Alpha compositing with rmagick

Source

Destination

Result

Ruby source:

require 'rubygems'

require 'RMagick'

include Magick

dst = Image.read("dst.png")[0]

src = Image.read("src.png")[0]

result = dst.composite(src, 0, 0, OverCompositeOp)

result.write("result.png")

result.display

exit