Depixelizing Pixel Art (Sig 2011)

 http://research.microsoft.com/en-us/um/people/kopf/pixelart/

"Naïve upsampling of pixel art images leads to unsatisfactory results. Our algorithm extracts a smooth, resolution-independent vector representation from the image which is suitable for high-resolution display devices (Image © Nintendo Co., Ltd.)."

Nearest-neighbor result (Original: 40 x 16 pixels)

Algorithm result