The first step in working towards Friendly Bot is to get some code working that can capture an image from a webcam and detect a face in it. I knew that OpenCV had facilities for doing facial recognition, but I was hoping to avoid some of the documentation pain that I have heard about from other people. I did a quick search for rubygems that wrapped opencv and found spyglass by André Medeiros.

Spyglass makes a serious attempt to simplify the OpenCV API and so far it looks very promising. There is even a great example of doing facial recognition that got me started almost immediately.


Before I could install spyglass I needed to install OpenCV.

$ brew install opencv

The OpenCV classifier needs an xml document that tells it what features to look for. Luckily a bunch of examples come installed with OpenCV.

$ ls /usr/local/Cellar/opencv/


Now I installed spyglass and made one slight adaptation to the example provided in the gem.

require 'bundler/setup'
require 'spyglass'
require './lib/face_picker'

include Spyglass 

classifier  ="./haarcascade_frontalface_default.xml")
window      = "Video"
cap         = 0
frame       =

loop do
  cap >> frame

  rects = classifier.detect(frame, scale_factor: 1.5, min_size:, 30))
  rect = rects.sort_by(&:area).last # pick the biggest face found
  frame.draw_rectangle(rect,, 0, 0)) if rect

  break if GUI::wait_key(100) > 0

Basically I wanted to avoid having multiple faces in the image so I did a quick “pick the biggest one” and drew a box around it in the frame.

Wait, is it seriously that easy?


Friendly Bot Milestones

  1. Write some code that can detect a face in an image
  2. Write some artoo code that can control a servo
  3. Make a webcam mount with servos for pan and tilt
  4. Write some artoo code that controls the roomba
  5. Load code onto the Beagle Bone Black that controls the roomba and servos
  6. Load code onto the Beagle Bone Black that can detect faces seen by the webcam
  7. Write some glue code on the Beagle Bone Black that turns the roomba and servos to keep a face in the center of the image
  8. Make the roomba wander until it finds a face to follow (first time we can use the title Friendly Bot)
  9. Make friendly bot play the “curious” beeps when it finds a face
  10. Make Friendly Bot recognize family members and do “happy” or “skeptical” beeps