Imagemagick

 The version of Imagemagick on velvet did not support the -path option for mogrify

# mogrify
Version: ImageMagick 6.2.4 07/28/09 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2005 ImageMagick Studio LLC

Upgraded using:

How to install ImageMagick and Imagick on Debian Linux 
Also needed:

• http://stackoverflow.com/questions/11515118/imagemagick-not-converting-jpegs
• http://www.hardwaretutorials.com/2012/05/installing-png-support-for-debian/

Result:

/usr/local/bin/mogrify | more
Version: ImageMagick 6.8.1-0 2012-12-20 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2013 ImageMagick Studio LLC