使用PCL的PCL的fromROSMsg()函数将ROS的sensor_msgs::PointCloud2类型数据转换为PCL的pcl::PointCloud<T>类型数据时,假如T只是PointXYZ没问题,假如是PointXYZI,intensity这个field的数据类型是float,但是数据长度就是不对的,数据占8个字节而不是float的4个字节!toROSMsg()将PCL的pcl::PointCloud<T>类型数据转换为ROS的sensor_msgs::PointCloud2类型数据时则对数据类型和长度不作检查,完全照搬PCL里的PointXYZI的数据类型和长度,intensity占8个字节这样的有问题数据,rviz可以正常解释和播放展示,自己开发的软件在读取pcl库调用toROSMsg()转换生成的bag时通常根据intensity是float类型而认为数据长度是4个字节而读取到不正常的intensity数据而不能正常播放展示,这时需要自己实现类似fromROSMsg()和toROSMsg()这样的功能函数。
翻看了一下PCL相关源码,里面fromROSMsg()和toROSMsg()函数相关的代码如下:
/opt/ros/melodic/include/pcl_conversions/pcl_conversions.hnamespace pcl {
...
template<typename T>void toROSMsg(const pcl::PointCloud<T> &pcl_cloud, sensor_msgs::PointCloud2 &cloud){pcl::PCLPointCloud2 pcl_pc2;pcl::toPCLPointCloud2(pcl_cloud, pcl_pc2);pcl_conversions::moveFromPCL(pcl_pc2, cloud);}template<typename T>void fromROSMsg(const sensor_msgs::PointCloud2 &cloud, pcl::PointCloud<T> &pcl_cloud){pcl::PCLPointCloud2 pcl_pc2;pcl_conversions::toPCL(cloud, pcl_pc2);pcl::fromPCLPointCloud2(pcl_pc2, pcl_cloud);}...
}namespace pcl_conversions {...inlinevoid fromPCL(const pcl::PCLPointField &pcl_pf, sensor_msgs::PointField &pf){pf.name = pcl_pf.name;pf.offset = pcl_pf.offset;pf.datatype = pcl_pf.datatype;pf.count = pcl_pf.count;}inlinevoid fromPCL(const std::vector<pcl::PCLPointField> &pcl_pfs, std::vector<sensor_msgs::PointField> &pfs){pfs.resize(pcl_pfs.size());std::vector<pcl::PCLPointField>::const_iterator it = pcl_pfs.begin();int i = 0;for(; it != pcl_pfs.end(); ++it, ++i) {fromPCL(*(it), pfs[i]);}}inlinevoid copyPCLPointCloud2MetaData(const pcl::PCLPointCloud2 &pcl_pc2, sensor_msgs::PointCloud2 &pc2){fromPCL(pcl_pc2.header, pc2.header);pc2.height = pcl_pc2.height;pc2.width = pcl_pc2.width;fromPCL(pcl_pc2.fields, pc2.fields);//printf("pc2.fields.size() %d, ", pc2.fields.size());//printf("pcl_pc2.fields/pc2.fields: offset %d/%d, datatype %d/%d\n", pcl_pc2.fields[3].offset, pc2.fields[3].offset, pcl_pc2.fields[3].datatype, pc2.fields[3].datatype);pc2.is_bigendian = pcl_pc2.is_bigendian;pc2.point_step = pcl_pc2.point_step;pc2.row_step = pcl_pc2.row_step;pc2.is_dense = pcl_pc2.is_dense;}inlinevoid moveFromPCL(pcl::PCLPointCloud2 &pcl_pc2, sensor_msgs::PointCloud2 &pc2){copyPCLPointCloud2MetaData(pcl_pc2, pc2);pc2.data.swap(pcl_pc2.data);}inlinevoid toPCL(const sensor_msgs::PointCloud2 &pc2, pcl::PCLPointCloud2 &pcl_pc2){copyPointCloud2MetaData(pc2, pcl_pc2);pcl_pc2.data = pc2.data;}inlinevoid copyPointCloud2MetaData(const sensor_msgs::PointCloud2 &pc2, pcl::PCLPointCloud2 &pcl_pc2){toPCL(pc2.header, pcl_pc2.header);pcl_pc2.height = pc2.height;pcl_pc2.width = pc2.width;toPCL(pc2.fields, pcl_pc2.fields);pcl_pc2.is_bigendian = pc2.is_bigendian;pcl_pc2.point_step = pc2.point_step;pcl_pc2.row_step = pc2.row_step;pcl_pc2.is_dense = pc2.is_dense;}inlinevoid toPCL(const sensor_msgs::PointField &pf, pcl::PCLPointField &pcl_pf){pcl_pf.name = pf.name;pcl_pf.offset = pf.offset;pcl_pf.datatype = pf.datatype;pcl_pf.count = pf.count;}inlinevoid toPCL(const std::vector<sensor_msgs::PointField> &pfs, std::vector<pcl::PCLPointField> &pcl_pfs){pcl_pfs.resize(pfs.size());std::vector<sensor_msgs::PointField>::const_iterator it = pfs.begin();int i = 0;for(; it != pfs.end(); ++it, ++i) {toPCL(*(it), pcl_pfs[i]);}}inlinevoid toPCL(const std_msgs::Header &header, pcl::PCLHeader &pcl_header){toPCL(header.stamp, pcl_header.stamp);pcl_header.seq = header.seq;pcl_header.frame_id = header.frame_id;}inlinevoid toPCL(const ros::Time &stamp, std::uint64_t &pcl_stamp){pcl_stamp = stamp.toNSec() / 1000ull; // Convert from ns to us}...
}/usr/include/pcl-1.8/pcl/conversions.htemplate<typename PointT> voidtoPCLPointCloud2 (const pcl::PointCloud<PointT>& cloud, pcl::PCLPointCloud2& msg){// Ease the user's burden on specifying width/height for unorganized datasetsif (cloud.width == 0 && cloud.height == 0){msg.width = static_cast<uint32_t>(cloud.points.size ());msg.height = 1;}else{assert (cloud.points.size () == cloud.width * cloud.height);msg.height = cloud.height;msg.width = cloud.width;}// Fill point cloud binary data (padding and all)size_t data_size = sizeof (PointT) * cloud.points.size ();msg.data.resize (data_size);if (data_size){memcpy(&msg.data[0], &cloud.points[0], data_size);}// Fill fields metadatamsg.fields.clear ();for_each_type<typename traits::fieldList<PointT>::type> (detail::FieldAdder<PointT>(msg.fields));for(auto f: msg.fields) {printf("f.name %s, offset %d, datatype %d\n", f.name.c_str(), f.offset, f.datatype);}msg.header = cloud.header;msg.point_step = sizeof (PointT);msg.row_step = static_cast<uint32_t> (sizeof (PointT) * msg.width);msg.is_dense = cloud.is_dense;/// @todo msg.is_bigendian = ?;}struct FieldAdder{FieldAdder (std::vector<pcl::PCLPointField>& fields) : fields_ (fields) {};template<typename U> void operator() (){pcl::PCLPointField f;f.name = traits::name<PointT, U>::value;f.offset = traits::offset<PointT, U>::value;f.datatype = traits::datatype<PointT, U>::value;f.count = traits::datatype<PointT, U>::size;fields_.push_back (f);}std::vector<pcl::PCLPointField>& fields_;};/usr/include/pcl-1.8/pcl/point_traits.h
// offsettemplate<class PointT, typename Tag>struct offset : offset<typename POD<PointT>::type, Tag>{// Contents of specialization:// static const size_t value;// Avoid infinite compile-time recursionBOOST_MPL_ASSERT_MSG((!boost::is_same<PointT, typename POD<PointT>::type>::value),POINT_TYPE_NOT_PROPERLY_REGISTERED, (PointT&));};/usr/include/pcl-1.8/pcl/register_point_struct.h#define POINT_CLOUD_REGISTER_FIELD_OFFSET(r, name, elem) \template<> struct offset<name, pcl::fields::BOOST_PP_TUPLE_ELEM(3, 2, elem)> \{ \static const size_t value = offsetof(name, BOOST_PP_TUPLE_ELEM(3, 1, elem)); \};#define POINT_CLOUD_REGISTER_POINT_STRUCT(name, fseq) \POINT_CLOUD_REGISTER_POINT_STRUCT_I(name, \BOOST_PP_CAT(POINT_CLOUD_REGISTER_POINT_STRUCT_X fseq, 0)) \/usr/include/pcl-1.8/pcl/point_types.h
POINT_CLOUD_REGISTER_POINT_STRUCT (pcl::_PointXYZI,(float, x, x)(float, y, y)(float, z, z)(float, intensity, intensity)
)
POINT_CLOUD_REGISTER_POINT_WRAPPER(pcl::PointXYZI, pcl::_PointXYZI)/usr/include/pcl-1.8/pcl/PCLPointField.h
namespace pcl
{struct PCLPointField{PCLPointField () : name (), offset (0), datatype (0), count (0){}std::string name;pcl::uint32_t offset;pcl::uint8_t datatype;pcl::uint32_t count;enum PointFieldTypes { INT8 = 1,UINT8 = 2,INT16 = 3,UINT16 = 4,INT32 = 5,UINT32 = 6,FLOAT32 = 7,FLOAT64 = 8 };/usr/include/pcl-1.8/pcl/register_point_struct.h
自己实现类似fromROSMsg()和toROSMsg()函数功能的代码如下:
void ROSMsg2PCL(sensor_msgs::PointCloud2& ros_msgs, cloud::Ptr cloud_ptr) {cloud_ptr->header.seq = ros_msgs.header.seq;cloud_ptr->header.frame_id = ros_msgs.header.frame_id;cloud_ptr->header.stamp.fromNSec(ros_msgs->header.stamp / 1000ull); // ns => uscloud_ptr->height = ros_msgs.height;cloud_ptr->width = ros_msgs.width;cloud_ptr->is_dense = ros_msgs.is_dense;int points_num = ros_msgs.height * ros_msgs.width;cloud_ptr->points.resize(points_num * 4 * 4); // XYZIfloat * pdata = reinterpret_cast<float*>(&ros_msgs.data[0]);for (auto i = 0; i < points_num; ++i) {cloud_ptr->points[i*4 + 0] = pdata[i*4 + 0];cloud_ptr->points[i*4 + 1] = pdata[i*4 + 1];cloud_ptr->points[i*4 + 2] = pdata[i*4 + 2];if (ros_msgs.point_step == 16) // 4+4+4+4cloud_ptr->points[i*4 + 3] = pdata[i*4 + 3];/*有的雷达输出的rosmsg在fields的排放顺序有特殊安排,需要使用POINT_CLOUD_REGISTER_POINT_STRUCT注册特定的struct来读取XYZI,例如:POINT_CLOUD_REGISTER_POINT_STRUCT(OusterPointXYZIRT,(float, x, x)(float, y, y)(float, z, z)(float, intensity, intensity))即便是保证了XYZI的排放顺序,intensity可能占了8个字节,前4个字节为0后4个字节才是intensity值,不同雷达处理可能不一样,所以这里的处理只是示例,不同雷达是情况而定*/else if (ros_msgs.point_step == 20) //4+4+4+8cloud_ptr->points[i*4 + 3] = pdata[i*4 + 4];}
}void initRosMsgFields(std::vector<sensor_msgs::PointField>& fields) {fields.resize(4);fields[0].name = "x";fields[0].offset = 0;fields[0].datatype = 7;fields[0].count = 1;fields[1].name = "y";fields[1].offset = 4;fields[1].datatype = 7;fields[1].count = 1;fields[2].name = "z";fields[2].offset = 8;fields[2].datatype = 7;fields[2].count = 1;fields[3].name = "intensity";fields[3].offset = 12;fields[3].datatype = 7;fields[3].count = 1;
}void PCL2ROSMSg(cloud::Ptr cloud_ptr, sensor_msgs::PointCloud2& ros_msgs) {//set header with PCL Cloud header for common use. ros_msgs.header.stamp.fromNSec(cloud_ptr->header.stamp * 1000ull); // us => nsros_msgs.header.seq = cloud_ptr->header.seq;ros_msgs.header.frame_id = cloud_ptr->header.frame_id;initRosMsgFields(ros_msgs.fields);ros_msgs.width = cloud_ptr->width; // 1ros_msgs.height = cloud_ptr->height; // point_numros_msgs.point_step = ros_msgs.fields.size() * sizeof(float); // 4 * 4ros_msgs.row_step = static_cast<uint32_t> (ros_msgs.point_step * ros_msgs.width);ros_msgs.is_dense = cloud_ptr->is_dense;int data_size = cloud_ptr->size() * ros_msgs.point_step;if (data_size > 0) {ros_msgs.data.resize(data_size);//memcpy(&ros_msgs.data[0], &cloud_ptr->points[0], data_size);float * pdata = reinterpret_cast<float*>(&ros_msgs.data[0]);for (int i = 0; i < cloud_ptr->size(); i++ ) {pcl::PointXYZI pt = cloud_ptr->points[i];pdata[i*4 + 0] = pt.x;pdata[i*4 + 1] = pt.y;pdata[i*4 + 2] = pt.z;pdata[i*4+ 3] = pt.intensity;}}
}