carvr is a application that implements image resizing through seam carving. It is optimized for speed and has a very minimal interface.
This application stemmed from a desire to revive some of my old computer vision classwork. Seam carving is a simple algorithm, but optimizing for speed is an interesting challenge. This implementation is careful about recalculating image energy, only doing so for patches where the image has been modified.
carvr is hosted on GitHub, where you can find more details about the implementation and how to build / install it on your own machine.