img_src_data.rb

#http://tools.ietf.org/html/rfc2397
img_path = '...pictures/img.jpg'
img = File.open(img_path, 'rb').read
img_type = case img[0..10]
  when /^GIF8/
    'gif'
  when Regexp.new('^\x89PNG', nil, 'n')
    'png'
  when Regexp.new('^\xff\xd8\xff\xe0\x00\x10JFIF', nil, 'n'), Regexp.new('^\xff\xd8\xff\xe1(.*){2}Exif', nil, 'n')
   'jpeg'
else 'unknown'
end
data64 = [img].pack('m0')

html = %(<img alt="" src="data:image/#{img_type};base64,#{data64}" />)