.. _alvisionrecognition-tuto:

ALVisionRecognition Tutorial
============================

:ref:`Overview <alvisionrecognition>` | :ref:`API <alvisionrecognition-api>` | Tutorial


Introduction
------------

This tutorial explains how to access the ALVisionRecognition module from Python. The module is designed to notify subscribers when a previously learned image has been recognized.

To receive the notification, we need to create a module that exposes a callback method.

.. note::

   You might not have this module depending on your distribution.
   This module should be loaded on the robot's NAOqi.


Getting a proxy to ALVisionRecognition
--------------------------------------

After some initialization steps, we first instantiate a proxy to the ALVisionRecognition module.

Prepare some imports and variables

.. code-block:: python

  import os
  import sys
  import time
  import naoqi
  from naoqi import *
  
  # A global counter of the number of loops
  count = 10
  
  PC_IP = "127.0.0.1"  # Replace this with your computer's IP address
  NAO_IP = "nao.local" # Replace this with your NAOqi's IP address

  # The name of the event generated by ALVisionRecognition
  event_name = "PictureDetected"


We create a python module with a callback method and instatiate it

.. code-block:: python

  # The name of our local python module
  module_name = "python_module"
  
  class myModule(ALModule):
  """python class myModule test auto documentation"""
  
    def dataChanged(self, strVarName, value, strMessage):
      """callback when data change"""
      
      print "datachanged", strVarName, " ", value, " ", strMessage
      global count
      count = count - 1
  
  # Create a local broker, connected to the remote naoqi
  broker = ALBroker("pythonBroker", PC_IP, 9999, NAO_IP, 9559)
  
  # Create a python module
  pythonModule = myModule(module_name)

We subscribe to event so that our callback can be called

.. code-block:: python

  try:
    # Create a proxy to ALMemory
    memoryProxy = ALProxy("ALMemory", NAO_IP, PORT)
    
    # Subscribe to the event, saying where we want to be called back
    memoryProxy.subscribeToEvent(event_name, module_name, "dataChanged")

    # Let the picture recognition run
    while count > 0:
      time.sleep(5)
    
    # Unsubscribe
    memoryProxy.unsubscribeToEvent(event_name, module_name)
    
  except RuntimeError, e:
    print e
    exit(1)
  
  print 'end'