So very strange issue. I only recently starting using auto loading in PHP 5.3+ and of course, this inevitably led to composer.
I did a really simple install with composer with only one package, php Image Workshop.
In addition to my own auto loader, I fire of the vendor/autoload.php
Then in my code:
use PHPImageWorkshop\ImageWorkshop;
$imagelayer = ImageWorkshop::initFromPath( $filename );
The namespace is valid and I get into the class which immediately throws an error.
PHP Fatal error: Call to undefined function PHPImageWorkshop\\imageCreateFromJPEG() in /var/www/html/vendor/sybio/image-workshop/src/PHPImageWorkshop/ImageWorkshop.php on line 55
imageCreateFromJPEG should be in the global namespace already, but the code in the class doesn't prefix it with a '\'.
Is this all right? I feel like I'm looking for a black cat in a dark room.
I guess the problem is GD is not available in your PHP instalation. Try to install php5-gd and it should work.
Good luck