Ok, lets see if I can explain myself like a lil child. I upload a picture to 4 Images. I then go into the admin control and use the auto thumbnail feature. When I am done, I then go to the front page. The thumbnail image that is shown is of very poor quality. Like the photo has been exposed to light before before being processed in a dark room. The picture is not what it should be in looks. Some of the pictures turn out pink, some turn out purple, some are a mixture of the 2 colors. Some pictures come out very light, some pictures come out to dark. Some picture are half good and some are half bad. When I say half bad I mean that, lets for for arguement sake take a picture and fold it in half. The top half is perfect, nothing wrong with it. The bottom half can have anything wrong with it from one of the problems above( when above I mean like pink,purple,to dark or light ).
I use GD Conversion tool for thumbnails.