执行本实例后，用鼠标拖动选中的小图片进行拼接，可以拼成一幅完整的图片。本实例的知识点有：鼠标事件的监听，Graphics类和Image类的应用。-After the implementation of this instance, use the mouse to drag the selected image stitching can be taped together to form a complete picture. Knowledge in this instance: the mouse event listener, Graphics, and Image class.