最近用fastadmin开发了一个项目，需要用到视频的封面图片，客户又不能一一提供视频对应的封面，为减少工作量，需要在后台上传视频后直接生成默认封面图片，也可以自动上传想要的封面图片；
利用fastadmin框架，生成视频上传功能，在此基础上添加功能。
首先是页面，放的是add页面，edit页面是一样的
此处是手动上传的封面图
<div class="form-group">
<label class="control-label col-xs-12 col-sm-2">{:__('Head_image')}:</label>
<div class="col-xs-12 col-sm-8">
<div class="input-group">
<input id="c-head_image" class="form-control" size="50" name="row[head_image]" type="text">
<div class="input-group-addon no-border no-padding">
<span><button type="button" id="plupload-head_image" class="btn btn-danger plupload" data-input-id="c-head_image" data-mimetype="image/gif,image/jpeg,image/png,image/jpg,image/bmp" data-multiple="false" data-preview-id="p-head_image"><i class="fa fa-upload"></i> {:__('Upload')}</button></span>
<span><button type="button" id="fachoose-head_image" class="btn btn-primary fachoose" data-input-id="c-head_image" data-mimetype="image/*" data-multiple="false"><i class="fa fa-list"></i> {:__('Choose')}</button></span>
</div>
<span class="msg-box n-right" for="c-head_image"></span>
</div>
<ul class="row list-inline plupload-preview" id="p-head_image"></ul>
</div>
<div class="col-sm-10 col-sm-offset-2 col-xs-12" style="color: red;">封面图272*272，小于50kb</div>
</div>
此处是上传视频
<div class="form-group">
<label class="control-label col-xs-12 col-sm-2">{:__('Video_file')}:</label>
<div class="col-xs-12 col-sm-8">
<div class="input-group">
<input id="c-video_file" class="form-control" size="5000" name="row[video_file]" type="text">
<div class="input-group-addon no-border no-padding">
<span><button type="button" id="plupload-video_file" class="btn btn-danger plupload" data-mimetype="video/mp4" data-input-id="c-video_file" data-multiple="false" data-preview-id="p-video_file"><i class="fa fa-upload"></i> {:__('Upload')}</button></span>
</div>
<span class="msg-box n-right" for="c-video_file"></span>
</div>
<!--<ul class="row list-inline plupload-preview" id="p-video_file"></ul>-->
<video id="video" style="width: 160px;height:120px; " ></video>
</div>
<div class="col-sm-10 col-sm-offset-2 col-xs-12" style="color: red;">时长不超过15s，mp4格式，小于1M</div>
</div>
此处是上传视频后自动生成的默认封面图
<div class="form-group">
<label class="control-label col-xs-12 col-sm-2">{:__('默认封面图')}:</label>
<div class="col-xs-12 col-sm-8">
<input id="fengmianinput" class="form-control" type="hidden" name="row[moren_image]">
<img style="width: 160px;height:120px; " id="fengmian" src="" alt="">
</div>
<div class="col-sm-10 col-sm-offset-2 col-xs-12" style="color: red;">上传视频后自动生成</div>
</div>
这一部分只要根据平时框架自动生成就可以了，最主要的是js文件中添加方法，下面放上最主要的js部分代码
//add方法内添加
add: function () {
$("#plupload-video_file").data('upload-success',function(res){
//视频上传成功后触发
//console.log(res);
$("#video").attr('src',res.url);
});
var video = document.getElementById('video');
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
width = video.clientWidth;
height = video.clientHeight;
video.addEventListener('loadeddata', function (e) {
// console.log('loadeddata')
this.currentTime=1.5;
canvas.width = this.videoWidth;
canvas.height = this.videoHeight;
width = this.videoWidth;
height = this.videoHeight;
// console.log(width, height)
// console.log(this)
var currentTime = this.currentTime;
var that=this;
setTimeout(function(){
//此处的setTimeout方法，是为了防止截取到视频前几帧为黑屏，如果可以确保视频没有黑屏，可以不用setTimeout方法
ctx.drawImage(that, 0, 0, width, height);
var src = canvas.toDataURL('image/jpeg');
console.log(src);
$("#fengmianinput").attr('value',src);
$("#fengmian").attr('src',src);
},200);
});
Controller.api.bindevent();
},
//edit方法同理
edit: function () {
$("#plupload-video_file").data('upload-success',function(res){
//console.log(res);
$("#video").attr('src',res.url);
});
var video = document.getElementById('video');
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
width = video.clientWidth;
height = video.clientHeight;
video.addEventListener('loadeddata', function (e) {
// console.log('loadeddata')
this.currentTime=1.5;
canvas.width = this.videoWidth;
canvas.height = this.videoHeight;
width = this.videoWidth;
height = this.videoHeight;
// console.log(width, height)
// console.log(this)
var currentTime = this.currentTime;
var that=this;
setTimeout(function(){
ctx.drawImage(that, 0, 0, width, height);
var src = canvas.toDataURL('image/jpeg');
console.log(src);
$("#fengmianinput").attr('value',src);
$("#fengmian").attr('src',src);
},200);
});
Controller.api.bindevent();
},
需要注意的是，这里的默认封面图（上传视频自动截取的图），图片编码是base64，数据库需要用longtext类型。
在使用框架生成视频上传功能后，不要忘记设置可以上传的视频类型以及大小。