opencv::点多边形测试

点多边形测试
    测试一个点是否在给定的多边形内部，边缘或者外部

double pointPolygonTest(
    InputArray  contour,    // 输入的轮廓
    Point2f  pt,             // 测试点
    bool  measureDist         // 是否返回距离值，如果是false，1表示在内面，0表示在边界上，-1表示在外部，true返回实际距离
)

步骤
    构建一张400x400大小的图片， Mat::Zero(, , CV_8UC1)
    画上一个六边形的闭合区域line
    发现轮廓
    对图像中所有像素点做点 多边形测试，得到距离，归一化后显示。

int main(int argc, char** argv) {
    const int r = ;
    Mat src = Mat::zeros(r * , r * , CV_8UC1);

    vector<Point2f> vert();
    vert[] = Point( * r / , static_cast<int>(1.34*r));
    vert[] = Point( * r,  * r);
    vert[] = Point( * r / , static_cast<int>(2.866*r));
    vert[] = Point( * r / , static_cast<int>(2.866*r));
    vert[] = Point( * r,  * r);
    vert[] = Point( * r / , static_cast<int>(1.34*r));

    for (int i = ; i < ; i++) {
        line(src, vert[i], vert[(i + ) % ], Scalar(), , , );
    }
    // 画一个六边型
    imshow("input_win", src);

    vector<vector<Point>> contours;
    vector<Vec4i> hierachy;
    Mat csrc;
    src.copyTo(csrc);
    //边界发现
    findContours(csrc, contours, hierachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(, ));
    Mat raw_dist = Mat::zeros(csrc.size(), CV_32FC1);
    for (int row = ; row < raw_dist.rows; row++) {
        for (int col = ; col < raw_dist.cols; col++) {
            double dist = pointPolygonTest(contours[], Point2f(static_cast<float>(col), static_cast<float>(row)), true);
            raw_dist.at<float>(row, col) = static_cast<float>(dist);
        }
    }

    double minValue, maxValue;
    minMaxLoc(raw_dist, &minValue, &maxValue, , , Mat());
    Mat drawImg = Mat::zeros(src.size(), CV_8UC3);
    for (int row = ; row < drawImg.rows; row++) {
        for (int col = ; col < drawImg.cols; col++) {
            float dist = raw_dist.at<float>(row, col);
            if (dist > ) {
                //内部
                drawImg.at<Vec3b>(row, col)[] = (uchar)(abs(1.0 - (dist / maxValue)) * );
            }
            else if (dist < ) {
                //外部
                drawImg.at<Vec3b>(row, col)[] = (uchar)(abs(1.0 - (dist / minValue)) * );
            }
            else {
                //边缘
                drawImg.at<Vec3b>(row, col)[] = (uchar)(abs( - dist));
                drawImg.at<Vec3b>(row, col)[] = (uchar)(abs( - dist));
                drawImg.at<Vec3b>(row, col)[] = (uchar)(abs( - dist));
            }
        }
    }

    imshow("output_win", drawImg);

    waitKey();
    return ;
}