galetahub/simple-captcha — pull request #23 by praveenggg (2012-07-31 10:48:09+00:00)
Title: Update lib/simple_captcha/image.rb

I am using Ruby 1.9.3 and Rails 3.2.3, i used your gem but captcha image is not displaying,its giving error
StandardError (Error while running convert: convert: unrecognized gravity type `'Center'' @ convert.c/ConvertImageCommand/1508.
): and then i realised 'center' in line no. 67 causing this error.so i making this change.