png
About
png is a pure-ruby PNG library. It lets you write a PNG without any C libraries. Of course it is “slow”.
Installing png
Just install the gem:
$ sudo gem install png
Using png
require 'png'
canvas = PNG::Canvas.new 200, 200
# Set a point to a color
canvas[100, 100] = PNG::Color::Black
# draw an anti-aliased line
canvas.line 50, 50, 100, 50, PNG::Color::Blue
png = PNG.new canvas
png.save 'blah.png'