Human gesture detection

Overview

signal_cellular_alt  Level:  Intermediate
track_changes  Goal:  learn how to detect Human gesture expressions with QTrobot Nuitrack interface
task_alt  Requirements:

•   Quick start with coding on QTrobot
•   Create a ROS python project
•   QTrobot interfaces using ROS Topics
•   QTrobot interfaces using ROS Subscribers

In this tutorial we will learn about how to read human gestures with QTrobot Nuitrack interface and react to them.

Create a python project

First we create a python project for our tutorial. let's call it tutorial_qt_subscribe and add the required python file:

cd ~/catkin_ws/src
catkin_create_pkg tutorial_qt_gestures rospy roscpp -D "Reading human gestures movement"
cd tutorial_qt_gestures/src
touch tutorial_qt_gestures_node.py
chmod +x tutorial_qt_gestures_node.py

Code

Open the tutorial_qt_gestures_node.py file and add the following code:

#!/usr/bin/env python
import sys
import rospy
from qt_gesture_controller.srv import gesture_play
from qt_nuitrack_app.msg import Gestures

def gesture_callback(msg):
    if msg.gestures[0].name == "SWIPE RIGHT":
        gesturePlay("QT/swipe_right",0)
    elif msg.gestures[0].name == "SWIPE LEFT":
        gesturePlay("QT/swipe_left",0)

if __name__ == '__main__':
    rospy.init_node('my_tutorial_node')
    rospy.loginfo("my_tutorial_node started!")

    gesturePlay = rospy.ServiceProxy('/qt_robot/gesture/play', gesture_play)
    # define ros subscriber
    rospy.Subscriber('/qt_nuitrack_app/gestures', Gestures, gesture_callback)
   
    try:
        rospy.spin()
    except KeyboardInterrupt:
        pass

    rospy.loginfo("finsihed!")

Explanation

First we imported Gestures message type from qt_nuitrack_app.msg message library. This message type is used in communication with /qt_nuitrack_app/gestures.

Tip

How do we know which messages an interface uses? well, There is a useful command in ROS which tells you that:

rostopic info /qt_nuitrack_app/gestures
Type: qt_nuitrack_app/Gestures
...

Then we created a subscriber for/qt_nuitrack_app/gestures with callback function gesture_callback. In the callback we react accordingly to what is detected. If we detect gesture "SWIPE RIGHT" we also play a gesture "swipe_right". That will make QTrobot repeat your gestures.

def gesture_callback(msg):
    if msg.gestures[0].name == "SWIPE RIGHT":
        gesturePlay("QT/swipe_right",0)
    elif msg.gestures[0].name == "SWIPE LEFT":
        gesturePlay("QT/swipe_left",0)

Stand in front of QTrobot and do one of the gestures "SWIPE LEFT" or "SWIPE RIGHT". When QTrobot detects the gesture, it will repeat the same pre-recorded gesture.