The Study on GDI/GDI+ Rendering Function Defects and How to Avoid Them

This paper discusses some defects in GDI/GDI+ rendering functions in VC6/2003/2005/2008 of Windows XP/Vista/7. One type of defect is GDI´s drawing line functions, such as LineTo and PolyLine, which are always missing one pixel at the end point. Another type of bug is GDI´s drawing/filling rectangle/ellipse functions and filling polygon function, i.e. Rectangle, Ellipse and FillRgn, which are always missing one row of pixels in lower edge and right edge. In GDI+, the defects in drawing line has been removed, but the defects in drawing/filling rectangle/ellipse/polygon still exist, only in different forms. All these defects have no effect for general visualization applications. But for some special application, such as rasterization of vector data or measurement of geometric shape, it may make result imprecise. So, computer science and advance programmers should know these defects. The paper gives test data and some methods to avoid these defects in application program.