线段余弦角+凸包算法

///
/// 根据余弦定理求两个线段夹角
///
/// 端点
/// start点
/// end点
///
double Angle(PointF o, PointF s, PointF e)
{
double cosfi = 0, fi = 0, norm = 0;
double dsx = s.X - o.X;
double dsy = s.Y - o.Y;
double dex = e.X - o.X;
double dey = e.Y - o.Y;
cosfi = dsx * dex + dsy * dey;
norm = (dsx * dsx + dsy * dsy) * (dex * dex + dey * dey);
cosfi /= Math.Sqrt(norm);
if (cosfi >= 1.0) return 0;
if (cosfi <= -1.0) return Math.PI;
fi = Math.Acos(cosfi);
if (180 * fi / Math.PI < 180)
{
return 180 * fi / Math.PI;
}
else
{
return 360 - 180 * fi / Math.PI;
}
}

/// <summary>
/// 凸包算法
/// </summary>
/// <param name="_list"></param>
/// <returns></returns>
private List<TuLine> BruteForceTu(List<Info> _list)
{

//记录极点对
List<TuLine> role = new List<TuLine>();

//遍历
for (int i = 0; i < _list.Count - 1; i++)
{

for (int j = i + 1; j < _list.Count; j++)
{

double a = _list[j].Y - _list[i].Y;
double b = _list[i].X - _list[j].X;
double c = _list[i].X * _list[j].Y - _list[i].Y * _list[j].X;

int count = 0;
//将所有点代入方程
for (int k = 0; k < _list.Count; k++)
{

double result = a * _list[k].X + b * _list[k].Y - c;
if (result > 0)
{

count++;

}
else if (result < 0)
{

count--;

}

}
//是极点，则将连线记录下来
if (Math.Abs(count) == _list.Count - 2)
{

TuLine line = new TuLine();
IPoint pi = new PointClass();
pi.X = _list[i].X;
pi.Y = _list[i].Y;
line.Begin = pi;

IPoint Pj = new PointClass();
Pj.X = _list[j].X;
Pj.Y = _list[j].Y;
line.End = Pj;
role.Add(line);
}

}

}
return role;
}