i have follow same error in my drupal site.
GD Image Filtering Low Quality / Poor Performance
The installed version of PHP GD does not support image filtering(desaturate, blur, negate, etc). 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 http://www.php.net/manual/en/image.setup.php. An implementation of imagefilter in PHP will be used in the interim.
GD Image Rotation Low Quality / Poor Performance
The installed version of PHP GD does not support image rotations. 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: http://www.php.net/manual/en/image.setup.php. An implementation of imagerotate in PHP will used in the interim.
I had change ";extion php_gd2.dll" to "extion php_gd2.dl"
The Package php5-gd is installed! But the error is not going!
I had read the same error on debian system http://drupal.org/node/465264
But how to in Centos5.3 (redhat 5)
CentOS Linux 5.3 MySQL v5.0.86 php 5.2.11
thanks!