Example to demonstrate use of PointCloud2 count field

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.3)
project(test_pointcloud_count)

## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  roscpp
  pcl_ros
  pcl_conversions
)

find_package(PCL 1.7 REQUIRED REQUIRED)
include_directories(${PCL_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})


###################################
## catkin specific configuration ##
###################################
## The catkin_package macro generates cmake config files for your package
## Declare things to be passed to dependent projects
## INCLUDE_DIRS: uncomment this if you package contains header files
## LIBRARIES: libraries you create in this project that dependent projects also need
## CATKIN_DEPENDS: catkin_packages dependent projects also need
## DEPENDS: system dependencies of this project that dependent projects also need
catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES test_pointcloud_count
#  CATKIN_DEPENDS roscpp
#  DEPENDS system_lib
)

###########
## Build ##
###########

## Specify additional locations of header files
## Your package locations should be listed before other locations
# include_directories(include)
include_directories(
  ${catkin_INCLUDE_DIRS}
)

## Declare a C++ executable
add_executable(count_test_node count_test_node.cpp)

## Add cmake target dependencies of the executable
add_dependencies(count_test_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against
target_link_libraries(count_test_node
  ${catkin_LIBRARIES}
  ${PCL_LIBRARIES}
)

#############
## Install ##
#############

## Mark executables and/or libraries for installation
install(TARGETS count_test_node
  ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
  LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
  RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
)

count_test_node.cpp

/*
 * Copyright (C) 2016, DFKI GmbH
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of DFKI GmbH nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *      Authors:
 *         Martin Günther <martin.guenther@dfki.de>
 *
 */

#include <ros/ros.h>

#include <pcl_conversions/pcl_conversions.h>

#include <sensor_msgs/PointCloud2.h>
#include <pcl_ros/point_cloud.h>

typedef pcl::FPFHSignature33 PointT;
typedef pcl::PointCloud<PointT> PointCloudT;

int main(int argc, char **argv)
{
  ros::init(argc, argv, "count_test_node");
  ros::NodeHandle nh;

  ros::Publisher pub = nh.advertise<PointCloudT>("cloud", 1);

  ROS_INFO("initialized");
  ros::Rate r(10);
  while (ros::ok())
  {
    PointCloudT::Ptr cloud = boost::make_shared<PointCloudT>();
    cloud->header.frame_id = "some_frame";
    cloud->header.stamp = ros::Time::now().toNSec() / 1000;

    cloud->width = 1;
    cloud->height = 1;
    cloud->is_dense = true;

    PointT p;
    size_t count = sizeof(p.histogram) / sizeof(float);  // == 33
    for (size_t i = 0; i < count; ++i)
    {
      // need to initialize data
      p.histogram[i] = 0.f;
    }
    p.histogram[15] = 23.42f;

    cloud->points.push_back(p);

    pub.publish(cloud);

    ros::spinOnce();
    r.sleep();
  }

  return 0;
}

package.xml

<?xml version="1.0"?>
<package format="2">
  <name>test_pointcloud_count</name>
  <version>0.0.0</version>
  <description>Example to demonstrate use of PointCloud2 count field</description>

  <maintainer email="martin.guenther@dfki.de">Martin Günther</maintainer>
  <author email="martin.guenther@dfki.de">Martin Günther</author>

  <license>BSD</license>

  <buildtool_depend>catkin</buildtool_depend>

  <depend>roscpp</depend>
  <depend>pcl_ros</depend>
  <depend>libpcl-all-dev</depend>
</package>