JS实现预加载视频音频/视频获取截图（返回canvas截图）

/** * Create by Capricorncd 2017 */// 同域资源实现视频截图，可上传的图片数据格式// 非同域资源实现canvas截图预览// 提示码const CODES = { 0: 'success', 1: 'The url is not valid', 2: 'onerror'}/** * constructor * @param opts.url 音频|视频URL * @param opts.type 'audio|video' * @param opts.callback 回调函数 */function loadMedia(opts) { this.callback = opts.callback || function (res) {  console.log(res); } // 初始化 this.init(opts);}// prototypeloadMedia.prototype = { /**  * 初始化media  * @param url  */ init: function (opts) {  let self = this;  if (!opts.url || typeof opts.url !== 'string') {   this.callback({code: 1, msg: CODES[1]});   return;  }  // 创建media  let mediaType = opts.type === 'audio' ? 'audio' : 'video';  this.media = document.createElement(mediaType);  console.log('this.media', this.media);  // loaded  this.listener('canplaythrough', function (e) {   // 截图   if (mediaType === 'video') {    self.screenshot();   } else {    self.callback({     code: 0,     msg: CODES[0],     thumb: null,     media: this.media,     canvas: null    });   }  });  // error  this.listener('error', function (e) {   self.callback({code: 2, msg: CODES[2], data: e});  })  this.media.setAttribute('src', opts.url); }, screenshot: function () {  // create canvas  let canvas = document.createElement('canvas');    canvas.width = this.media.videoWidth;    canvas.height = this.media.videoHeight;  let ctx = canvas.getContext('2d');  // 截取  ctx.drawImage(this.media, 0, 0);  let thumb = null;  // 非跨域资源  // !!非同域资源无法获取数据  try {   let type = 'image/png';   let data = canvas.toDataURL(type);   thumb = this.toBlobData(data, type);  } catch (e) {}  this.callback({   code: 0,   msg: CODES[0],   thumb: thumb,   media: this.media,   canvas: canvas  }) }, // 数据转换 toBlobData: function (data, type) {  // 获取base64数据  // base64数据格式:  // "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAkGB+wgHBgkIBwgKCgkLDRYPDQw//9k="  data = window.atob(data.split(',')[1]);  let ia = new Uint8Array(data.length);  for (let i = 0; i < data.length; i++) {   ia[i] = data.charCodeAt(i);  };  // canvas.toDataURL 返回的默认格式是 image/png  return new Blob([ia], {type: type}); }, /**  * addEventListener 事件监听  * @param en EventName  * @param callback  */ listener: function (en, callback) {  this.media.addEventListener(en, function (e) {   if (callback) {    callback(e);   } else {    console.warn(this);   }  }, false); } /**  * 资源是否跨域  * @param url 资源地址  * @returns {boolean}  */ // isCrossDomain: function (url) { //  let loc, host, protocol; //  loc = window.location; //  host = loc.host; //  protocol = loc.protocol; //  // 是否为http链接 //  if (/(http|https)://///.test(url)) { //   if (url.indexOf(protocol + '//' + host) >= 0) { //    return false; //   } else { //    return true; //   } //  } //  // './xxx.mp4' '/xxx.mp4' 'xxx.mp4' //  return false; // }}

// 参考资料// HTML5的Video标签的属性,方法和事件汇总// http://www.cnblogs.com/TF12138/p/4448108.html# 使用import loadMedia from '@/common/js/load-media'let loadVideo = new loadMedia({ type: 'video', url: 'http://xmqvip1-1253933147.file.myqcloud.com/chat/video/60/2017/09/29/qgj1c8K7oaYn-SCVideo-Merged.mp4', callback: handleCallback})function handleCallback (res) {    console.log(res)    // canplaythrough    if (res.code === 0) {    }    // error    if (res.code === 2) {    }   }