[PCLVisualizer] Render to png, and then convert it to cv::Mat

render_to_mat.cpp

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/visualization/pcl_visualizer.h>

#include <vtkActor.h>
#include <vtkPNGWriter.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkWindowToImageFilter.h>

#include <opencv2/opencv.hpp>

std::vector<unsigned char>
renderToVec(vtkSmartPointer<vtkRenderWindow> &renderWindow) {
  renderWindow->Render();
  vtkSmartPointer<vtkWindowToImageFilter> windowToImageFilter =
      vtkSmartPointer<vtkWindowToImageFilter>::New();
  windowToImageFilter->SetInput(renderWindow);
  windowToImageFilter->Update();
  vtkSmartPointer<vtkPNGWriter> writer = vtkSmartPointer<vtkPNGWriter>::New();
  writer->SetWriteToMemory(1);
  writer->SetInputConnection(windowToImageFilter->GetOutputPort());
  writer->Write();
  auto rawPngBuffer = writer->GetResult();
  auto rawPointer = rawPngBuffer->GetPointer(0);
  auto total_size =
      rawPngBuffer->GetDataSize() * rawPngBuffer->GetDataTypeSize();
  std::vector<unsigned char> buffer(rawPointer, rawPointer + total_size);
  return buffer;
}

int main() {
  auto cloud =
      pcl::PointCloud<pcl::PointXYZ>::Ptr(new pcl::PointCloud<pcl::PointXYZ>);
  assert(pcl::io::loadPCDFile("table_scene_lms400.pcd", *cloud) == 0);

  auto viewer = pcl::visualization::PCLVisualizer::Ptr(
      new pcl::visualization::PCLVisualizer("Test", false));

  viewer->addPointCloud(cloud, "test");

  auto renderWindow = viewer->getRenderWindow();
  auto buf = renderToVec(renderWindow);
  cv::Mat mat = cv::imdecode(buf, 1);

  std::cout << buf.size() << std::endl;
  std::cout << mat.rows << " " << mat.cols << std::endl;

  // comment out if unneccesarry
  cv::imshow("Test with cv::Mat", mat);
  cv::waitKey(0);

  return 0;
}

Result:

Very good!! Thank you.