Research And Implementation Of "Path" Generation And Anti-aliasing Rasterization Algorithms In OpenVG

OpenVG^TM is a royalty-free, cross-platform API that provides a low-level hardware acceleration interface for vector graphics libraries such as Flash and SVG. The targets of this paper is to implement high-quality 2D vector graphics for compelling user interfaces on small screen handheld devices while enabling hardware acceleration to provide fluidly interactive at very low power level.According to the defined rendering pipeline, this paper primarily targets at the "Path" related algorithms, and proposes the implementation algorithms of stroke/fill path generation, bezier path segment tessellation and trapezoid anti-aliasing rasterization in consistent with the design principle of OpenVG.This paper partitions the implementation of "Path" into three levels: path segment definition, segment type standardization, sub-path tessellation and rasterization. In the second level, all arc segments are transformed to cubic bezier segments. This paper introduces a new pipeline for stroke path generation and rasterization which take path segment as the rendering primitive. It introduces two structures named "Pen" and "Face" to solve the outline shape generation of a stroke path with any line width, and adds the end-cap style and line-join style to the shape. This paper implements bezier curve spline to polygon decomposition with the deCastlejau algorithm. To implement the two fill-rule defined in spec: "non-zero" and "even-odd", it proposes an efficient way with quick sorting and using horizontal scan line to generate trapezoid from arbitrary polygon , and at the same time finish the clipping within the screen surface.Trapezoid rasterization with antialiasing is the main emphasis of our research. This paper introduces a simple and efficient rasterizer with oblique scanning encoding procedure followed by a simplified two-step LUT combined with oriented filtering to implement rasterization with configurable anti-aliasing in OpenVG. After taking experiments on PPC, it shows that the performance can be improved more than 50% for comparison of the supper sampling with satisfying image quality and the table size is only about 10% of the Walter Algorithm.At last, this paper illustrate how OpenVG can be used in embed device with some applications like SVG player, scalable desktop, portable mapping etc, and again showed the significant meaning of the implementation of OpenVG.