1. 基于pcl 和 liblas 库 las与pcd格式（rgb点）相互转换（win10 VS2013 X64环境 ）

#include <liblas/liblas.hpp>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <cmath>
#include <pcl/point_cloud.h>
#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
#include <pcl/visualization/pcl_visualizer.h>

//  实现Unshort转为Unchar类型
//int Unshort2Unchar(uint16_t &green, uint8_t &g)
//{
//    unsigned short * word;
//    word = &green;
//    int size = WideCharToMultiByte(CP_ACP, 0, LPCWSTR(word), -1, NULL, 0, NULL, FALSE);
//    char *AsciiBuff=new char[size];
//    WideCharToMultiByte(CP_ACP, 0, LPCWSTR(word), -1, AsciiBuff, size, NULL, FALSE);
//    g = *AsciiBuff;
//
//    delete[] AsciiBuff;
//    AsciiBuff = NULL;
//    return 0;
//}

void writePointCloudFromLas(const char* strInputLasName, const char* strOutPutPointCloudName)
{
    //打开las文件
    std::ifstream ifs;
    ifs.open(strInputLasName, std::ios::in | std::ios::binary);
    if (!ifs.is_open())
    {
        std::cout << "无法打开.las" << std::endl;
        return;
    }
    liblas::ReaderFactory readerFactory;
    liblas::Reader reader = readerFactory.CreateWithStream(ifs);
    //写点云
    pcl::PointCloud<pcl::PointXYZRGBA>::Ptr cloudOutput(new pcl::PointCloud<pcl::PointXYZRGBA>());
    cloudOutput->clear();
    while (reader.ReadNextPoint())
    {
        double x = reader.GetPoint().GetX();
        double y = reader.GetPoint().GetY();
        double z = reader.GetPoint().GetZ();
        uint16_t red = reader.GetPoint().GetColor()[0];
        uint16_t green = reader.GetPoint().GetColor()[1];
        uint16_t blue = reader.GetPoint().GetColor()[2];
        
        /*****颜色说明
        *   uint16_t  范围为0-256*256 ；
        *   pcl 中 R  G  B利用的unsigned char  0-256；  
        *   因此这里将uint16_t 除以256  得到  三位数的0-256的值  
        *   从而进行rgba 值32位 的位运算。
        *
        ******/

        pcl::PointXYZRGBA thePt;  //int rgba = 255<<24 | ((int)r) << 16 | ((int)g) << 8 | ((int)b);
        thePt.x = x; thePt.y = y; thePt.z = z; 
        thePt.rgba = (uint32_t)255 << 24 | (uint32_t)(red / 256) << 16 | (uint32_t)(green / 256) << 8 | (uint32_t)(blue / 256);
            //uint32_t rgb = *reinterpret_cast<int*>(&thePt.rgb);  //reinterpret_cast 强制转换
        cloudOutput->push_back(thePt);
    }

    //boost::shared_ptr<pcl::visualization::PCLVisualizer> viewer(new pcl::visualization::PCLVisualizer("3D Viewer"));
    //viewer->setBackgroundColor(0, 0, 0); //设置背景
    //viewer->addPointCloud(cloudOutput,"cloudssd");
    //while (!viewer->wasStopped()){
    //    viewer->spinOnce();
    //}
    pcl::io::savePCDFileASCII(strOutPutPointCloudName, *cloudOutput);
    cloudOutput->clear();
}

//读入点云，写.las

void writeLasFromPointCloud3(const char* strInputPointCloudName, const char* strOutLasName)
{
    std::ofstream ofs(strOutLasName, ios::out | ios::binary);
    if (!ofs.is_open())
    {
        std::cout << "err  to  open  file  las....." << std::endl;
        return;
    }
    liblas::Header header;
    header.SetVersionMajor(1);
    header.SetVersionMinor(2);
    header.SetDataFormatId(liblas::PointFormatName::ePointFormat3);
    header.SetScale(0.001, 0.001, 0.001);

    pcl::PointCloud<pcl::PointXYZRGBA>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZRGBA>);
    pcl::io::loadPCDFile(strInputPointCloudName, *cloud);
    std::cout << "总数:" << cloud->points.size() << std::endl;
    //写liblas,
    liblas::Writer writer(ofs, header);
    liblas::Point point(&header);

    for (size_t i = 0; i < cloud->points.size(); i++)
    {
        double x = cloud->points[i].x;
        double y = cloud->points[i].y;
        double z = cloud->points[i].z;
        point.SetCoordinates(x, y, z);

        uint32_t red = (uint32_t)cloud->points[i].r;
        uint32_t green = (uint32_t)cloud->points[i].g;
        uint32_t blue = (uint32_t)cloud->points[i].b;
        liblas::Color pointColor(red, green, blue);
        point.SetColor(pointColor);
        writer.WritePoint(point);
        //std::cout << x << "," << y << "," << z << std::endl;
    }
    double minPt[3] = { 9999999, 9999999, 9999999 };
    double maxPt[3] = { 0, 0, 0 };
    header.SetPointRecordsCount(cloud->points.size());
    header.SetPointRecordsByReturnCount(0, cloud->points.size());
    header.SetMax(maxPt[0], maxPt[1], maxPt[2]);
    header.SetMin(minPt[0], minPt[1], minPt[2]);
    writer.SetHeader(header);
}

int main()
{
    //char strInputLasName[] = "qq.las";//"Scan_az001.las";
    //char strOutPutPointCloudName[]="qqqq.pcd";
    //writePointCloudFromLas(strInputLasName, strOutPutPointCloudName);

    //std::string strInputPointCloudName = "eewge";
    //std::string strOutLasName = "eewge";
    //writeLasFromPointCloud(strInputPointCloudName.c_str(), strOutLasName.c_str());
    char strInputPointCloudName[] = "qq.pcd";
    char strOutLasName[] = "qq.las";
    writeLasFromPointCloud3(strInputPointCloudName, strOutLasName);

    return 0;
}