I. Introduction
Two typical representations for images are raster graphics and vector graphics. Raster graphics is a grid of pixels, with each pixel storing either a color/grey value or an index into a color palette. Pixel based image representation has revealed its drawbacks in many applications such as image magnification and printing. Vector graphics defines images using graphics objects like curves and surfaces, rather than discrete points of pixels. The vector representation is scalable, compact and resolution independent. It facilitates many image editing processes, for example, object-based image editing [1]. In recent years the research of exploring graphics based image representations and converting images from raster graphics into vector graphics has attracted increasing interest [2]–[12].