图形学的课程设计，实现一个简单的绘图板，里面有填充、移动、旋转、放大、缩小等功能。运行时偶尔会有bug，请各位多提意见。-Graphics of the curriculum design, the realization of a simple drawing board, which has filled, move, rotate, enlarge, shrink and other functions. Run-time occasional bug, please do so.