How to lock Mac OS X screen

Go in applictions -> utilities and open 'Keychain Access'. In preferences check 'Show status in menu bar', then you will see a black padlock in the right of the task bar. To lock your screen you only need to click the padclock and select 'Lock Screen'. To lock require a password when your screen saver starts, go in 'System Preferences' -> 'Security', than check 'Require password to wake this computer from sleep or screensaver'. In Snow Leopard you can set the time when the screen will be blocked after the start of the screensaver.

References:

• In Mac OS X, how do I password-protect my computer? - http://kb.iu.edu/data/ajqx.html
• OS X Tip: Lock That Screen - http://www.whatdoiknow.org/archives/000957.shtml
• Add a screen locking icon to the menubar Desktop - http://www.macosxhints.com/article.php?story=20020901073230521

Install RMagic on Mac

This post documents the installation of RMagick on Snow Leopard. You need MacPorts installed. Install imagemagick library using MacPorts (have a cup of tea or coffe):

sudo port install tiff -macosx imagemagick +q8 +gs +wmf

Install rmagick gem (use sudo if you do not use rvm):

gem install rmagick

Now you should test if Ruby can use imagemagick:

irb -rubygems -r RMagick
ree-1.8.7-2010.01 > puts Magick::Long_version
This is RMagick 2.13.1 ($Date: 2009/12/20 02:33:33 $) Copyright (C) 2009 by Timothy P. Hunter
Built with ImageMagick 6.6.1-5 2010-05-16 Q8 http://www.imagemagick.org
Built for ruby 1.8.7
Web page: http://rmagick.rubyforge.org
Email: rmagick@rubyforge.org
=> nil
ree-1.8.7-2010.01 >

Done!

Thanks to: http://rmagick.rubyforge.org/install-osx.html