如何使用.Net绘制多边形并计算其面积 [英] how to draw polygon and calculate its area using .Net

问题描述

如何使用鼠标绘制多边形然后使用asp.net计算其面积。

解决方案

好的，这实际上并不困难，但你需要想一想，做几件事。



如果我假设你在面板上画画，那么你需要设置一个Point对象列表：

  private 列表< Point> polygon =  null ; 
 

这将在你创建它时保存多边形顶点。

然后你需要处理Panel.MouseClick事件：

< pre lang =c＃> private void myPolygonPanel_MouseClick（ object sender，MouseEventArgs e）
{
if （polygon == null ）
{
polygon = new List< Point>（）;
}
polygon.Add（e.Location）;
myPolygonPanel.Invalidate（）;
}

以及Paint事件：

  private   void  myPolygonPanel_Paint（ object  sender，PaintEventArgs e）
 {
  if （polygon！=  null && polygon.Count > ;   1 ）
 {
  for （ int  i =  0 ; i <  polygon.Count  -  1 ; i ++）
 {
 e.Graphics.DrawLine（Pens.Red，polygon [i]，polygon [i +  1 ]）; 
} 
} 
} 
 

计算面积是另一回事：这是一个简单的Brute-Force-Ignorance方法，由C ++转换而来/>

  double  GetArea（List< Point> polygon）
 {
  double  area =  0 。 0 ; 
  for （ int  i =  0 ; i <  polygon.Count; i ++）
 {
  int  j =（i +  1 ）％polygon.Count; 
 area + = polygon [i] .X * polygon [j] .Y; 
 area  -  = polygon [i] .Y * polygon [j] .X; 
} 
 area / =  2 ; 
  if （area <   0 ）
 {
 area = -area; 
} 
 返回区域; 
} 
 

你可能想要更聪明一点！ Wiki可能对您有所帮助。

How to draw a polygon using mouse then after calculate its area using asp.net.

解决方案

Ok, this isn''t actually difficult, but you need to think about it, and do a few things.

If I assume you draw on a panel, then you need to set up a list of Point objects:

private List<Point> polygon = null;

This will hold the polygon vertices as you create it.
You then need to handle the Panel.MouseClick event:

private void myPolygonPanel_MouseClick(object sender, MouseEventArgs e)
    {
    if (polygon == null)
        {
        polygon = new List<Point>();
        }
    polygon.Add(e.Location);
    myPolygonPanel.Invalidate();
    }

And the Paint event:

private void myPolygonPanel_Paint(object sender, PaintEventArgs e)
    {
    if (polygon != null && polygon.Count > 1)
        {
        for (int i = 0; i < polygon.Count - 1; i++)
            {
            e.Graphics.DrawLine(Pens.Red, polygon[i], polygon[i + 1]);
            }
        }
    }

Calculating the area is another matter: this is a simple Brute-Force-and-Ignorance method converted from C++

double GetArea(List<Point> polygon)
    {
    double area = 0.0;
    for (int i = 0; i < polygon.Count; i++)
        {
        int j = (i + 1) % polygon.Count;
        area += polygon[i].X * polygon[j].Y;
        area -= polygon[i].Y * polygon[j].X;
        }
    area /= 2;
    if (area < 0)
        {
        area = -area;
        }
    return area;
    }

You may want to be a little more intelligent! Wiki can probably help you.

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