C++ 使用pcl 把pcd点云文件保存为图片，只有intensity的值

可以使用PCL自带的可视化库来实现将pcd点云文件保存为图片，只保存intensity的值。具体步骤如下：

1. 加载pcd文件：

pcl::PointCloud<pcl::PointXYZI>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZI>);
pcl::io::loadPCDFile("input.pcd", *cloud);

2. 创建可视化对象和渲染器：

pcl::visualization::PCLVisualizer viewer("Cloud Viewer");
viewer.addPointCloud(cloud);
viewer.setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 1, "cloud");
viewer.setBackgroundColor(1, 1, 1);

3. 定义颜色映射表：

pcl::visualization::LookupTable lut;
lut.insert(std::make_pair(0.0, cv::Vec3b(0, 0, 0)));
lut.insert(std::make_pair(1.0, cv::Vec3b(255, 255, 255)));

4. 将intensity的值转换为0到1之间的浮点数，并映射到颜色映射表上：

cv::Mat intensity_image(cloud->height, cloud->width, CV_8UC3);
for (int y = 0; y < intensity_image.rows; y++) {
    for (int x = 0; x < intensity_image.cols; x++) {
        float intensity = cloud->at(x, y).intensity;
        cv::Vec3b color = lut.getColor(intensity);
        intensity_image.at<cv::Vec3b>(y, x) = color;
    }
}

5. 保存图片：

cv::imwrite("output.png", intensity_image);

完整代码如下：

#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
#include <pcl/visualization/pcl_visualizer.h>
#include <opencv2/opencv.hpp>

int main(int argc, char** argv) {
    pcl::PointCloud<pcl::PointXYZI>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZI>);
    pcl::io::loadPCDFile("input.pcd", *cloud);

    pcl::visualization::PCLVisualizer viewer("Cloud Viewer");
    viewer.addPointCloud(cloud);
    viewer.setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 1, "cloud");
    viewer.setBackgroundColor(1, 1, 1);

    pcl::visualization::LookupTable lut;
    lut.insert(std::make_pair(0.0, cv::Vec3b(0, 0, 0)));
    lut.insert(std::make_pair(1.0, cv::Vec3b(255, 255, 255)));

    cv::Mat intensity_image(cloud->height, cloud->width, CV_8UC3);
    for (int y = 0; y < intensity_image.rows; y++) {
        for (int x = 0; x < intensity_image.cols; x++) {
            float intensity = cloud->at(x, y).intensity;
            cv::Vec3b color = lut.getColor(intensity);
            intensity_image.at<cv::Vec3b>(y, x) = color;
        }
    }

    cv::imwrite("output.png", intensity_image);

    return 0;
}