Topic: images look better in SimpleViewer

After I re-created one of my older html/javascript thumbnail galleries using SimpleViewer2, I compared the two and noticed an interesting side benefit: the images looked better in the SimpleViewer gallery--even though I used the same files, copied from my older gallery.

Does SV do some kind of image-optimizing as the galley is created? If so, what does it do? I am using the script that operates within Photoshop. Not really a complaint, but curiosity. I also may have to keep this change in mind as I create my original files.