OpenCV: Show what camera sees, capture if anything other than 'q' is pressed

camera.rb

require 'rubygems'
require 'opencv'

include OpenCV

camera = CvCapture.open(1)

window = GUI::Window.new("camera")

while true
  camera.grab
  window.show(img = camera.retrieve)
  key = GUI.wait_key(33)
  if key == 'q'.ord
    break
  else
    open('foo.jpg', 'wb') do |f|
      f.write img.encode('.jpg').pack("c*")
    end
  end
end

$ brew install opencv # or equivalent on other platforms
$ gem install opencv