export const compressImage=function (files,fn,preCallbackFn,i) {

    let newfile = files.files[0];

    let quality = 0.1;

    const name = newfile.name; //文件名

    let reader = new FileReader();

    reader.readAsDataURL(newfile);

    reader.onload = (e) => {

        const src = e.target.result;

        const img = new Image();

        img.src = src;

        img.onload = (e) => {

            const w = img.width;

            const h = img.height;

            //生成canvas

            const canvas = document.createElement('canvas');

            const ctx = canvas.getContext('2d');

            // 创建属性节点

            const anw = document.createAttribute("width");

            anw.nodeValue = w;

            const anh = document.createAttribute("height");

            anh.nodeValue = h;

            canvas.setAttributeNode(anw);

            canvas.setAttributeNode(anh);

            //铺底色 PNG转JPEG时透明区域会变黑色

            ctx.fillStyle = "#fff";

            ctx.fillRect(0, 0, w, h);

            ctx.drawImage(img, 0, 0, w, h);

            // quality值越小，所绘制出的图像越模糊

            const base64 = canvas.toDataURL('image/jpeg', quality); //图片格式jpeg或webp可以选0-1质量区间

            console.log(`原图${(src.length / 1024).toFixed(2)}kb`, `新图${(base64.length / 1024).toFixed(2)}kb`);

            if(base64.length>1024*1024*1){

                return false;

            }

            let arr = base64.split(','), mime = arr[0].match(/:(.*?);/)[1],

                bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);

            while(n--){

                u8arr[n] = bstr.charCodeAt(n);

            }

            let obj = new Blob([u8arr], {type:'image/jpeg'});

            preCallbackFn && preCallbackFn(base64,obj,i);

            fn && fn(obj);

        }

    }

};

//上传图片校验

export const checkImg=function(file){

    var aa=file.value.toLowerCase().split('.');

    if(!(aa[aa.length-1]=='gif'||aa[aa.length-1]=='jpg'||aa[aa.length-1]=='jpeg'||aa[aa.length-1]=='png')){

        throw {code:400,msg:"请选择格式为*.jpg、*.gif、*.jpeg、*.png的图片"};

    }

    var imagSize =  file.files[0].size;

    if(imagSize>1024*1024*1){

        throw {code:401,msg:"图片过大，无法上传"};

    }

    return true;

};

import {checkImg,compressImage} from "com";

 imgPreview(){

          let file=document.getElementById("imgInput");

          try {

              checkImg(file)

          }catch(e) {

              if(e.code==401){

                  if(compressImage(file,this.upImg,this.preCallbackFn) === false){

                      return  alert(e.msg);

                  }

                  return true;

              }else {

                  return  alert(e.msg);

              }

          }

          if (file.files && file.files[0]) {

              let reader = new FileReader();

              reader.onload = function (evt) {

                  let img = document.querySelector('#img_preview img');

                  img.setAttribute('src', evt.target.result);

              }

              reader.readAsDataURL(file.files[0]);

              this.upImg(file.files[0]);

          }

      },

upImg(file){
      let formData = new FormData();
      formData.append("img", file,"image.jpeg");

　　　　//fileUpload 上传为接口

      fileUpload(formData).then(data=>{

          if(!data) return false;
          userModifyImg(data).then(data=>{
              if(!data) return false;
              alert("上传图片成功！")
          });
      });
  },