#load-media.js
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);
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,thumb: thumb,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;
// }
}
export default loadMedia;
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) {
}
}
总结
以上所述是小编给大家介绍的JS实现预加载视频音频/视频获取截图（返回canvas截图）。编程之家 jb51.cc 收集整理的教程希望能对你有所帮助，如果觉得编程之家不错，可分享给好友！感谢支持。
