Ruby png Manipulation

Nice, short ruby script I came across showing basic png usage (albeit with a twisted mutator ;)). [disclaimer] This may not work with ruby-1.9

[sourcecode language="ruby"]
require 'rubygems'
require 'png'

def f(x,y)
((x^y) & ((y-350) >> 3 )) ** 2
end

canvas = PNG::Canvas.new(500.500)

0.upto(499) do |y|
0.upto(499) do |x|
if ((f(x,y) >> 12) & 1) == 1
canvas[x,499-y] = PNG::Color::Black
else
canvas[x,499-y] = PNG::Color::White
end
end
end

png = PNG.new(canvas)
png.save 'ruby.png'
[/sourcecode]