title: convert:not authorized `aaaa` @ error/constitute.c/ReadImage/453
body: <p>I want to create a captcha pic by use <code>convert</code> from ImageMagick.</p>
  
  <p>And I follow <a href="http://www.grant-trebbin.com/2014/02/generating-captcha-from-linux-command.html" rel="noreferrer">this</a>, but there are some problem .</p>
  
  <p>Input In my linux shell:</p>
  
  <pre><code>convert -background white -fill black -font FreeSerif-Bold -pointsize 36 label:'adfgh' ./test.png
  </code></pre>
  
  <p>The Error is:</p>
  
  <blockquote>
    <p>convert:not authorized <code>adfgh</code> @ error/constitute.c/ReadImage/453.
    convert:missing an image filename <code>./test.png</code> @
    error/convert.c/ConvertImageCommand/3015</p>
  </blockquote>
  
  <p>My ImageMagick: Version:6.7.2-7 , I install it with <code>yum install ImageMagick</code> .</p>
  
  <p>I'm clueless. Any advice please?</p>