I have played around with ImageMagic and GD2, this seems to me that ImageMagic generate more precise thumbnail. You may have a look at the Green Hill thumbnail comparing to others generated by GD2 at the following: http://totalcollection.info/ (http://totalcollection.info/), anyway this is not yet satisfied comparing to thumbnail created by, to name a few, Photoshop, ACDSee, irFan, etc.
I wonder how to increase the quality of thumbnail to not that blurry ones.
This is NOT a problem of GD2 and IM. Your pictures are scaled: Look here: http://forum.coppermine-gallery.net/index.php/topic,55038.0.html
Modify that:
http://forum.coppermine-gallery.net/index.php/topic,53320.msg265009.html#msg265009
After increasing the dimension, now it is crystal clear. But I wonder if this really slow the site?
http://totalcollection.info (http://totalcollection.info)