base64 encode/decode

gistfile1.txt

$ file test.png 
test.png: PNG image data, 22 x 13, 16-bit grayscale, non-interlaced
$ md5sum test.png 
c6db60c696981f908324d3365e0836c0  test.png

# base64 encoding with ruby 1.8.7
$ irb-ruby-1.8.7-p334
ruby-1.8.7-p334 :001 > RUBY_VERSION
 => "1.8.7" 
ruby-1.8.7-p334 :002 > b64 = [File.read('test.png')].pack('m')
 => "iVBORw0KGgoAAAANSUhEUgAAABYAAAANEAAAAADYXh38AAAAAmJLR0T//xSr\nMc0AAAAJcEhZcwAAAEgAAABIAEbJaz4AAADMSURBVCjPY/hPAmD4/z88HL8S\nhDxQMQMDAfPg8gyRkQwM5ubvVOPjlZVlZHx8Hj4ECU+eLCsrKdnR8f8/RP73\nbyST4+J27PgHBJs2WVuDhDk4nj179crDA81kCIeHhwEKWFlBwvb2QUGrVn37\nhlUxF9fnzyDunz/PnoHo37937UpIsLDAovjv35CQwsJfv/7+bWiIjAQJa2h8\n+vTkCRcXRPHfv3DFhoYqKi9Nw8OlpGRkgoPfvAEJd3RISsrITJ0KYoPk4R4k\nKVIGg2IAI+rURZux+/IAAAAldEVYdGRhdGU6Y3JlYXRlADIwMTEtMTAtMjhU\nMTk6Mjg6NTErMDk6MDBtp1cwAAAAJXRFWHRkYXRlOm1vZGlmeQAyMDExLTEw\nLTI4VDE5OjI4OjUxKzA5OjAwHPrvjAAAAAp0RVh0bGFiZWwAdGVzdLvYsQ4A\nAAASdEVYdGxhYmVsOnBvaW50c2l6ZQAxMtFMvRcAAAAASUVORK5CYII=\n" 
ruby-1.8.7-p334 :003 > File.open('test.txt', 'w+'){|f| f.write(b64)}
 => 606 

$ irb-ruby-1.8.7-p334
ruby-1.8.7-p334 :001 > RUBY_VERSION
 => "1.8.7" 
ruby-1.8.7-p334 :002 > require 'digest/md5' 
 => true 
ruby-1.8.7-p334 :003 > Digest::MD5.hexdigest(File.read('test.txt').unpack('m').first)
 => "c6db60c696981f908324d3365e0836c0" 
ruby-1.8.7-p334 :004 > Digest::MD5.hexdigest(File.read('test.png'))
 => "c6db60c696981f908324d3365e0836c0" 

$ irb-ruby-1.9.2-p290 
ruby-1.9.2-p290 :001 > RUBY_VERSION
 => "1.9.2" 
ruby-1.9.2-p290 :002 > require 'digest/md5' 
 => true 
ruby-1.9.2-p290 :003 > Digest::MD5.hexdigest(File.read('test.txt').unpack('m').first)
 => "c6db60c696981f908324d3365e0836c0" 
ruby-1.9.2-p290 :004 > Digest::MD5.hexdigest(File.read('test.png'))
 => "c6db60c696981f908324d3365e0836c0"