实现功能：
（1）能够打开和保存图片。
（2）能够实现绘画图形（直线、空心（实心）椭圆、空心（实心）矩形、多边形）；多边形主要包括三角形、四边形、五边形、六边形。
（3）实现画笔粗细的变更；
（4）实现画笔颜色的变更；
　　（5）能够用鼠标在绘图板上单击拖动进行随笔画；
（6）具有橡皮擦除功能以及全屏清除功能。(Realization function:

(1) can open and save the picture.

(2) can realize drawing graphics (straight line, hollow (Shi Xin) ellipse, hollow (Shi Xin) rectangle, polygon); polygons mainly include triangles, quadrangles, pentagons, hexagons.

(3) to change the thickness of the brush.

(4) to change the color of the brush.

(5) you can use the mouse to drag and move the sketches on the drawing board.

(6) rubber erase function and full screen scavenging function.)