointIt& t) { if (&t!=this) { m_pV=t.m_pV; m_index=t.m_index; }; return *this; }; friend UINT operator - (const TPointIt& t1, const TPointIt& t2){ return t1.m_index-t2.m_index; }; friend bool operator == ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index==t2.m_index && t1.m_pV==t2.m_pV;}; friend bool operator != ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index!=t2.m_index || t1.m_pV!=t2.m_pV;}; friend bool operator < ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index>t2.m_index;}; friend bool operator <= ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index<=t2.m_index;}; friend bool operator >= ( const TPointIt& t1, const TPointIt& t2) { return t1.m_index>=t2.m_index;}; protected: long m_index; const TPointDoubleContainerBase* m_pV; }; /*! \brief PointDoubleContainer iterator \param T float or double \param TVectorX x coordinate container with random access iterator \param TVectorY y coordinate container with random access iterator A random access iterator. \ingroup DCGroup */ template class TPointRandIt : public TPointIt { public: TPointRandIt(const TPointDoubleContainerBase* pV = NULL, UINT index = 0):TPointIt(pV,index) {}; TPointRandIt& operator = (const TPointRandIt& t) { if (&t!=this) { TPointIt::operator=(t); }; return *this; }; TPoint operator*() const { ASSERT(m_pV); ASSERT(m_indexsize()); return TPoint((*m_pV->GetXContainer())[m_index], (*m_pV->GetYContainer())[m_index]); }; TPointRef operator*() { ASSERT(m_pV); ASSERT(m_indexsize()); return TPointRef( (*m_pV->GetXContainer())[m_index], (*m_pV->GetYContainer())[m_index]); }; TPointRandIt& operator++(int) { return TPointRandIt( m_pV, m_index+1); }; TPointRandIt& operator--(int) { return TPointRandIt( m_pV, m_index-1); }; TPointRandIt& operator++() { m_index++; return *this; }; TPointRandIt& operator--() { m_index--; return *this; }; TPointRandIt& operator+=(UINT i) { m_index+=i; return *this; }; TPointRandIt& operator-=(UINT i) { m_index-=i; return *this; }; friend TPointRandIt operator + (const TPointRandIt& t, UINT i) { return TPointRandIt( t.m_pV, t.m_index+i);}; friend TPointRandIt operator - (const TPointRandIt& t, UINT i) { return TPointRandIt( t.m_pV, t.m_index-i);}; }; /*! \brief PointDoubleContainer const_iterator \param T float or double \param TVectorX x coordinate container with random access iterator \param TVectorY y coordinate container with random access iterator A const random access iterator. \ingroup DCGroup */ template class TPointConstRandIt : public TPointIt { public: TPointConstRandIt(const TPointDoubleContainerBase* pV = NULL, UINT index = 0):TPointIt(pV,index){}; TPointConstRandIt& operator = (const TPointConstRandIt& t) { if (&t!=this) { TPointIt::operator=(t); }; return *this; }; TPointConstRandIt& operator = (const TPointRandIt& t) { TPointIt::operator=(t); return *this; }; TPoint operator*() const { ASSERT(m_pV); ASSERT(m_indexsize()); return TPoint((*m_pV->GetXContainer())[m_index], (*m_pV->GetYContainer())[m_index]); }; TPointConstRandIt& operator++(int) { return TPointConstRandIt( t.m_pV, m_index+1); }; TPointConstRandIt& operator--(int) { return TPointConstRandIt( t.m_pV, m_index-1); }; TPointConstRandIt& operator++() { m_index++; return *this; }; TPointConstRandIt& operator--() { m_index--; return *this; }; TPointConstRandIt& operator+=(UINT i) { m_index+=i; return *this; }; TPointConstRandIt& operator-=(UINT i) { m_index-=i; return *this; }; friend TPointConstRandIt operator + (const TPointConstRandIt& t, UINT i) { return TPointConstRandIt( t.m_pV, t.m_index+i);}; friend TPointConstRandIt operator - (const TPointConstRandIt& t, UINT i) { return TPointConstRandIt( t.m_pV, t.m_index-i);}; }; /*! \brief A container linking two separate containers into a point container \param T float or double \param TVectorX x coordinate container with random access iterator \param TVectorY y coordinate container with random access iterator \ingroup DCGroup */ template class TPointDoubleContainer : virtual public TPointDoubleContainerBase { public: TPointDoubleContainer(TVectorX* pX = NULL, TVectorY* pY =NULL):TPointDoubleContainerBase(pX,pY){}; virtual~TPointDoubleContainer(){}; typedef TPointConstRandIt const_iterator; typedef TPointRandIt iterator; iterator begin() { return iterator(this,0); }; iterator end() { return iterator(this,size()); }; const_iterator begin() const { return const_iterator(this,0); }; const_iterator end() const { return const_iterator(this,size()); }; }; /*! \brief A container to export point to two containers \param T float or double \param TListX x coordinate container with single direction iterator \param TListY y coordinate container with single direction iterator \param TPointContainer The point container \ingroup DCGroup */ template class TKeyDoubleContainer { public: typedef typename TPointContainer::const_iterator value_type; typedef TListX container_x; typedef TListY container_y; TKeyDoubleContainer( container_x* pListX = NULL, container_y* pListY = NULL):m_pListX(pListX), m_pListY(pListY){}; void SetContainers( container_x* pListX, container_y* pListY) { m_pListX=pListX; m_pListY=pListY;}; container_x* GetXContainer() { return m_pListX;}; container_y* GetYContainer() { return m_pListY;}; const container_x* GetXContainer() const { return m_pListX;}; const container_y* GetYContainer() const { return m_pListY;}; void clear() { ASSERT(m_pListX); ASSERT(m_pListY); m_pListX->clear(); m_pListY->clear();}; size_t size() const { ASSERT(m_pListX); ASSERT(m_pListY); return __min( m_pListX->size(), m_pListY->size());}; void push_back( const value_type& p) { ASSERT(m_pListX); ASSERT(m_pListY); m_pListX->push_back((*p).x); m_pListY->push_back((*p).y);}; void push_front( const value_type& p) { ASSERT(m_pListX); ASSERT(m_pListY); m_pListX->push_front((*p).x); m_pListY->push_front((*p).y);}; protected: container_x* m_pListX; container_y* m_pListY; }; }; #endif // !defined(AFX_CONTAINERS_H__33EAD324_F802_4BC8_BEC8_39E69C1C21A7__INCLUDED_)
 Confused ashnyr25-Sep-03 22:48 ashnyr 25-Sep-03 22:48
 another implementation faraz05-Aug-03 2:00 faraz0 5-Aug-03 2:00
 Re: another implementation Jonathan de Halleux5-Aug-03 5:24 Jonathan de Halleux 5-Aug-03 5:24
 Well done Bitterman4-Mar-03 13:19 Bitterman 4-Mar-03 13:19
 SQL Jonathan de Halleux5-Mar-03 8:14 Jonathan de Halleux 5-Mar-03 8:14
 Re: SQL Carsten Breum21-Mar-03 1:44 Carsten Breum 21-Mar-03 1:44
 Diving on hold Jonathan de Halleux27-Mar-03 6:43 Jonathan de Halleux 27-Mar-03 6:43
 Re: Diving on hold Carsten Breum27-Mar-03 20:30 Carsten Breum 27-Mar-03 20:30
 Re: Diving on hold Jonathan de Halleux27-Mar-03 22:18 Jonathan de Halleux 27-Mar-03 22:18
 Re: Diving on hold Ceox14-Oct-03 23:37 Ceox 14-Oct-03 23:37
 Re: SQL Jonathan de Halleux28-Jul-03 13:26 Jonathan de Halleux 28-Jul-03 13:26
 Examples Chopper4-Mar-03 2:53 Chopper 4-Mar-03 2:53
 Re: Examples Corey W4-Mar-03 4:27 Corey W 4-Mar-03 4:27
 Re: Examples Chopper5-Mar-03 4:46 Chopper 5-Mar-03 4:46
 Sick datatypes Jonathan de Halleux12-Mar-03 7:27 Jonathan de Halleux 12-Mar-03 7:27
 Re: Sick datatypes Corey W12-Mar-03 7:34 Corey W 12-Mar-03 7:34
 Cool Jonathan de Halleux13-Mar-03 0:46 Jonathan de Halleux 13-Mar-03 0:46
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Article Copyright 2002 by Jonathan de Halleux