C#计算旋转中心以及旋转后坐标算法

这个东西基本上每个做视觉项目的工程师都用到过，前几天看见群里有人在问，正好最近有空写了个demo，没有测试过，应该是没有问题的。旋转中心如何计算这个问题还搞不明白的，自己好好锻炼下二维平面想象能力。

C#计算旋转中心以及旋转后坐标算法

实现代码

首先定义坐标与圆的结构体，方便使用。

public struct Cicular {
public double X;
public double Y;
public double R;
}
public struct mPoint
{
public double X;
public double Y;
}

计算经过三点坐标的圆的方法

/// <summary>
/// 求经过三点的圆
/// </summary>
/// <param name="px1">坐标1</param>
/// <param name="px2">坐标2</param>
/// <param name="px3">坐标3</param>
/// <param name="C">结果圆</param>
public void CalculateCicular(mPoint px1, mPoint px2, mPoint px3, out Cicular C)
{

double x1, y1, x2, y2, x3, y3;
double a, b, c, g, e, f;
x1 = px1.X;
y1 = px1.Y;
x2 = px2.X;
y2 = px2.Y;
x3 = px3.X;
y3 = px3.Y;
e = 2 * (x2 - x1);
f = 2 * (y2 - y1);
g = x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1;
a = 2 * (x3 - x2);
b = 2 * (y3 - y2);
c = x3 * x3 - x2 * x2 + y3 * y3 - y2 * y2;
C.X = (g * b - c * f) / (e * b - a * f);
C.Y = (a * g - c * e) / (a * f - b * e);
C.R = Math.Sqrt((C.X - x1) * (C.X - x1) + (C.Y - y1) * (C.Y - y1));

}

计算坐标p1以坐标p2为中心旋转A角度后坐标p3

/// <summary>/// 计算坐标1以坐标2为中心旋转后坐标/// </summary>/// <param name="p1">坐标1</param>/// <param name="ARotate">旋转角度</param>/// <param name="p2">坐标2</param>/// <param name="p3">旋转后坐标</param>/// <returns>运行状态</returns>public string RotateAngle(mPoint p1, double ARotate, mPoint p2, out mPoint p3){try{double Rad = 0;Rad = ARotate * Math.Acos(-1) / 180;p3.X = (p2.X - p1.X) * Math.Cos(Rad) - (p2.Y - p1.Y) * Math.Sin(Rad) + p1.X;p3.Y = (p2.Y - p1.Y) * Math.Cos(Rad) + (p2.X - p1.X) * Math.Sin(Rad) + p1.Y;return "OK";}catch (Exception ex){p3.X=999999;p3.Y = 999999;return ex.Message;}}

简单使用

计算经过三点的圆

 private void button1_Click(object sender, EventArgs e)
{
Cicular C;
mPoint p1; 
mPoint p2;
mPoint p3;
p1.X =(double) point1_x.Value;
p1.Y = (double)point1_y.Value;
p2.X = (double)point2_x.Value;
p2.Y = (double)point2_y.Value;
p3.X = (double)point3_x.Value;
p3.Y = (double)point3_y.Value;
CalculateCicular(p1, p2, p3,out C);
X.Value =(decimal) C.X;
Y.Value = (decimal)C.Y;
R.Value = (decimal)C.R;
Console.WriteLine(C.X+"///"+C.Y+"///"+C.R);
}

坐标值自行赋值。

计算旋转后坐标

private void button2_Click(object sender, EventArgs e)
{
mPoint p1, p2, p3;
p1.X = (double)X.Value;
p1.Y = (double)Y.Value;
p2.X = (double)p_x.Value;
p2.Y = (double)p_y.Value;
//顺时针角度为负数
RotateAngle(p1,(double)A.Value,p2,out p3);
point_xz_x.Value = (decimal)p3.X;
point_xz_y.Value = (decimal)p3.Y;
Console.WriteLine(p3.X + ","+ p3.Y);
}

实现方式较为简单，主要是三角函数的应用。C#涉及到结构体以及out关键字的使用，关于out与ref的区别后续再讲。