Kirupa -Photo Gallery. resizing it to fit

I have many photos, I want to create a photo gallery. I used Kirupa photo gallery but its not that good, when I load a big picture in the default sized box, it does not show the hole picture but a part of it that fits, the rest goes in the mask.

What I want, is when I press a button, the rektangel that will load the image resize it self to fit the image and loads it up image after image. I have seen this thing used in sites.

simliar to this.
http://www.dirklambrechts.com/

Just simple but, resizes it self to the image, and loads it preloader. :frowning:
I also have this client who wants like that, I need helpt.

Thank you very much.