Good news for every one that uses Gbarcode, and those thinking of using it, I created a small wrapper module that is more Ruby-ish and also uses Cairo to print out to PNG. The functionality is bare-bones, with a fixed height of 150 pixels and width is determined by the length of the encoded barcode. It works well for Code 128 barcodes. Grab the ruby file here.
To use this module, here is an example (note that bad encoding schemes will result in a raised excpetion, hence the begin/rescue block):
b = GBC::Barcode.new(ARGV, Gbarcode::BARCODE_ANY)
puts b.ascii, b.partial, b.encoding
b = Markaby::Builder.new()
img(:src => "out.png")
f = File.open("out.html","w")
rescue Exception => e