重点是模仿了CAD的矢量绘图功能，实现了画直线，长方形，圆形、选择线条颜色，线条粗细、移动以及清除等操作，还可以保存。-The focus is an imitation of CAD vector graphics functions draw a straight line, rectangle, round, select the line color, line thickness, move and clear operation can also save.