（十七）从测距图像中提取边界

Object(Obstacle) border：属于物体的最外面的可见点；

Shadow border：背景中与物体相邻的点；

Veil points：Object border和Shadow border之间的插值点。

以下代码实现将点云投影为距离图像，然后再从距离图像中提取点云的边界。

range_image_border_extraction.cpp

/* \author Bastian Steder */
#include <iostream>
#include <pcl/range_image/range_image.h>
#include <pcl/io/pcd_io.h>
#include <pcl/visualization/range_image_visualizer.h>
#include <pcl/visualization/pcl_visualizer.h>
#include <pcl/features/range_image_border_extractor.h>
#include <pcl/console/parse.h>
#include <pcl/common/file_io.h> // for getFilenameWithoutExtension

typedef pcl::PointXYZ PointType;

// --------------------
// -----Parameters-----
// --------------------
float angular_resolution = 0.5f;
pcl::RangeImage::CoordinateFrame coordinate_frame = pcl::RangeImage::CAMERA_FRAME;
bool setUnseenToMaxRange = false;

// --------------
// -----Help-----
// --------------
void printUsage (const char* progName)
{
  std::cout << "\n\nUsage: "<<progName<<" [options] <scene.pcd>\n\n"
            << "Options:\n"
            << "-------------------------------------------\n"
            << "-r <float>   angular resolution in degrees (default "<<angular_resolution<<")\n"
            << "-c <int>     coordinate frame (default "<< (int)coordinate_frame<<")\n"
            << "-m           Treat all unseen points to max range\n"
            << "-h           this help\n"
            << "\n\n";
}

// --------------
// -----Main-----
// --------------
int main (int argc, char** argv)
{
      // --------------------------------------
      // -----Parse Command Line Arguments-----
      // --------------------------------------
      if (pcl::console::find_argument (argc, argv, "-h") >= 0)
      {
            printUsage (argv[0]);
            return 0;
      }
      if (pcl::console::find_argument (argc, argv, "-m") >= 0)
      {
            setUnseenToMaxRange = true;
            std::cout << "Setting unseen values in range image to maximum range readings.\n";
      }
      int tmp_coordinate_frame;
      if (pcl::console::parse (argc, argv, "-c", tmp_coordinate_frame) >= 0)
      {
            coordinate_frame = pcl::RangeImage::CoordinateFrame (tmp_coordinate_frame);
            std::cout << "Using coordinate frame "<< (int)coordinate_frame<<".\n";
      }
      if (pcl::console::parse (argc, argv, "-r", angular_resolution) >= 0)
            std::cout << "Setting angular resolution to "<<angular_resolution<<"deg.\n";
      angular_resolution = pcl::deg2rad (angular_resolution);

      // ------------------------------------------------------------------
      // -----Read pcd file or create example point cloud if not given-----
      // ------------------------------------------------------------------
      pcl::PointCloud<PointType>::Ptr point_cloud_ptr (new pcl::PointCloud<PointType>);
      pcl::PointCloud<PointType>& point_cloud = *point_cloud_ptr;
      pcl::PointCloud<pcl::PointWithViewpoint> far_ranges;
      Eigen::Affine3f scene_sensor_pose (Eigen::Affine3f::Identity ());
      std::vector<int> pcd_filename_indices = pcl::console::parse_file_extension_argument (argc, argv, "pcd");
      if (!pcd_filename_indices.empty ())
      {
            std::string filename = argv[pcd_filename_indices[0]];
            if (pcl::io::loadPCDFile (filename, point_cloud) == -1)
            {
                  std::cout << "Was not able to open file \""<<filename<<"\".\n";
                  printUsage (argv[0]);
                  return 0;
            }
      scene_sensor_pose = Eigen::Affine3f (Eigen::Translation3f (point_cloud.sensor_origin_[0],
                                                                  point_cloud.sensor_origin_[1],
                                                                  point_cloud.sensor_origin_[2]))* 
                                                                  Eigen::Affine3f (point_cloud.sensor_orientation_); 
      //


      std::string far_ranges_filename = pcl::getFilenameWithoutExtension (filename)+"_far_ranges.pcd";   "_far_ranges.pcd";
      if (pcl::io::loadPCDFile(far_ranges_filename.c_str(), far_ranges) == -1)
            std::cout << "Far ranges file \""<<far_ranges_filename<<"\" does not exists.\n";
      }
      else
      {
            std::cout << "\nNo *.pcd file given => Generating example point cloud.\n\n";
            for (float x=-0.5f; x<=0.5f; x+=0.01f)
            {
                  for (float y=-0.5f; y<=0.5f; y+=0.01f)
                  {
                        PointType point;  point.x = x;  point.y = y;  point.z = 2.0f - y;
                        point_cloud.push_back (point);
                  }
            }
                  point_cloud.width = point_cloud.size ();  point_cloud.height = 1;
      }

      // -----------------------------------------------
      // -----Create RangeImage from the PointCloud-----
      // -----------------------------------------------
      float noise_level = 0.0;
      float min_range = 0.0f;
      int border_size = 1;
      pcl::RangeImage::Ptr range_image_ptr (new pcl::RangeImage);
      pcl::RangeImage& range_image = *range_image_ptr;   
      range_image.createFromPointCloud (point_cloud, angular_resolution, pcl::deg2rad (360.0f), pcl::deg2rad (180.0f),
                                    scene_sensor_pose, coordinate_frame, noise_level, min_range, border_size);
      range_image.integrateFarRanges (far_ranges);
      if (setUnseenToMaxRange)
      	range_image.setUnseenToMaxRange ();

      // --------------------------------------------
      // -----Open 3D viewer and add point cloud-----
      // --------------------------------------------
      pcl::visualization::PCLVisualizer viewer ("3D Viewer");
      viewer.setBackgroundColor (1, 1, 1);
      viewer.addCoordinateSystem (0.5f,  scene_sensor_pose);
      pcl::visualization::PointCloudColorHandlerCustom<PointType> point_cloud_color_handler (point_cloud_ptr, 0, 0, 0);
      viewer.addPointCloud (point_cloud_ptr, point_cloud_color_handler, "original point cloud");
      //PointCloudColorHandlerCustom<pcl::PointWithRange> range_image_color_handler (range_image_ptr, 150, 150, 150);
      //viewer.addPointCloud (range_image_ptr, range_image_color_handler, "range image");
      //viewer.setPointCloudRenderingProperties (PCL_VISUALIZER_POINT_SIZE, 2, "range image");

      // -------------------------
      // -----提取边界-----
      // -------------------------
      pcl::RangeImageBorderExtractor border_extractor (&range_image);
      pcl::PointCloud<pcl::BorderDescription> border_descriptions;
      border_extractor.compute (border_descriptions);

      // ----------------------------------
      // -----Show points in 3D viewer-----
      // ----------------------------------
      // object border, veil points 和shadow points
      pcl::PointCloud<pcl::PointWithRange>::Ptr border_points_ptr(new pcl::PointCloud<pcl::PointWithRange>),
                                                veil_points_ptr(new pcl::PointCloud<pcl::PointWithRange>),
                                                shadow_points_ptr(new pcl::PointCloud<pcl::PointWithRange>);
      pcl::PointCloud<pcl::PointWithRange>& border_points = *border_points_ptr,
                                          & veil_points = * veil_points_ptr,
                                          & shadow_points = *shadow_points_ptr;
      // 不同类型的点
      for (int y=0; y< (int)range_image.height; ++y)
      {
            for (int x=0; x< (int)range_image.width; ++x)
            {        
                  if (border_descriptions[y*range_image.width + x].traits[pcl::BORDER_TRAIT__OBSTACLE_BORDER])
                        border_points.push_back (range_image[y*range_image.width + x]);
                  if (border_descriptions[y*range_image.width + x].traits[pcl::BORDER_TRAIT__VEIL_POINT])
                        veil_points.push_back (range_image[y*range_image.width + x]);
                  if (border_descriptions[y*range_image.width + x].traits[pcl::BORDER_TRAIT__SHADOW_BORDER])
                        shadow_points.push_back (range_image[y*range_image.width + x]);
            }
      }
      // 对不同类型的点采用不同颜色可视化
      pcl::visualization::PointCloudColorHandlerCustom<pcl::PointWithRange> border_points_color_handler (border_points_ptr, 0, 255, 0);
      viewer.addPointCloud<pcl::PointWithRange> (border_points_ptr, border_points_color_handler, "border points");
      viewer.setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 5, "border points");

      pcl::visualization::PointCloudColorHandlerCustom<pcl::PointWithRange> veil_points_color_handler (veil_points_ptr, 255, 0, 0);
      viewer.addPointCloud<pcl::PointWithRange> (veil_points_ptr, veil_points_color_handler, "veil points");
      viewer.setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 5, "veil points");

      pcl::visualization::PointCloudColorHandlerCustom<pcl::PointWithRange> shadow_points_color_handler (shadow_points_ptr, 0, 255, 255);
      viewer.addPointCloud<pcl::PointWithRange> (shadow_points_ptr, shadow_points_color_handler, "shadow points");
      viewer.setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 5, "shadow points");

      //-------------------------------------
      // -----Show points on range image-----
      // ------------------------------------
      pcl::visualization::RangeImageVisualizer* range_image_borders_widget = NULL;
      range_image_borders_widget =
      pcl::visualization::RangeImageVisualizer::getRangeImageBordersWidget (range_image, -std::numeric_limits<float>::infinity (), std::numeric_limits<float>::infinity (), false,
                                                                              border_descriptions, "Range image with borders");
      // -------------------------------------


      //--------------------
      // -----Main loop-----
      //--------------------
      while (!viewer.wasStopped ())
      {
	      range_image_borders_widget->spinOnce ();
	      viewer.spinOnce ();
	      pcl_sleep(0.01);
      }
}

CmakeLists.txt

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

project(range_image_border_extraction)

find_package(PCL 1.3 REQUIRED)

include_directories(${PCL_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})

add_executable (range_image_border_extraction range_image_border_extraction.cpp)
target_link_libraries (range_image_border_extraction ${PCL_LIBRARIES})

编译并运行:

./range_image_border_extraction -m

指定点云:

./range_image_border_extraction table_scene_lms400.pcd  -m -r 0.4 -c 1

绿点为object border; 红色为veil points; 蓝色为shadow border

数据样本

官方文档