vue在图片上传的时候压缩图片

需求：

上传到服务器的图片太大会导致服务器承受不了，故在前端传图片的时候将图片压缩后再传到服务器

直接上代码

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async getRealName(){
 
    let nickname = this.nickname.trim()
 
    let idnum = this.idnum.trim()
 
    let nameReg = /[\u4e00-\u9fa5]/gm
 
    let idnumReg = /^[a-z0-9]+$/i
 
    let zheng1 = document.getElementById("file1").files[0]
 
    let fan1 = document.getElementById("file2").files[0]
 
    if(nickname.length < 1) {
 
     return Toast('请输入姓名')
 
    }
 
    if(idnum.length < 1) {
 
     return Toast('请输入身份证号码')
 
    }
 
    if(!zheng1) {
 
     return Toast('请上传身份证信息页')
 
    }
 
    if(!fan1) {
 
     return Toast('请上传身份证国徽页')
 
    }
 
    if(zheng1.size/1024 > 1025) {
 
     this.imgCompress(zheng1,{quality:0.2},'zheng')
 
    }else {
 
     this.zheng = zheng1
 
    }
 
    if(fan1.size / 1024 > 1025) {
 
     this.imgCompress(fan1,{quality:0.2},'fan')
 
    }else {
 
     this.fan = fan1
 
    }
 
    setTimeout(()=>{
 
     let data = new FormData()
 
     data.append('nickname',nickname);//添加form表单中其他数据
 
     data.append('idnum',idnum)
 
     data.append('zheng',this.zheng,zheng1.name)
 
     data.append("fan",this.fan,fan1.name)
 
     let apiauth = localStorage.getItem('apiauth')
 
     let config = {
 
      headers:{'Content-Type':'multipart/form-data'},
 
      herders:{apiauth:apiauth}
 
     }
 
     axios.post("http://api139.ys11.ipfsico.com/index/index/realname",data,config).then((res)=>{
 
      Toast(res.data.msg)
 
      if(res.data.code == 1) {
 
       this.$router.replace({path:'/msite'})
 
      }
 
     })
 
    },1000)
 
   },
 
   //图片压缩
 
   imgCompress(path,obj,statu){
 
    let _this = this //这里的this 是把vue的实例对象指向改变为_this
 
    var img = new Image();
 
    if(statu == 'zheng') {
 
     img.src = _this.avatar1;
 
    }else {
 
     img.src = _this.avatar2
 
    }
 
    img.onload = function(){
 
     var that = this; //这里的this 是把img的对象指向改变为that 
 
     // 默认按比例压缩
 
     var w = that.width,
 
      h = that.height,
 
      scale = w / h;
 
     w = obj.width || w;
 
     h = obj.height || (w / scale);
 
     var quality = 0.7; // 默认图片质量为0.7
 
     //生成canvas
 
     var canvas = document.createElement('canvas');
 
     var ctx = canvas.getContext('2d');
 
     // 创建属性节点
 
     var anw = document.createAttribute("width");
 
     anw.nodeValue = w;
 
     var anh = document.createAttribute("height");
 
     anh.nodeValue = h;
 
     canvas.setAttributeNode(anw);
 
     canvas.setAttributeNode(anh);
 
     ctx.drawImage(that, 0, 0, w, h);
 
     // 图像质量
 
     if(obj.quality && obj.quality <= 1 && obj.quality > 0){
 
      quality = obj.quality;
 
     }
 
     // quality值越小，所绘制出的图像越模糊
 
     var base64 = canvas.toDataURL('image/jpeg', quality);
 
     // 回调函数返回base64的值
 
     var urlFile = _this.convertBase64UrlToBlob(base64) //这个地方的处理是为了把压缩的base64转化为对象，获得压缩后图片的大小size，方便对压缩后的图片再次进行判断；
 
     // console.log(urlFile)
 
     let file = _this.blobToFile(urlFile,path.name)
 
     console.log(file)
 
     if(statu == 'zheng') {
 
      _this.zheng = file
 
     }else {
 
      _this.fan = file
 
     }
 
     if(urlFile.size/1024 > 1025){
 
      Toast("图片过大，请重新上传图片")
 
     }
 
    }
 
   },
 
   convertBase64UrlToBlob(urlData){
 
    var arr = urlData.split(','), mime = arr[0].match(/:(.*?);/)[1],
 
     bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
 
    while(n--){
 
     u8arr[n] = bstr.charCodeAt(n);
 
    }
 
    return new Blob([u8arr], {type:mime});
 
   },
 
   blobToFile(theBlob, fileName){
 
    theBlob.lastModifiedDate = new Date();
 
    theBlob.name = fileName;
 
    return theBlob;
 
   },
 
   changeImage(e) {
 
    console.log(e.target.files)
 
    if(e.target.files[0]){
 
     this.ownImg = false
 
     var file = e.target.files[0];
 
     console.log(file)
 
     let filemaxsize = 4096
 
     let size = file.size / 1024
 
     if (size > filemaxsize){
 
      Toast('您上传的图片过大,请重新选择')
 
      this.disabled = true;
 
      this.formatImg = false
 
      return false
 
     }
 
     var name = file.name
 
     var fileTypes = [".jpg", ".png"];
 
     if(name) {
 
      var isNext = false;
 
      var fileEnd = name.substring(name.indexOf("."));
 
      for (var i = 0; i < fileTypes.length; i++) {
 
       if (fileTypes[i] == fileEnd) {
 
        console.log(fileTypes[i])
 
        isNext = true;
 
        this.disabled = false;
 
        this.formatImg = true;
 
        break;
 
       }
 
      }
 
      if (!isNext){
 
       Toast('暂不支持该类型图片');
 
       name = "";
 
       this.disabled = true;
 
       this.formatImg = false
 
       return false;
 
      }
 
     }
 
     var reader = new FileReader()
 
     var that = this
 
     var image = new Image()
 
     reader.readAsDataURL(file)
 
     reader.onload = function(e) {
 
      that.avatar1 = this.result
 
     }
 
    }
 
   },
 
   changeImg(event){
 
    var file = event.target.files[0]
 
    var name = file.name
 
    var fileTypes = [".jpg", ".png"];
 
    if(name) {
 
     var isNext = false;
 
     var fileEnd = name.substring(name.indexOf("."));
 
     for (var i = 0; i < fileTypes.length; i++) {
 
      if (fileTypes[i] == fileEnd) {
 
       console.log(fileTypes[i])
 
       isNext = true;
 
       this.disabled = false;
 
       this.formatImg = true;
 
       break;
 
      }
 
     }
 
     if (!isNext){
 
      Toast('暂不支持该类型图片');
 
      name = "";
 
      this.disabled = true;
 
      this.formatImg = false
 
      return false;
 
     }
 
    }
 
    var reader = new FileReader()
 
    var that = this
 
    reader.readAsDataURL(file)
 
    reader.onload = function(event) {
 
     that.avatar2 = this.result
 
    }
 
   }

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