Gravity when cropping is needed.
?g=Center
?g=North
...
Files beign stored as converted_800x600_Center_GoldenGateBridge-001.jpg or converted_800x100_Center_GoldenGateBridge-001.jpg where first parameter is width and the second one is height.
http://localhost:3000/?w=800&h=100&g=Center&u=http://upload.wikimedia.org/wikipedia/commons/0/0c/GoldenGateBridge-001.jpg http://localhost:3000/?w=1024&h=768&g=Center&u=http://www.1920x1080wallpapers.com/images/photography-wallpapers/prokudin-gorskii-photography-art-image.jpg http://localhost:3000/?w=800&h=600&g=Center&u=http://www.handsonuniverse.org/get_images/images/20090802.ngc6992.HOS.jpg