Ariel Shamir and Shai Avidan have presented "Seam carving". This new algorithm allows an image to be resized non-uniformly. So, you can change the height and width of an image independantly, but the main properties of an image remain undistorted.
The algorithm detects parts of the image with least information, like a blue sky and other almost equal colored parts. When resizing an image, the pixels in these areas are stretched or removed, leaving the rest of the image untouched. Areas of an image that absolutely need to be preserved can be manually excluded, and the seam generating function will negotiate paths around those pixels.
This technique can also be used to remove whole portions of an image without noticable artifacts. You could cut a person or object out of photographs and the image will be distorted in an unnoticable way to fill the gap. Watch the video to see it in action.
http://www.faculty.idc.ac.il/arik/imret.pdf
