用c++判断轮廓与直线是否相交

可以使用 OpenCV 库中的函数 cv::intersectConvexConvex() 来判断轮廓与直线是否相交。该函数可以判断两个凸多边形是否相交，因此需要将直线转换为一个长度为无穷大的矩形，然后将轮廓转换为一个凸多边形，最后调用该函数即可。具体实现可以参考以下代码：

#include <opencv2/opencv.hpp>

using namespace cv;

bool isIntersect(const std::vector<Point>& contour, const Vec4i& line)
{
    // Convert line to a rectangle with infinite length
    Rect rect(0, 0, INT_MAX, INT_MAX);
    lineToRect(line, rect);

    // Convert contour to a convex polygon
    std::vector<Point> convexContour;
    convexHull(contour, convexContour);

    // Check if the convex polygon and the rectangle intersect
    std::vector<Point2f> intersection;
    bool isIntersect = intersectConvexConvex(convexContour, rect, intersection);

    return isIntersect;
}

void lineToRect(const Vec4i& line, Rect& rect)
{
    int x1 = line[0], y1 = line[1], x2 = line[2], y2 = line[3];
    if (x1 == x2) {
        rect.x = x1;
        rect.y = 0;
        rect.width = 1;
        rect.height = INT_MAX;
    } else if (y1 == y2) {
        rect.x = 0;
        rect.y = y1;
        rect.width = INT_MAX;
        rect.height = 1;
    } else {
        float k = (float)(y2 - y1) / (float)(x2 - x1);
        float b = y1 - k * x1;
        if (k > 0) {
            rect.x = 0;
            rect.y = b;
            rect.width = INT_MAX;
            rect.height = k * INT_MAX;
        } else {
            rect.x = INT_MAX;
            rect.y = k * INT_MAX + b;
            rect.width = INT_MAX;
            rect.height = -k * INT_MAX;
        }
    }
}

其中，lineToRect() 函数将直线转换为一个矩形，isIntersect() 函数判断轮廓与直线是否相交。