帮我写一段c++代码，输入pcd点云文件，利用cgal中的alphashape函数检测点云边缘并保存

好的，以下是一个基本的C++代码，可以读取PCD文件，使用CGAL库中的AlphaShape函数检测点云的边缘，并将结果保存为OFF文件：

#include <iostream>
#include <fstream>
#include <vector>

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Alpha_shape_3.h>
#include <CGAL/IO/read_ply_points.h>
#include <CGAL/IO/write_off_points.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Alpha_shape_vertex_base_3<K> Vb;
typedef CGAL::Alpha_shape_cell_base_3<K> Fb;
typedef CGAL::Triangulation_data_structure_3<Vb, Fb> Tds;
typedef CGAL::Alpha_shape_3<K, Tds> Alpha_shape_3;
typedef K::Point_3 Point_3;

int main(int argc, char** argv) {
    if (argc < 3) {
        std::cerr << "Usage: " << argv[0] << " input.pcd output.off" << std::endl;
        return 1;
    }

    // load PCD file
    std::vector<Point_3> points;
    if (!CGAL::read_ply_points(std::ifstream(argv[1]), std::back_inserter(points))) {
        std::cerr << "Failed to read PCD file." << std::endl;
        return 1;
    }

    // compute alpha shape
    Alpha_shape_3 alpha_shape(points.begin(), points.end(), 0.0);
    alpha_shape.set_alpha(1.0);

    // write alpha shape as OFF file
    std::ofstream ofs(argv[2]);
    if (!ofs) {
        std::cerr << "Failed to open output file." << std::endl;
        return 1;
    }
    CGAL::write_off_points(ofs, alpha_shape.alpha_shape_vertices_begin(), alpha_shape.alpha_shape_vertices_end());
    return 0;
}

请注意，这只是一个基本的示例代码，可能需要根据你的具体需求进行修改。此外，你需要确保已正确安装CGAL库，并正确链接库文件。