判断一个点是否在一个复杂多边形的内部代码,C#代码库,德仔网

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【C#】判断一个点是否在一个复杂多边形的内部

作者:涌 / 发布于2017/9/11/ 795

判断一点是否在不规则图像的内部算法，如下图是由一个个点组成的不规则图像，判断某一点是否在不规则矩形内部

public class PositionAlgorithmHelper  
{  
    /// <summary>  
    /// 判断当前位置是否在不规则形状里面  
    /// </summary>  
    /// <param name="nvert">不规则形状的定点数</param>  
    /// <param name="vertx">当前x坐标</param>  
    /// <param name="verty">当前y坐标</param>  
    /// <param name="testx">不规则形状x坐标集合</param>  
    /// <param name="testy">不规则形状y坐标集合</param>  
    /// <returns></returns>  
    public static bool PositionPnpoly(int nvert, List<double> vertx, List<double> verty, double testx, double testy)  
    {  
        int i, j, c = 0;  
        for (i = 0, j = nvert - 1; i < nvert; j = i++)  
        {  
            if (((verty[i] > testy) != (verty[j] > testy)) && (testx < (vertx[j] - vertx[i]) * (testy - verty[i]) / (verty[j] - verty[i]) + vertx[i]))  
            {  
                c = 1 + c; ;  
            }  
        }  
        if (c % 2 == 0)  
        {  
            return false;  
        }  
        else  
        {  
            return true;  
        }  
    }  
}  


用上图坐标进行测试：
class Program  
{  
    static void Main(string[] args)  
    {  
        test1();  
    }  
  
    /// <summary>  
    /// test1  
    /// </summary>  
    public static void test1()  
    {  
        //不规则图像坐标  
        List<Position> position = new List<Position>();  
        position.Add(new Position() { x = 6, y = 0 });  
        position.Add(new Position() { x = 10, y = 2 });  
        position.Add(new Position() { x = 16, y = 2 });  
        position.Add(new Position() { x = 20, y = 6 });  
        position.Add(new Position() { x = 14, y = 10 });  
        position.Add(new Position() { x = 16, y = 6 });  
        position.Add(new Position() { x = 12, y = 6 });  
        position.Add(new Position() { x = 14, y = 8 });  
        position.Add(new Position() { x = 10, y = 8 });  
        position.Add(new Position() { x = 8, y = 6 });  
        position.Add(new Position() { x = 12, y = 4 });  
        position.Add(new Position() { x = 6, y = 4 });  
        position.Add(new Position() { x = 8, y = 2 });  
  
        //用户当前位置坐标  
        List<Position> userPositions = new List<Position>();  
        userPositions.Add(new Position() { x = 14, y = 4 });  
        userPositions.Add(new Position() { x = 15, y = 4 });  
        userPositions.Add(new Position() { x = 10, y = 6 });  
        userPositions.Add(new Position() { x = 8, y = 5 });  
  
        //不规则图像x坐标集合  
        List<double> xList = position.Select(x => x.x).ToList();  
        //不规则图像y坐标集合  
        List<double> yList = position.Select(x => x.y).ToList();  
  
        foreach (var userPosition in userPositions)  
        {  
            bool result = PositionAlgorithmHelper.PositionPnpoly(position.Count, xList, yList, userPosition.x, userPosition.y);  
  
            if (result)  
            {  
                Console.WriteLine(string.Format("{0},{1}【在】坐标内", userPosition.x, userPosition.y));  
            }  
            else  
            {  
                Console.WriteLine(string.Format("{0},{1}【不在】坐标内", userPosition.x, userPosition.y));  
            }  
        }  
    }  
}

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