一个简单的图形绘制程序,里面包含了圆,矩形,直线等矢量图形的绘制保存,里面还包含图形的操作,如拖动,旋转等.-Rendering a simple procedure, which contains a circular, rectangular, straight-line drawing vector graphics, such as preservation, which also includes a graphics operation, such as dragging, rota