Ok i understood what it is doing.
Example:
I uploaded a .GIF File:
http://pimpandhost.com/index.php/image/show/id/147690
And it made him into: JPG:
http://pimpandhost.com/index.php/ima...42-medium.html
BUT If you notice, above the image there is
SMALL MEDIUM ORIGINAL
If you click on the "original"
You will still see "the .gif"
or in your case .png.
What we will do is
REMOVE File sizes from NON JPG Images.
So if you upload PNG or .GIF it simply WONT re size it and will keep your originals ONLY
