30 OpenCV 点多边形测试

点多边形测试

pointPolygonTest

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
)

返回数据是double类型

示例

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace std;
using namespace cv;

int main(int argc, char** argv) {
    // 创建一个空白的图像
    const int r = 100;
    Mat src = Mat::zeros(r * 4, r * 4, CV_8UC1);

    // 定义六边形的顶点
    vector<Point2f> vert(6);
    vert[0] = Point(3 * r / 2, static_cast<int>(1.34*r));   
    vert[1] = Point(1 * r, 2 * r);
    vert[2] = Point(3 * r / 2, static_cast<int>(2.866*r));   
    vert[3] = Point(5 * r / 2, static_cast<int>(2.866*r));
    vert[4] = Point(3 * r, 2 * r);   
    vert[5] = Point(5 * r / 2, static_cast<int>(1.34*r));

    // 在图像上绘制六边形
    for (int i = 0; i < 6; i++) {
        line(src, vert[i], vert[(i + 1) % 6], Scalar(255), 3, 8, 0);
    }

    // 查找轮廓
    vector<vector<Point>> contours;
    vector<Vec4i> hierachy;
    Mat csrc;
    src.copyTo(csrc);
    findContours(csrc, contours, hierachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));

    // 计算每个像素点到轮廓的距离
    Mat raw_dist = Mat::zeros(csrc.size(), CV_32FC1);
    for (int row = 0; row < raw_dist.rows; row++) {
        for (int col = 0; col < raw_dist.cols; col++) {
            // 计算当前像素到轮廓的距离
            double dist = pointPolygonTest(contours[0], Point2f(static_cast<float>(col), static_cast<float>(row)), true);
            // 将距离值转换为float类型并存储到raw_dist图像中
            raw_dist.at<float>(row, col) = static_cast<float>(dist);
        }
    }

    // 将距离映射到颜色，并创建一个新的图像
    double minValue, maxValue;
    minMaxLoc(raw_dist, &minValue, &maxValue, 0, 0, Mat());
    Mat drawImg = Mat::zeros(src.size(), CV_8UC3);
    for (int row = 0; row < drawImg.rows; row++) {
        for (int col = 0; col < drawImg.cols; col++) {
            float dist = raw_dist.at<float>(row, col);
            if (dist > 0) {
                // 正距离映射到蓝色通道
                drawImg.at<Vec3b>(row, col)[0] = (uchar)(abs(1.0 - (dist / maxValue)) * 255);
            }
            else if (dist < 0) {
                // 负距离映射到红色通道
                drawImg.at<Vec3b>(row, col)[2] = (uchar)(abs(1.0 - (dist / minValue)) * 255);
            } else {
                // 距离为0的像素点设为白色
                drawImg.at<Vec3b>(row, col)[0] = (uchar)(abs(255 - dist));
                drawImg.at<Vec3b>(row, col)[1] = (uchar)(abs(255 - dist));
                drawImg.at<Vec3b>(row, col)[2] = (uchar)(abs(255 - dist));
            }
        }
    }

    // 创建窗口并显示图像
    const char* output_win = "point polygon test demo";
    char input_win[] = "input image";
    namedWindow(input_win, CV_WINDOW_AUTOSIZE);
    namedWindow(output_win, CV_WINDOW_AUTOSIZE);

    imshow(input_win, src);
    imshow(output_win, drawImg);

    waitKey(0);
    return 0;
}