Getting an image

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The aim of this example is to show how to retrieve images from NAO’s cameras. The images will be displayed in a window, using OpenCV library. Press ESC to exit the application.

The whole example is available here: getimage.zip

Source file:

getimages.cpp

/**
 *
 * This example demonstrates how to get images from the robot remotely and how
 * to display them on your screen using opencv.
 *
 * Copyright Aldebaran Robotics
 */

// Aldebaran includes.
#include <alproxies/alvideodeviceproxy.h>
#include <alvision/alimage.h>
#include <alvision/alvisiondefinitions.h>
#include <alerror/alerror.h>

// Opencv includes.
#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>


#include <iostream>
#include <string>

using namespace AL;


/**
* \brief Shows images retrieved from the robot.
*
* \param robotIp the IP adress of the robot
*/
void showImages(const std::string& robotIp)
{
  /** Create a proxy to ALVideoDevice on the robot.*/
  ALVideoDeviceProxy camProxy(robotIp, 9559);

  /** Subscribe a client image requiring 320*240 and BGR colorspace.*/
  const std::string clientName = camProxy.subscribe("test", kQVGA, kBGRColorSpace, 30);

  /** Create an cv::Mat header to wrap into an opencv image.*/
  cv::Mat imgHeader = cv::Mat(cv::Size(320, 240), CV_8UC3);

  /** Create a OpenCV window to display the images. */
  cv::namedWindow("images");

  /** Main loop. Exit when pressing ESC.*/
  while ((char) cv::waitKey(30) != 27)
  {
    /** Retrieve an image from the camera.
    * The image is returned in the form of a container object, with the
    * following fields:
    * 0 = width
    * 1 = height
    * 2 = number of layers
    * 3 = colors space index (see alvisiondefinitions.h)
    * 4 = time stamp (seconds)
    * 5 = time stamp (micro seconds)
    * 6 = image buffer (size of width * height * number of layers)
    */
    ALValue img = camProxy.getImageRemote(clientName);

    /** Access the image buffer (6th field) and assign it to the opencv image
    * container. */
    imgHeader.data = (uchar*) img[6].GetBinary();

    /** Tells to ALVideoDevice that it can give back the image buffer to the
    * driver. Optional after a getImageRemote but MANDATORY after a getImageLocal.*/
    camProxy.releaseImage(clientName);

    /** Display the iplImage on screen.*/
    cv::imshow("images", imgHeader);
  }

  /** Cleanup.*/
  camProxy.unsubscribe(clientName);
}



int main(int argc, char* argv[])
{
  if (argc < 2)
  {
    std::cerr << "Usage 'getimages robotIp'" << std::endl;
    return 1;
  }

  const std::string robotIp(argv[1]);

  try
  {
    showImages(robotIp);
  }
  catch (const AL::ALError& e)
  {
    std::cerr << "Caught exception " << e.what() << std::endl;
  }

  return 0;
}

CMakeLists.txt:

The corresponding CMakeLists.txt file is the following:

CMakeLists.txt

##
# Copyright (C) 2010 Aldebaran Robotics

cmake_minimum_required(VERSION 2.6.4 FATAL_ERROR)
project(getimages)
# this lets you find the qibuild cmake frameworl
find_package(qibuild)


# Here, we create an executable named "getimages" from the cpp file.
qi_create_bin(getimages getimages.cpp)

# Here we say that our executable depends on
# - ALCOMMON (main naoqi lib)
# - ALPROXIES (using specialized naoqi proxies)
# - ALVISION (for vision definitions)
# - OPENCV (display)
#
# It automatically links with the corresponding libraries and make their headers
# available.
qi_use_lib(getimages ALCOMMON ALPROXIES ALVISION OPENCV3_CORE OPENCV3_HIGHGUI)

Warning

Please read Using OpenCV before trying to use this example on your desktop if you are using linux.