gif的播放与停止 https://www.zhangxinxu.com/wordpress/2015/12/css3-animation-js-canvas-gif-pause-stop-play/ canvas绘制gif https://blog.csdn.net/weixin_39394140/article/details/124143375 获取gif总帧数（原理） https://www.51cto.com/article/710042.html
