<template>
 <div>
  <input type="file" id="upload" accept="image" @change="upload" />
 </div>
</template>
<script>
export default {
 data() {
  return {
   picValue:{},
   headerImage:''
  };
 },
 components: {},
 methods: {
  upload(e) {
   console.log(e);
   let files = e.target.files || e.dataTransfer.files;
   if (!files.length) return;
   this.picValue = files[0];
   this.imgPreview(this.picValue);
  },
  imgPreview(file) {
   let self = this;
   let Orientation;
   //去獲取拍照時(shí)的信息，解決拍出來的照片旋轉(zhuǎn)問題
   self.Exif.getData(file, function() {
    Orientation = self.Exif.getTag(this, 'Orientation');
   });
   // 看支持不支持FileReader
   if (!file || !window.FileReader) return;

   if (/^image/.test(file.type)) {
    // 創(chuàng)建一個(gè)reader
    let reader = new FileReader();
    // 將圖片2將轉(zhuǎn)成 base64 格式
    reader.readAsDataURL(file);
    // 讀取成功后的回調(diào)
    reader.onloadend = function() {
     let result = this.result;
     let img = new Image();
     img.src = result;
     //判斷圖片是否大于100K,是就直接上傳，反之壓縮圖片
     if (this.result.length <= 100 * 1024) {
      self.headerImage = this.result;
      self.postImg();
     } else {
      img.onload = function() {
       let data = self.compress(img, Orientation);
       self.headerImage = data;
       self.postImg();
      };
     }
    };
   }
  },
  compress(img, Orientation) {
   let canvas = document.createElement('canvas');
   let ctx = canvas.getContext('2d');
   //瓦片canvas
   let tCanvas = document.createElement('canvas');
   let tctx = tCanvas.getContext('2d');
   let initSize = img.src.length;
   let width = img.width;
   let height = img.height;
   //如果圖片大于四百萬像素，計(jì)算壓縮比并將大小壓至400萬以下
   let ratio;
   if ((ratio = (width * height) / 4000000) > 1) {
    console.log('大于400萬像素');
    ratio = Math.sqrt(ratio);
    width /= ratio;
    height /= ratio;
   } else {
    ratio = 1;
   }
   canvas.width = width;
   canvas.height = height;
   //    鋪底色
   ctx.fillStyle = '#fff';
   ctx.fillRect(0, 0, canvas.width, canvas.height);
   //如果圖片像素大于100萬則使用瓦片繪制
   let count;
   if ((count = (width * height) / 1000000) > 1) {
    console.log('超過100W像素');
    count = ~~(Math.sqrt(count) + 1); //計(jì)算要分成多少塊瓦片
    //      計(jì)算每塊瓦片的寬和高
    let nw = ~~(width / count);
    let nh = ~~(height / count);
    tCanvas.width = nw;
    tCanvas.height = nh;
    for (let i = 0; i < count; i++) {
     for (let j = 0; j < count; j++) {
      tctx.drawImage(
       img,
       i * nw * ratio,
       j * nh * ratio,
       nw * ratio,
       nh * ratio,
       0,
       0,
       nw,
       nh
      );
      ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
     }
    }
   } else {
    ctx.drawImage(img, 0, 0, width, height);
   }
   //修復(fù)ios上傳圖片的時(shí)候 被旋轉(zhuǎn)的問題
   if (Orientation != '' && Orientation != 1) {
    switch (Orientation) {
     case 6: //需要順時(shí)針（向左）90度旋轉(zhuǎn)
      this.rotateImg(img, 'left', canvas);
      break;
     case 8: //需要逆時(shí)針（向右）90度旋轉(zhuǎn)
      this.rotateImg(img, 'right', canvas);
      break;
     case 3: //需要180度旋轉(zhuǎn)
      this.rotateImg(img, 'right', canvas); //轉(zhuǎn)兩次
      this.rotateImg(img, 'right', canvas);
      break;
    }
   }
   //進(jìn)行最小壓縮
   let ndata = canvas.toDataURL('image/jpeg', 0.1);
   tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
   return ndata;
  },
  rotateImg(img, direction, canvas) {
   //最小與最大旋轉(zhuǎn)方向，圖片旋轉(zhuǎn)4次后回到原方向
   const min_step = 0;
   const max_step = 3;
   if (img == null) return;
   //img的高度和寬度不能在img元素隱藏后獲取，否則會出錯(cuò)
   let height = img.height;
   let width = img.width;
   let step = 2;
   if (step == null) {
    step = min_step;
   }
   if (direction == 'right') {
    step++;
    //旋轉(zhuǎn)到原位置，即超過最大值
    step > max_step && (step = min_step);
   } else {
    step--;
    step < min_step && (step = max_step);
   }
   //旋轉(zhuǎn)角度以弧度值為參數(shù)
   let degree = (step * 90 * Math.PI) / 180;
   let ctx = canvas.getContext('2d');
   switch (step) {
    case 0:
     canvas.width = width;
     canvas.height = height;
     ctx.drawImage(img, 0, 0);
     break;
    case 1:
     canvas.width = height;
     canvas.height = width;
     ctx.rotate(degree);
     ctx.drawImage(img, 0, -height);
     break;
    case 2:
     canvas.width = width;
     canvas.height = height;
     ctx.rotate(degree);
     ctx.drawImage(img, -width, -height);
     break;
    case 3:
     canvas.width = height;
     canvas.height = width;
     ctx.rotate(degree);
     ctx.drawImage(img, -width, 0);
     break;
   }
  },
  postImg() {
   //這里寫接口
　　　　//打印的圖片base64

   console.log('this.headerImage',this.headerImage);
   //接口 axios
  }
 }
};
</script>

npm install exif-js --save

import Exif from 'exif-js'
Vue.use(Exif)
Vue.prototype.Exif = Exif