kicad/polygon/SutherlandHodgmanClipPoly.h

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/********************************************************************************
* Copyright (C) 2004 Sjaak Priester
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This file is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Tinter; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
********************************************************************************/
// SutherlandHodgman
// Class to perform polygon clipping against an upright rectangular boundary window.
// Implementation of Sutherland-Hodgman algorithm (1974).
//
// Version 1.0 (C) 2004, Sjaak Priester, Amsterdam.
// mailto:sjaak@sjaakpriester.nl
// http://www.sjaakpriester.nl
#ifndef __SUTHERLAND_HODGMAN_H__
#define __SUTHERLAND_HODGMAN_H__
#include <vector>
#include <functional>
#ifndef _GDIPLUS_H
// I designed this with GDI+ in mind. However, this particular code doesn't
// use GDI+ at all, only some of it's variable types.
// These definitions are substitutes for those of GDI+.
typedef double REAL;
class PointF
{
public:
REAL X;
REAL Y;
PointF() : X( 0 )
, Y( 0 ) { }
PointF( const PointF& p ) : X( p.X )
, Y( p.Y ) { }
PointF( REAL x, REAL y ) : X( x )
, Y( y ) { }
PointF operator+( const PointF& p ) const { return PointF( X + p.X, Y + p.Y ); }
PointF operator-( const PointF& p ) const { return PointF( X - p.X, Y - p.Y ); }
bool Equals( const PointF& p ) { return (X == p.X) && (Y == p.Y); }
};
class RectF
{
public:
REAL X;
REAL Y;
REAL Width;
REAL Height;
RectF() { X = 0, Y = 0, Height = 0, Width = 0; }
RectF( const RectF& r )
{
X = r.X; Y = r.Y; Height = r.Height, Width = r.Width;
}
RectF( REAL x, REAL y, REAL w, REAL h ) : X( x ), Y( y ),Width( w ), Height( h )
{ }
REAL GetLeft() const { return X; }
REAL GetTop() const { return Y; }
REAL GetRight() const { return X + Width; }
REAL GetBottom() const { return Y + Height; }
};
#endif // _GDIPLUS_H
typedef std::vector<PointF> pointVector;
typedef std::vector<PointF>::iterator pointIterator;
typedef std::vector<PointF>::const_iterator cpointIterator;
class SutherlandHodgman
{
public:
// Constructor. Parameter is the boundary rectangle.
// SutherlandHodgman expects a 'normalized' boundary rectangle, meaning
// that boundaries.GetRight() > boundaries.GetLeft() and
// boundaries.GetBottom() > boundaries.GetTop().
// In other words: boundary.Width > 0 and boundaries.Height > 0.
// If this is violated, nothing will be output.
SutherlandHodgman( RectF& boundaries ) :
m_stageBottom( m_stageOut, boundaries.GetBottom() )
, /* Initialize each stage */ m_stageLeft( m_stageBottom, boundaries.GetLeft() )
, /* with its next stage and */ m_stageTop( m_stageLeft, boundaries.GetTop() )
, /* the boundary position. */ m_stageRight( m_stageTop, boundaries.GetRight() )
{
}
void Clip( pointVector& input, pointVector& clipped )
{
clipped.clear();
m_stageOut.SetDestination( &clipped );
// Clip each input vertex.
for( cpointIterator it = input.begin(); it != input.end(); ++it )
m_stageRight.HandleVertex( *it );
// Do the final step.
m_stageRight.Finalize();
}
private:
// Implementation of a horizontal boundary (top or bottom).
// Comp is a std::binary_function object, comparing its two parameters, f.i. std::less.
template <class Comp>
class BoundaryHor
{
public:
BoundaryHor( REAL y ) : m_Y( y ) { }
bool IsInside( const PointF& pnt ) const
{
return Comp ()( pnt.Y, m_Y );
} // return true if pnt.Y is at the inside of the boundary
PointF Intersect( const PointF& p0, const PointF& p1 ) const // return intersection point of line p0...p1 with boundary
{ // assumes p0...p1 is not strictly horizontal
PointF d = p1 - p0;
REAL xslope = d.X / d.Y;
PointF r;
r.Y = m_Y;
r.X = p0.X + xslope * (m_Y - p0.Y);
return r;
}
private:
REAL m_Y;
};
// Implementation of a vertical boundary (left or right).
template <class Comp>
class BoundaryVert
{
public:
BoundaryVert( REAL x ) : m_X( x )
{ }
bool IsInside( const PointF& pnt ) const
{
return Comp() ( pnt.X, m_X );
}
PointF Intersect( const PointF& p0, const PointF& p1 ) const // assumes p0...p1 is not strictly vertical
{
PointF d = p1 - p0;
REAL yslope = d.Y / d.X;
PointF r;
r.X = m_X;
r.Y = p0.Y + yslope * (m_X - p0.X);
return r;
}
private:
REAL m_X;
};
// This template class is the workhorse of the algorithm. It handles the clipping against one boundary.
// Boundary is either BoundaryHor or BoundaryVert, Stage is the next ClipStage, or the output stage.
template <class Boundary, class Stage>
class ClipStage : private Boundary
{
public:
ClipStage( Stage& nextStage, REAL position ) :
Boundary( position ) , m_NextStage( nextStage ), m_bFirst( true )
{ }
void HandleVertex( const PointF& pntCurrent ) // Function to handle one vertex
{
bool bCurrentInside = this->IsInside( pntCurrent ); // See if vertex is inside the boundary.
if( m_bFirst ) // If this is the first vertex...
{
m_pntFirst = pntCurrent; // ... just remember it,...
m_bFirst = false;
}
else // Common cases, not the first vertex.
{
if( bCurrentInside ) // If this vertex is inside...
{
if( !m_bPreviousInside ) // ... and the previous one was outside
m_NextStage.HandleVertex( this->Intersect( m_pntPrevious, pntCurrent ) );
// ... first output the intersection point.
m_NextStage.HandleVertex( pntCurrent ); // Output the current vertex.
}
else if( m_bPreviousInside ) // If this vertex is outside, and the previous one was inside...
m_NextStage.HandleVertex( this->Intersect( m_pntPrevious, pntCurrent ) );
// ... output the intersection point.
// If neither current vertex nor the previous one are inside, output nothing.
}
m_pntPrevious = pntCurrent; // Be prepared for next vertex.
m_bPreviousInside = bCurrentInside;
}
void Finalize()
{
HandleVertex( m_pntFirst ); // Close the polygon.
m_NextStage.Finalize(); // Delegate to the next stage.
}
private:
Stage& m_NextStage; // the next stage
bool m_bFirst; // true if no vertices have been handled
PointF m_pntFirst; // the first vertex
PointF m_pntPrevious; // the previous vertex
bool m_bPreviousInside; // true if the previous vertex was inside the Boundary
};
class OutputStage
{
public:
OutputStage() : m_pDest( 0 ) { }
void SetDestination( pointVector* pDest ) { m_pDest = pDest; }
void HandleVertex( const PointF& pnt ) { m_pDest->push_back( pnt ); } // Append the vertex to the output container.
void Finalize() { } // Do nothing.
private:
pointVector* m_pDest;
};
// These typedefs define the four boundaries. In keeping up with the GDI/GDI+ interpretation of
// rectangles, we include the left and top boundaries, but not the right and bottom boundaries.
// In other words: a vertex on the left boundary is considered to be inside, but a vertex
// on the right boundary is considered to be outside.
typedef BoundaryVert<std::less<REAL> > BoundaryRight;
typedef BoundaryHor<std::greater_equal<REAL> > BoundaryTop;
typedef BoundaryVert<std::greater_equal<REAL> > BoundaryLeft;
typedef BoundaryHor<std::less<REAL> > BoundaryBottom;
// Next typedefs define the four stages. First template parameter is the boundary,
// second template parameter is the next stage.
typedef ClipStage<BoundaryBottom, OutputStage> ClipBottom;
typedef ClipStage<BoundaryLeft, ClipBottom> ClipLeft;
typedef ClipStage<BoundaryTop, ClipLeft> ClipTop;
typedef ClipStage<BoundaryRight, ClipTop> ClipRight;
// Our data members.
OutputStage m_stageOut;
ClipBottom m_stageBottom;
ClipLeft m_stageLeft;
ClipTop m_stageTop;
ClipRight m_stageRight;
};
#endif