If your Drupal 6 Status report page returns the following error:
GD Image Rotation Low Quality / Poor Performance
The installed version of PHP GD does not support ...
or your Drupal 7 Status report page reports:
GD library rotate and desaturate effects 2.0 or higher
The GD Library for PHP is enabled, but was compiled without support for functions used by the rotate and desaturate effects. It was probably compiled using the official GD libraries from http://www.libgd.org instead of the GD library bundled with PHP. You should recompile PHP --with-gd using the bundled GD library. See the PHP manual.
This error occurs because PHP is missing the GD graphics library or it is not compiled just right. Not all operating systems (platforms) install it as part of PHP.
Select your operating system below for instructions on how to correct this (or see CentOS instructions).