main.py

# -*- coding: utf-8 -*-
import cv2
import time
import config

from collections import namedtuple
from math        import atan, sqrt

"""
Slouchy uses your webcam to determine if you are slouching and alerts you when
you are. This project is still in active development and not feature complete.

Example:
    $ ./slouchy.py [arguments]

Arguments (unimplemented):
    -t, --text-mode    Put slouchy in text mode, disabling all GUI features.
    -g, --gui          Put slouchy in GUI mode (the default). GUI mode normally
                       detaches slouchy from the terminal.
    -h, --help         Print a help message, then terminate.

Attributes:
    config (configobj.ConfigObj): Used to access slouchy's config file. All
        other module level variable get their values from there.
    distance_reference (float): The distance value for the subject when sitting
        upright.
    thoracolumbar_tolerance (float): The ammount of deviation from the
        reference which will be tolerated before reporting the subject is
        slouching.
    cervical_tolerance (float): The amount lateral flexion of the cervical
        before assuming slouching. Note: this and a few other values will be
        integrated into a single model to better discern slouching.
    face_cascade_path (str): The path for the face cascade classifier.
    eye_cascade_path (str): The path for the eye cascade classifier.
    camera_warm_up (int): The Δtime needed for the user camera to initialize.

Modules communicate with named tuples called Maybe. It is designed to emulate
the behavior of Maybe/Either constructs in functional languages.

success (Bool): Indicates whether a given call was successful.

result (Bool/Str): If success is true, result provides accompanying information
                   which is useful or necessary for future calculations.
                   If success is false, result will be a string containing an
                   error message.
"""

# Some pseudo-functional programming here: use of namedtuples to simulate the
# Maybe/Either construct throughout this program. Success is always True or
# False, indicating whether a requested action has succeeded. If success is
# True, result contains the calculation results. Otherwise, result contains an
# error message
Maybe = namedtuple('Maybe', ['success','result'])

cap           = cv2.VideoCapture(config.video_device)
camera_width  = float(cap.get(3))
camera_height = float(cap.get(4))

if config.text_mode:
  print('Camera field of view: {} high, {} wide'
          .format(camera_height, int(camera_width)))
cap.release()


def determine_distance(MaybeFace):
  """
  Use height and width information of face to find its distance from the camera.

  This uses the in-frame height and width of the face previously captured by the
  camera to as the leg and base of a right triangle. Using a² + b² = c², the
  distance of the face from the camera is determined, in abstract terms. The
  numbers produced are not used to determine distance in any real-world unit.
  All that matters here are the relationships.

  Args:
      MaybeFace tuple: Containing success status, and results.
                       If successful, results contain the x, y, width, and height of the
                       region in the previously taken image determined to depict a face.
  Returns:
      MaybeDistance tuple: The face-camera distance on success, error message on failure.
  """
  if MaybeFace.success:
    (x, y, w, h) = MaybeFace.result
  else:
    return MaybeFace

  if config.text_mode:
    print('Face detected')
    print('-------------')
    print('    Position:   x = {:d}, y = {:d}'.format(x, y))
    print('    Dimensions: w = {:d}, h = {:d}'.format(w, h))

  distance = sqrt(y**2 + w**2)

  return Maybe(True, distance)

def get_face_width(MaybeFace):
  if MaybeFace.success:
    (x, y, w, h) = MaybeFace.result
  else:
    return MaybeFace

  (x, y, w, h) = MaybeFace.result
  return Maybe(True, w)


# Take a picture with the camera.
# Ideally this is where we always transition from the impure to "pure" calculations.
# video_device -> MaybeImage
def take_picture(video_device):
  """
  Open indicated camera, caputure a frame from it, and return an image.

  Args:
      video_device: The camera which should be available for use.

  Returns:
      Maybe tuple((bool, [int]) or (bool, str)): True and a greyscaled version
      of the captured image. False and a string containing an error message
      indicating a camera failure.
  """
  cap = cv2.VideoCapture(video_device)

  if config.camera_warm_up > 0: # Some cameras need to be given worm up time
    time.sleep(config.camera_warm_up)

  if not cap.isOpened():
    exit('Failed to open camera. Please make sure video_device is set \
correctly.')

  ret, image = cap.read()      # Grab and decode frame from the camera

  if not ret:
    return Maybe(False, 'Camera unexpectedly disconnected.')

  # Make image grayscale for processing
  gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

  return Maybe(True, gray_image)


# MaybeImage -> MaybePosture
def determine_posture(MaybeImage):
  if MaybeImage.success:
    image = MaybeImage.result
  else:
    return MaybeImage

  # TODO: Factor this out or something? I don't like this...
  maybe_face = detect_face(MaybeImage)
  if maybe_face.success:
    x, y, w, h = maybe_face.result   # Unpack the face coordinates
    face_image = image[y:y+h, x:x+w] # Crop the image. Eyes are only on faces
  else:
    return Maybe(False, 'No face detected.')

  maybe_distance = determine_distance(maybe_face) #Get face-camera distance
  if maybe_distance.success:
    distance = maybe_distance.result
  else:
    return maybe_distance

  maybe_tilt = find_head_tilt(face_image)  #Get lateral tilt of the head
  if maybe_tilt.success:
    tilt = maybe_tilt.result
  else:
    tilt = 0 # If error just ignore it and set to '0' for our purposes

  return Maybe(True, {'distance' : distance, 'tilt' : tilt})


def detect_face(MaybeImage):
  """
  Take an image and return positional information for the largest face in it.

  Args:
      MaybeImage: An image grabbed from the local camera.

  Returns:
      Maybe tuple((bool, [int]) or (bool, str)): True and list of positional
      coordinates of the largest face found. False and an error string if no
      faces are found.
  """

  if MaybeImage.success:
    image = MaybeImage.result
  else:
    return MaybeImage

  faceCascade = cv2.CascadeClassifier(config.face_cascade_path) # Load face classifier

  major_ver = (cv2.__version__).split('.')[0]

  if int(major_ver) < 3:
    flag_for_detect = cv2.cv.CV_HAAR_SCALE_IMAGE
  else:
    flag_for_detect = cv2.CASCADE_SCALE_IMAGE

  # Detect faces in the image
  # faces will be an iterable object
  faces = faceCascade.detectMultiScale(
      image=image,
      scaleFactor=1.1,
      minNeighbors=5,
      minSize=(40, 40),
      flags = flag_for_detect
  )

  try:                                     # Assume largest face is the subject
    face = faces[0]                        # [0] index is largest face.
    return Maybe(True, face)
  except IndexError:
    return Maybe(False, "No faces detected. This may be due to low or uneven \
lighting.")


def find_head_tilt(face):
  """Take one facial image and return the angle (only magnitude) of its tilt"""
  classifier = cv2.CascadeClassifier(config.eye_cascade_path)

  if classifier.empty():
    return Maybe(False, "Empty classifier")

  eyes = classifier.detectMultiScale(face)

  # If at least two eyes have been identified, use them to determine the
  # lateral angle of the head. If one or none are detected, skip this. If
  # more are detected, assume any after the first two are false positives.
  if len(eyes) > 1:
    left  = eyes[0]
    right = eyes[1]
    print 'Left eye', left, 'Right eye', right
    slope = (left[1] - right[1]) / (left[0] - right[0])
    angle = abs(atan(slope))

    if config.text_mode:
      print('Eyes detected, indicating a lateral inclination of {}'
              .format(angle))

    return Maybe(True, angle)

  return Maybe(False, "No eyes found")


def detect_slouching(MaybePos):
  """
  Use provide postural information to determine if the subject is slouching.

  Args:
      MaybePos Maybe(bool, [float, float]: Head distance and lateral tilt.

  Returns:
      Maybe(bool, dict) or Maybe(bool, str): The determination of slouching
      or an error message from somewhere upstream.
      dict will contain booleans for 'body_slouching', and 'head_tilting'
  """
  if MaybePos.success:
    posture = MaybePos.result
  else:
    return MaybePos

  current_posture = posture.get('distance')
  tilt            = posture.get('tilt')

  c_min = config.distance_reference * (1.0 - config.thoracolumbar_tolerance)
  c_max = config.distance_reference * (1.0 + config.thoracolumbar_tolerance)

  if config.text_mode:
    print('    Measured distance: {}'.format(current_posture))
    print('    Should be within {} and {}'.format(c_min, c_max))

  if c_min <= current_posture <= c_max:
    body_slouching = False
  else:
    body_slouching = True

  # TODO: Adjust so these two types of slouching alert users with different messages.
  if tilt > config.cervical_tolerance:
    head_tilting = True
  else:
    head_tilting = False

  print("body_slouching:", body_slouching)
  print("head_tilting:", head_tilting)
  return Maybe(True, {'body_slouching' : body_slouching, 'head_tilting' : head_tilting})

# MaybeSlouching
def slouching_results():
  maybe_image     = take_picture(config.video_device)
  maybe_posture   = determine_posture(maybe_image)
  maybe_slouching = detect_slouching(maybe_posture)

  return maybe_slouching

if __name__ == '__main__':
  slouching_results()