pyclipper和ClipperLib操作多边型

1. 等距离缩放多边形

1.1 python

1.2 c++

1. 等距离缩放多边形

1.1 python

环境配置

pip install opencv-python opencv-contrib-python
pip install pyclipper
pip install numpy

import cv2
import numpy as np
import pyclipper


def equidistant_zoom_contour(contour, margin):
    """
    等"距离"缩放多边形轮廓点
    :param contour: 一个图形的轮廓格式[[[x1, x2]],...],shape是(-1, 1, 2)
    :param margin: 轮廓外扩的像素距离，margin正数是外扩，负数是缩小
    :return: 外扩后的轮廓点
    """
    pco = pyclipper.PyclipperOffset()
    #  参数限制，默认成2，这里设置大一些，主要是用于多边形的尖角是否用圆角代替
    pco.MiterLimit = 10  # 2是圆角，10是尖角
    contour = contour[:, 0, :]
    pco.AddPath(contour, pyclipper.JT_MITER, pyclipper.ET_CLOSEDPOLYGON)
    solution = pco.Execute(margin)
    solution = np.array(solution).reshape(-1, 1, 2).astype(int)
    return solution


if __name__ == '__main__':
    poly = np.array([[[200, 200]], [[200, 300]], [[400, 350]], [[350, 200]], [[300, 200]], [[200, 100]]])
    contour1 = equidistant_zoom_contour(poly, 20)  # 等距离
    img = np.zeros((500, 500, 3))
    cv2.polylines(img, [contour1], True, (0, 255, 0), 3)
    cv2.polylines(img, [poly], True, (0, 0, 255), 3)

    cv2.namedWindow("img", cv2.WINDOW_NORMAL), cv2.imshow("img", img), cv2.waitKey()

参数MiterLimit=10是尖角（左图），默认值是2，圆角（右图）

1.2 c++

第一版clipper: Download Clipper

最新版clipper2: https://github.com/AngusJohnson/Clipper2

官方介绍：https://angusj.com/clipper2/Docs/Overview.htm

（1）这里使用旧版clipper，下载后解压

（2）vs2019配置clipper环境，只需要添加包含目录即可。

（3）添加现有clipper头文件和源码 clipper.cpp和clipper.hpp

#include <iostream>
#include <vector>
#include <clipper.hpp>

using namespace ClipperLib;

std::vector<IntPoint> equidistant_zoom_contour(const std::vector<std::vector<IntPoint>>& contours, double margin) {
    ClipperOffset co;
    co.MiterLimit = 10;  // 默认2圆角，10尖角
    co.AddPaths(contours, jtMiter, etClosedPolygon);
    Paths solution;
    co.Execute(solution, margin);

    std::vector<IntPoint> result;
    for (const auto& path : solution) {
        result.insert(result.end(), path.begin(), path.end());
    }

    return result;
}

int main() {
    Paths poly = {
        {{200, 200}, {200, 300}, {400, 350}, {350, 200}, {300, 200}, {200, 100}}
    };

    double margin = 20.0;

    std::vector<IntPoint> contour1 = equidistant_zoom_contour(poly, margin);

    cv::Mat img = cv::Mat::zeros(500, 500, CV_8UC3);
    std::vector<std::vector<cv::Point>> contours_cv(1);
    for (const auto& point : contour1) {
        contours_cv[0].emplace_back(point.X, point.Y);
    }

    cv::polylines(img, contours_cv, true, cv::Scalar(0, 255, 0), 3);

    contours_cv.clear();
    for (const auto& path : poly) {
        std::vector<cv::Point> contour_cv;
        for (const auto& point : path) {
            contour_cv.emplace_back(point.X, point.Y);
        }
        contours_cv.push_back(contour_cv);
    }

    cv::polylines(img, contours_cv, true, cv::Scalar(0, 0, 255), 3);

    cv::namedWindow("img", cv::WINDOW_NORMAL);
    cv::imshow("img", img);
    cv::waitKey(0);

    return 0;
}

MiterLimit默认2圆角（左图），10尖角（右图）