通过fromPCLPointCloud2将PointCloud<RGB.>,然后通过savePNGFile保存文件。
代码如下：

#include <pcl/io/pcd_io.h>
#include <pcl/console/print.h>
#include <pcl/console/parse.h>
#include <pcl/console/time.h>
#include <pcl/io/png_io.h>

using namespace pcl;
using namespace pcl::io;
using namespace pcl::console;

void
printHelp (int, char **argv)
{
  print_error ("Syntax is: %s input.pcd output.png\n", argv[0]);
}

bool
loadCloud (const std::string &filename, pcl::PCLPointCloud2 &cloud)
{
  TicToc tt;
  print_highlight ("Loading "); print_value ("%s ", filename.c_str ());

  tt.tic ();
  if (loadPCDFile (filename, cloud) < 0)
    return (false);
  print_info ("[done, "); print_value ("%g", tt.toc ()); print_info (" ms : "); print_value ("%d", cloud.width * cloud.height); print_info (" points]\n");
  print_info ("Available dimensions: "); print_value ("%s\n", pcl::getFieldsList (cloud).c_str ());

  return (true);
}

void
saveImage (const std::string &filename, const PointCloud<RGB> &image)
{
  TicToc tt;
  tt.tic ();

  print_highlight ("Saving "); print_value ("%s ", filename.c_str ());
  io::savePNGFile (filename, image, "rgb");

  print_info ("[done, "); print_value ("%g", tt.toc ()); print_info (" ms : "); print_value ("%d", image.width * image.height); print_info (" points]\n");
}

/* ---[ */
int
main (int argc, char** argv)
{
  print_error ("This tool is deprecated, please use \"pcl_pcd2png\" instead!\n");
  print_info ("Convert the RGB information of an organized PCD file to a PNG image. For more information, use: %s -h\n", argv[0]);

  if (argc < 3)
  {
    printHelp (argc, argv);
    return (-1);
  }

  // Parse the command line arguments for .pcd files
  std::vector<int> pcd_file_indices = parse_file_extension_argument (argc, argv, ".pcd");
  if (pcd_file_indices.size () != 1)
  {
    print_error ("Need one input PCD file and one output PNG file.\n");
    return (-1);
  }

  std::vector<int> png_file_indices = parse_file_extension_argument (argc, argv, ".png");
  if (png_file_indices.size () != 1)
  {
    print_error ("Need one input PCD file and one output PNG file.\n");
    return (-1);
  }

  // Load the first file
  pcl::PCLPointCloud2 cloud;
  if (!loadCloud (argv[pcd_file_indices[0]], cloud))
    return (-1);


  PointCloud<RGB> image;
  fromPCLPointCloud2 (cloud, image);


  // Check if the cloud is organized
  if (!image.isOrganized ())
  {
    PCL_ERROR ("Input cloud is not organized.\n");
    return (-1);
  }

  // Save cloud
  saveImage (argv[png_file_indices[0]], image);

  return (0);
}

来源：PCL官方示例