C++使用opencv判断一个点是否在多边形之内

#include <opencv2/opencv.hpp>
CvMat* g_pMatContour = NULL;
static void process(...)
{
    if (g_pMatContour == NULL)
    {
        float points[] ={470,240, 1670,168, 1846,688, 714,928};
        int nContourNum = 4;
        g_pMatContour = cvCreateMat(1, nContourNum, CV_32FC2);
        for (int i=0; i<nContourNum; i++)
        {
            CvScalar vertex = cvScalar(points[i*2], points[i*2+1]);
            cvSet1D(pMatContour, i, vertex);
        }
    }
    CvPoint2D32f ptTest;
    //center point
    ptTest.x = pClip->left + pClip->width /2;
    ptTest.y = pClip->top  + pClip->height/2;
    double jl = cvPointPolygonTest(g_pMatContour, ptTest, 1);
    //jl > 0表示在内部。jl<0表示在外部。jl=0表示在多边形上。
    if (jl > 0)
    {
        //WARNING MESSAGE
    }