０５年写的直线裁剪算法

头文件<line.h>

#pragma once
#include  " afx.h "
#include  " atltypes.h "
/**/ /*
 * Powered by Tauruser
 * Tauruser~gmail.com
 * Written on 2005.12
 * 欢迎转载，请说明出处
 */  
class  CLine :
     public  CObject
{
    DECLARE_SERIAL (CLine)
public:
    CLine(void);
    ~CLine(void);
private:
    CPoint m_ptFrom;
private:
    CPoint m_ptTo;
public:
    CLine(CPoint ptFrom, CPoint ptTo);
    void Draw(CDC* pDC);
    void Serialize(CArchive& ar);
    CLine* SetLine(CPoint ptFrom, CPoint ptTo);
    // 剪裁线段,参数为窗口左上角和右下角坐标,当线段在窗口内返回TRUE,否则

FALSE
    bool Cut(CPoint ptUpLeft, CPoint ptDownRight);
} ;

源码<line.cpp>

#include  " StdAfx.h "
#include  " .\line.h "
/**/ /*
 * Powered by Tauruser
 * Tauruser~gmail.com
 * Written on 2005.12
 * 欢迎转载，请说明出处
 */  
IMPLEMENT_SERIAL (CLine,CObject, 1 )
CLine::CLine( void )
: m_ptFrom( 0 )
, m_ptTo( 0 )
{
}

CLine:: ~ CLine( void )
{
}

CLine::CLine(CPoint ptFrom, CPoint ptTo)
{
    m_ptFrom=ptFrom;
    m_ptTo=ptTo;
}

void  CLine::Draw(CDC *  pDC)
{
    pDC->MoveTo(m_ptFrom);
    pDC->LineTo(m_ptTo);
}

void  CLine::Serialize(CArchive &  ar)
{
    CObject::Serialize(ar);
    if(ar.IsStoring())
        ar<<m_ptFrom<<m_ptTo;
    else
        ar>>m_ptFrom>>m_ptTo;
}

CLine *  CLine::SetLine(CPoint ptFrom, CPoint ptTo)
{
    m_ptFrom=ptFrom;
    m_ptTo=ptTo;
    return this;
}

//  剪裁线段,参数为窗口左上角和右下角坐标,当线段在窗口内返回TRUE,否则FALSE
bool  CLine::Cut(CPoint ptUpLeft, CPoint ptDownRight)
{
    //long iA,iB,iC,iD,iXl,iXr,iYt,iYb; 
    const long iA(m_ptFrom.x), iB(m_ptFrom.y), iC(m_ptTo.x), iD(m_ptTo.y);
    long iXl=ptUpLeft.x, iXr=ptDownRight.x, iYt=ptUpLeft.y, iYb=ptDownRight.y;
    int temp;
    if (iXl>iXr) 
    {
        temp=iXl;
        iXl=iXr;
        iXr=temp;
    }
    if(iYb>iYt)
    {
        temp=iYb;
        iYb=iYt;
        iYt=temp;
    }

    if(iXl<=iA && iA<=iXr)
    {
        if(iYb<=iB && iB<=iYt)
        {    ;//m_ptFrom保持原值
        }else if(iB<iYb && iD<iYb) 
            return false;//与窗口无交.
        else if (iB<iYb && iD>=iYb)
        {
            //1.2
            int x;
            x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
            if(iXl<=x && x<=iXr)//检验x的有校性
            {
                m_ptFrom.x=x;
                m_ptFrom.y=iYb;

            }else return false;//否则无交点

        }else if(iB>iYt && iD>iYt)     return false;//与窗口无交
        else if(iB>iYt && iD<=iYt)
        {    
            //1.3
            int x;
            x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
            if(iXl<=x && x<=iXr)//
            {
                m_ptFrom.x=x;
                m_ptFrom.y=iYt;
            }else return false;//否则无交点

        }
        

    }else if(iA<iXl)
    {
        if(iC<iXl) return false;
        else
        {
            int y;
            y=iB-((iA-iXl)*(iB-iD)/(iA-iC));

            if(iYb<=y && y<=iYt)
            {
                m_ptFrom.x=iXl;
                m_ptFrom.y=y;
            }else if ((y<iYb || y>iYt) && (iYb<=iB && iB<=iYt)) 
            {
                return false;
            }
            else if(y<iYb || iB<iYb)
            {
                //1.2
                int x;
                x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
                if(iXl<=x && x<=iXr)//检验x的有校性
                {
                    m_ptFrom.x=x;
                    m_ptFrom.y=iYb;
                }else return false;//否则无交点
            }
            else if(y>iYt || iB>iYt)
            {
                //1.3
                int x;
                x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
                if(iXl<=x && x<=iXr)//
                {
                    m_ptFrom.x=x;
                    m_ptFrom.y=iYt;
                }else return false;//否则无交点
            }
        }

    }else if(iA>iXr)
    {
        if(iC>iXr) return false;//
        else
        {
            int y;
            y=iB-((iA-iXr)*(iB-iD)/(iA-iC));
            
            if(iYb<=y && y<=iYt)
            {
                m_ptFrom.x=iXr;
                m_ptFrom.y=y;
            }else if ((y<iYb || y>iYt) && (iYb<=iB && iB<=iYt)) 
            {
                return false;
            }
            else if(y<iYb || iB<iYb)
            {
                //1.2
                int x;
                x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
                if(iXl<=x && x<=iXr)//检验x的有校性
                {
                    m_ptFrom.x=x;
                    m_ptFrom.y=iYb;
                }else return false;//否则无交点
            }
            else if(y>iYt || iB>iYt)
            {
                //1.3
                int x;
                x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
                if(iXl<=x && x<=iXr)//
                {
                    m_ptFrom.x=x;
                    m_ptFrom.y=iYt;
                }else return false;//否则无交点
            }

        }

    }
/**///////////////////////////////////////////////////////////////////////////////////

    if(iXl<=iC && iC<=iXr)
    {
        if(iYb<=iD && iD<=iYt) 
            return true;//m_ptFrom保持原值
        else if(iB<iYb && iD<iYb) return false;//与窗口无交.
        else if(iD<iYb && iB>=iYb)
        {
            //1.2
            int x;
            x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
            if(iXl<=x && x<=iXr)//检验x的有校性
            {
                m_ptTo.x=x;
                m_ptTo.y=iYb;
                return true;
            }else return false;//否则无交点
        }else if(iB>iYt && iD>iYt) return false;
        else if(iD>iYt && iB<=iYt)
        {    
            //1.3
            int x;
            x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
            if(iXl<=x && x<=iXr)//
            {
                m_ptTo.x=x;
                m_ptTo.y=iYt;
                return true;
            }else return false;//否则无交点

        }
        

    }else if(iC<iXl)
    {
        if(iA<iXl) return false;
        else
        {
            int y;
            y=iB-((iA-iXl)*(iB-iD)/(iA-iC));

            if(iYb<=y && y<=iYt)
            {
                m_ptTo.x=iXl;
                m_ptTo.y=y;
                return true;
            }else if ((y<iYb || y>iYt) && (iYb<=iD && iD<=iYt)) 
            {
                return false;
            }
            else if(y<iYb || iB<iYb)
            {
                //1.2
                int x;
                x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
                if(iXl<=x && x<=iXr)//检验x的有校性
                {
                    m_ptTo.x=x;
                    m_ptTo.y=iYb;
                    return true;
                }else return false;//否则无交点
            }
            else if(y>iYt || iB>iYt)
            {
                //1.3
                int x;
                x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
                if(iXl<=x && x<=iXr)//
                {
                    m_ptTo.x=x;
                    m_ptTo.y=iYt;
                    return true;
                }else return false;//否则无交点
            }
        }

    }else if(iC>iXr)
    {
        if(iA>iXr) return false;//
        else
        {
            int y;
            y=iB-((iA-iXr)*(iB-iD)/(iA-iC));
            
            if(iYb<=y && y<=iYt)
            {
                m_ptTo.x=iXr;
                m_ptTo.y=y;
                return true;
            }else if ((y<iYb || y>iYt) && (iYb<=iD && iD<=iYt)) 
            {
                return false;
            }
            else if(y<iYb || iD<iYb)
            {
                //1.2
                int x;
                x=iA-((iB-iYb)*(iA-iC)/(iB-iD));
                if(iXl<=x && x<=iXr)//检验x的有校性
                {
                    m_ptTo.x=x;
                    m_ptTo.y=iYb;
                    return true;
                }else return false;//否则无交点
            }
            else if(y>iYt || iB>iYt)
            {
                //1.3
                int x;
                x=iA-((iB-iYt)*(iA-iC)/(iB-iD));//检验x的有校性 
                if(iXl<=x && x<=iXr)//
                {
                    m_ptTo.x=x;
                    m_ptTo.y=iYt;
                    return true;
                }else return false;//否则无交点
            }

        }

    }
    return true;
    
}