Compressing/Decompressing

On the other hand, this is the code needed to compress and decompress a point cloud with PCL: 

#include <pcl/io/pcd_io.h>
#include <pcl/compression/octree_pointcloud_compression.h>
#include <boost/thread/thread.hpp>
#include <pcl/visualization/pcl_visualizer.h>

int
main(int argc, char** argv)
{
	// Objects for storing the point clouds.
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::PointCloud<pcl::PointXYZ>::Ptr decompressedCloud(new pcl::PointCloud<pcl::PointXYZ>);

	// Read a PCD file from disk.
	if (pcl::io::loadPCDFile<pcl::PointXYZ>(argv[1], *cloud) != 0)
	{
		return -1;
	}

	// Octree compressor object.
	// Check /usr/include/pcl-<version>/pcl/compression/compression_profiles.h for more profiles.
	// The second parameter enables the output of information.
	pcl::io::OctreePointCloudCompression<pcl::PointXYZ> octreeCompression(pcl::io::MED_RES_ONLINE_COMPRESSION_WITHOUT_COLOR, true);
	// Stringstream that will hold the compressed cloud.
	std::stringstream compressedData;

	// Compress the cloud (you would save the stream to disk).
	octreeCompression.encodePointCloud(cloud, compressedData);

	// Decompress the cloud.
	octreeCompression.decodePointCloud(compressedData, decompressedCloud);

	// Display the decompressed cloud.
	boost::shared_ptr<pcl::visualization::PCLVisualizer> viewer(new pcl::visualization::PCLVisualizer("Octree compression"));
	viewer->addPointCloud<pcl::PointXYZ>(decompressedCloud, "cloud");
	while (!viewer->wasStopped())
	{
		viewer->spinOnce(100);
		boost::this_thread::sleep(boost::posix_time::microseconds(100000));
	}
}


  • Original point cloud.

  • Point cloud retrieved after octree compression.


As you can see, the process has decreased the amount of points in the cloud. The default parameters of the "OctreePointCloudCompression" object establish an octree resolution (at lowest level) of 1cm, and a coordinate precision of 1mm. These values can of course be changed to suit your needs, but simplifying the cloud in this way is an useful operation that we will cover later.