Tells an Arduino to move some servos in order to center a webcam on someone's face.

SerialServoControl.pde

/*******************************************************
* SerialServoControl Sketch
* Written by Ryan Owens for SparkFun Electronics
* 7/15/11
* Tweaked by Josh VanderLinden for himself
* 9/21/11
*
* This sketch listens to serial commands and uses the data
* to set the position of two servos.
*
* Serial Command Structure:
*   u/k: tilt the camera up
*   d/j: tilt the camera down
*   h/r: pan the camera right
*   l: pan the camera left
*
* Hardware Setup
* Servos should be connected to pins 2 and 3 of the Arduino.
* 9V DC Power supply is recommended as USB can't always handle powering two
* servos
*/

#include <Servo.h>

Servo servoTilt, servoPan;

void setup(){
  // The Tilt servo is attached to pin 2.
  servoTilt.attach(2);
  // The Pan servo is attached to pin 3.
  servoPan.attach(3);

  // Initially put the servos both at 90 degrees.
  servoTilt.write(90);
  servoPan.write(90);

  // Set up a serial connection for 57600 bps.
  Serial.begin(57600);
}

void loop() {
  short pos;

  switch (Serial.read()) {
    case 'u':
    case 'k':
      pos = servoTilt.read();
      if (pos > 0) servoTilt.write(pos - 1);
      break;
    case 'd':
    case 'j':
      pos = servoTilt.read();
      if (pos < 180) servoTilt.write(pos + 1);
      break;
    case 'l':
      pos = servoPan.read();
      if (pos > 0) servoPan.write(pos - 1);
      break;
    case 'r':
    case 'h':
      pos = servoPan.read();
      if (pos < 180) servoPan.write(pos + 1);
      break;
  }
}

smartcam.py

#!/usr/bin/env python

import cv
import serial
import time

class SmartCam(object):

    def __init__(self):
        self.capture = cv.CaptureFromCAM(4)
        self.cascade = cv.Load('haarcascade_frontalface_alt.xml')
        self.storage = cv.CreateMemStorage(0)
        self.port = '/dev/ttyACM0'
        self.baud = 57600
        self.timeout = 10
        self.size = None
        self._serial = None

        cv.NamedWindow("SmartCam", 1)

    def run(self):
        frame = cv.QueryFrame(self.capture)
        if self.size is None:
            self.size = cv.GetSize(frame)

        color_image = cv.CreateImage(self.size, 8, 3)

        while True:
            color_image = cv.QueryFrame(self.capture)

            # Smooth to get rid of false positives
            cv.Smooth(color_image, color_image, cv.CV_GAUSSIAN, 3, 0)

            faces = cv.HaarDetectObjects(color_image, self.cascade, self.storage, 1.2, 2, cv.CV_HAAR_DO_CANNY_PRUNING, (60, 60))

            if faces:
                (x, y, w, h), n = sorted(faces, key=lambda i: i[0][2] * i[0][3], reverse=True)[0]
                self.adjust_camera(x, y, w, h)
                #cv.Rectangle(color_image, (x, y), (x + w, y + h), 255)

            #cv.ShowImage("SmartCam", color_image)

            # Listen for ESC key
            c = cv.WaitKey(7) % 0x100
            if c == 27:
                break

    @property
    def half_height(self): return int(self.size[1] / 2.0)

    @property
    def half_width(self): return int(self.size[0] / 2.0)

    @property
    def window(self): return 20;

    @property
    def delay(self): return 0.005;

    def __del__(self):
        try:
            self._serial.close()
        except:
            pass

    @property
    def serial(self):
        if self._serial is None:
            self._serial = serial.Serial(self.port, self.baud, timeout=self.timeout)

        return self._serial

    def adjust_camera(self, x, y, w, h):
        """Attempts to center the camera on the biggest face"""

        mid_y = int(y + (h / 2.0))
        mid_x = int(x + (w / 2.0))

        if mid_y < (self.half_height - self.window):
            self.serial.write('u')
        elif mid_y > (self.half_height + self.window):
            self.serial.write('d')

        time.sleep(self.delay)

        if mid_x < (self.half_width - self.window):
            self.serial.write('l')
        elif mid_x > (self.half_width + self.window):
            self.serial.write('r')

        time.sleep(self.delay)

if __name__=="__main__":
    t = SmartCam()
    t.run()