Javascr ipt实现拖动,画线,画箭头,还有一个Js文件可以实现画椭圆等其它得多图形-Javascr ipt achieve Drive, line drawing, painting arrow, js document also a painting can be achieved much more elliptical and other graphics

用opengl实现bresenham算法画椭圆，先画1/4个椭圆，然后借助椭圆的对称性，画出其余部分-Use opengl achieve bresenham algorithm painted oval, first draw 1/4 oval, and then with the symmetry of the ellipse, and draw the rest of the

此功能实现在白板中画椭圆图形!类似Windows的画图模板(This function implementation drawing ellipse shapes in the whiteboard!)