I've just uploaded the 2nd in what I hope will be a continuing series of 
articles about RMagick. This one is part 1 of a 2- (or more) parter 
about alpha compositing. You can read it here: 
http://rmagick.rubyforge.org/src_over.html

RMagick is an interface to the ImageMagick (http://www.imagemagick.org) 
and GraphicsMagick (http://www.graphicsmagick.org) image processing 
libraries. The RMagick home page is http://rmagick.rubyforge.org

If you have an idea for an article you'd like to see, shoot me an email 
at this address or at rmagick / rubyforge.org. Thanks!

Tim