potrace

potrace is a utility for tracing a bitmap, which means, transforming a bitmap into a smooth, scalable image. The input is a portable bitmap (PBM), and the default output is an encapsulated PostScript file (EPS). A typical use is to create EPS files from scanned data, such as company or university logos, handwritten notes, etc. The resulting image is not "jaggy" like a bitmap, but smooth, and it can be scaled to any resolution.