at the moment its hardcoded at the top of GD.php - protected $quality = 75; The next release - 2.2.3 has a method called set_default_quailty(xx); which you can define a global quality for image quality but for now the easiest way would to be just tweak that value in GD.php
Thank you very much for the speed
I'm dealing with this issue as well. Where do I find the gd.php file? thanks!