JS预加载视频音频/视频获取截图技巧分享

/** * 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); } // prototype loadMedia.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) { } }