利用Qt实现一个电子画图板，能够画出基本的直线、曲线、椭圆，同时可以绘制基本图形，并且，可以实现对图形的颜色的填充，以及线条的颜色。-The realization of an electronic drawing board using Qt, to draw a straight line, curve, ellipse basic, also can draw the basic graphics, and can be implemented on graphics, fill colo