markers_from_tf.py

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#!/usr/bin/env python

"""
    Convert a skeleton transform tree to a list of visualization markers for RViz.
        
    Created for the Pi Robot Project: http://www.pirobot.org
    Copyright (c) 2011 Patrick Goebel.  All rights reserved.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details at:
    
    http://www.gnu.org/licenses/gpl.html
"""

import rospy
from visualization_msgs.msg import Marker
from geometry_msgs.msg import Point
import tf

class SkeletonMarkers():
    def __init__(self):
        rospy.init_node('markers_from_tf')
                
        rospy.loginfo("Initializing Skeleton Markers Node...")
        
        rate = rospy.get_param('~rate', 20)
        r = rospy.Rate(rate)
        
        # There is usually no need to change the fixed frame from the default
        self.fixed_frame = rospy.get_param('~fixed_frame', 'openni_depth_frame')
        
        # Get the list of skeleton frames we want to track
        self.skeleton_frames = rospy.get_param('~skeleton_frames', '')

        # Initialize the tf listener
        tf_listener = tf.TransformListener()
        
        # Define a marker publisher
        marker_pub = rospy.Publisher('skeleton_markers', Marker, queue_size=5)
        
        # Intialize the markers
        self.initialize_markers()
        
        # Make sure we see the openni_depth_frame
        tf_listener.waitForTransform(self.fixed_frame, self.fixed_frame, rospy.Time(), rospy.Duration(60.0))
        
        # A flag to track when we have detected a skeleton
        skeleton_detected = False
        
        # Begin the main loop
        while not rospy.is_shutdown():
            # Set the markers header
            self.markers.header.stamp = rospy.Time.now()
                        
            # Clear the markers point list
            self.markers.points = list()
            
            # Check to see if a skeleton is detected
            while not skeleton_detected: 
                # Assume we can at least see the head frame               
                frames = [f for f in tf_listener.getFrameStrings() if f.startswith('head_')]
                
                try:
                    # If the head frame is visible, pluck off the
                    # user index from the name
                    head_frame = frames[0]
                    user_index = head_frame.replace('head_', '')
                    
                    # Make sure we have a transform between the head
                    # and the fixed frame
                    try:
                        (trans, rot)  = tf_listener.lookupTransform(self.fixed_frame, head_frame, rospy.Time(0))
                        skeleton_detected = True

                    except (tf.Exception, tf.ConnectivityException, tf.LookupException):
                        skeleton_detected = False
                        rospy.loginfo("User index: " + str(user_index))
                        r.sleep()
                except:
                    skeleton_detected = False
            
            # Loop through the skeleton frames
            for frame in self.skeleton_frames:
                # Append the user_index to the frame name
                skel_frame = frame + "_" + str(user_index)

                # We only need the origin of each skeleton frame
                # relative to the fixed frame
                position = Point()
                                        
                # Get the transformation from the fixed frame
                # to the skeleton frame
                try:
                    (trans, rot)  = tf_listener.lookupTransform(self.fixed_frame, skel_frame, rospy.Time(0))
                    position.x = trans[0]
                    position.y = trans[1]
                    position.z = trans[2]
                                                            
                    # Set a marker at the origin of this frame
                    self.markers.points.append(position)
                except:
                    pass
                
            # Publish the set of markers
            marker_pub.publish(self.markers)
                              
            r.sleep()
            
    def initialize_markers(self):
        # Set various parameters
        scale = rospy.get_param('~scale', 0.07)
        lifetime = rospy.get_param('~lifetime', 0) # 0 is forever
        ns = rospy.get_param('~ns', 'skeleton_markers')
        id = rospy.get_param('~id', 0)
        color = rospy.get_param('~color', {'r': 0.0, 'g': 1.0, 'b': 0.0, 'a': 1.0})
        
        # Initialize the marker points list
        self.markers = Marker()
        self.markers.header.frame_id = self.fixed_frame
        self.markers.ns = ns
        self.markers.id = id
        self.markers.type = Marker.POINTS
        self.markers.action = Marker.ADD
        self.markers.lifetime = rospy.Duration(lifetime)
        self.markers.scale.x = scale
        self.markers.scale.y = scale
        self.markers.color.r = color['r']
        self.markers.color.g = color['g']
        self.markers.color.b = color['b']
        self.markers.color.a = color['a']
        
if __name__ == '__main__':
    try:
        SkeletonMarkers()
    except rospy.ROSInterruptException:
        pass