多边形扩展算法

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多边形扩展算法[code]c++语言。



//Point2D 的类定义，也包括运算符重构

class Point2D  {

public:
float x;
float y;

    Point2D()
{
  x=0;y=0;
}

Point2D(float x, float y)
{
  this->x=x;this->y=y;
}

friend Point2D operator +(Point2D a, Point2D b)
{
  Point2D p;
  p.x=a.x+b.x;
  p.y=a.y+b.y;
  return p;
};

friend Point2D operator -(Point2D a, Point2D b)
{
  Point2D p;
  p.x=a.x-b.x;
  p.y=a.y-b.y;
  return p;
};

friend float operator *(Point2D a, Point2D b)
{
  float p=a.x*b.x+a.y*b.y;
  return p;
};

friend Point2D operator *(Point2D a, float value)
{
  Point2D p;
  p.x=a.x*value;
  p.y=a.y*value;
  return p;
};

friend float xlJi(Point2D a, Point2D b)
{
  float p=((a.x)*(b.y))-((a.y)*(b.x));
  return p;
};

};


//测试程序

int main()

{
std::vector<Point2D> pList;
std::vector<Point2D> DpList;
std::vector<Point2D> nDpList;
std::vector<Point2D> newList;

Point2D  p2d,p2;
//p2d.x=0;p2d.y=0;pList.push_back(p2d);
//p2d.x=0;p2d.y=100;pList.push_back(p2d);
//p2d.x=100;p2d.y=100;pList.push_back(p2d);
//p2d.x=50;p2d.y=50;pList.push_back(p2d);
//p2d.x=100;p2d.y=0;pList.push_back(p2d);
//--注释的是原文数据，我这里把数据的顺序反了一下
p2d.x=0;p2d.y=0;pList.push_back(p2d);
p2d.x=100;p2d.y=0;pList.push_back(p2d);
p2d.x=50;p2d.y=50;pList.push_back(p2d);
p2d.x=100;p2d.y=100;pList.push_back(p2d);
p2d.x=0;p2d.y=100;pList.push_back(p2d);



//-------------------------------------------

int i,index,count;
count=pList.size();
for(i=0;i<count;i++)
{
  index=(i+1)%count;
  p2d=pList[index]-pList[i];
  DpList.push_back(p2d);
}
// 初始化ndpList，单位化两顶点向量差
float r;
for(i=0;i<count;i++)
{
  r=sqrt(DpList[i]*DpList[i]);
  r=1/r;
  p2d=DpList[i]*r;
  nDpList.push_back(p2d);
}


// 计算新顶点， 注意参数dist为负是向内收缩， 为正是向外扩张
//上述说法只是对于顺时针而言
//我把数据改为逆时针，结论刚好相反
float lenth;
float dist=5;
int startindex,endindex;
for(i=0;i<count;i++)
{
  startindex= i==0?count-1:i-1;
  endindex=i;
  float sina=xlJi(nDpList[startindex],nDpList[endindex]);
  lenth=dist/sina;
  p2d=nDpList[endindex]-nDpList[startindex];
  p2=pList[i]+p2d*lenth;
  newList.push_back(p2);
  TRACE(" %.1f,%.1f\n",p2.x,p2.y);
}

return 0;
}

原文链接：https://blog.csdn.net/leon_zeng0/article/details/73500174[/code]