title: error WriteBlob Failed using ImageMagick 6.7.9
body: <p>I want to create an image from a pdf file. I have installed ImageMagick on a Linux server
  and successfully created an image from a terminal with root access. </p>
  
  <p><strong>Command:</strong>    </p>
  
  <pre><code> /usr/local/bin/convert http://www.artisticancestry.com/sites/default/files/media/Getting%20Started_7.pdf /public_html/testing.png
  </code></pre>
  
  <p>But When i am going to execute this command from php exec() function. It is showing this type of error</p>
  
  <p><strong>error:</strong>
       convert: unable to open image <code>/public_html/testing-0.png': No such file or directory @ error/blob.c/OpenBlob/2642.
       convert: WriteBlob Failed</code>/public_html/testing-0.png' @ error/png.c/MagickPNGErrorHandler/1751.</p>
  
  <p>There is some permission issue but don't know which file has no permission.How can I find out what is causing this problem and how can I solve it?</p>