前端判断ios图片是否旋转，需要在页面中引用exif.js

    <script type="text/javascript" src="js/exif.js" ></script> 

在vue中使用

  npm install exif.js
   import EXIF from 'exif-js'
  // 挂载到vue实例中
  Vue.prototype.Exif = EXIF

 // 通过base64来判断图片大小
function getImgSize(base64url) {
  //获取base64图片大小，返回KB数字
  var str = base64url.replace('data:image/jpeg;base64,', '');//这里根据自己上传图片的格式进行相应修改
  var strLength = str.length;
  var fileLength = parseInt(strLength - (strLength / 8) * 2)
  // 由字节转换为KB
  var size = (fileLength / 1024).toFixed(2)
  return parseInt(size)
}

// 生成base64图片
export function base64 (selector, targetSize = 3956) {
  return new Promise(resolve => {
    var oFReader = new FileReader()
    var file = document.getElementById(selector).files[0]
    let size = file.size / 1024, Orientation = null
    EXIF.getData(file, function(){
      Orientation = EXIF.getTag(this, 'Orientation');
    })
    loading = weui.loading()
    oFReader.readAsDataURL(file)
    oFReader.onloadend = function(oFRevent){
      if (size <= targetSize) {
        resolve(oFRevent.target.result)
        loading.hide()
      } else {
        var img = new Image()
        img.src = oFRevent.target.result
        if (img.complete) {
          callback()
        } else {
          img.onload = callback
        }
        function callback() {
          resolve(compressImg(img, Orientation, targetSize))
          img = null
        }
      }
    }
  })
}

// 压缩图片
function compressImg (img, Orientation, targetSize) {
  let canvas = document.createElement("canvas")
  let ctx = canvas.getContext('2d')
  let width = img.width
  let height = img.height
  //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
  let ratio;
  if ((ratio = width * height / 3500000) > 1) {
    ratio = Math.sqrt(ratio)
    width /= ratio
    height /= ratio
  } else {
    ratio = 1
  }
  canvas.width = width;
  canvas.height = height;
  //铺底色
  ctx.fillStyle = "#fff";
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  if (Orientation == 3) {
    canvas.width = width;
    canvas.height = height;
    ctx.rotate(Math.PI);
    ctx.drawImage(img, 0, 0, -width, -height)
  } else if (Orientation == 8) {
      canvas.width = height;
      canvas.height = width;
      ctx.rotate(Math.PI * 3 / 2);
      ctx.drawImage(img, 0, 0, -width, height)
  } else if (Orientation == 6) {
      canvas.width = height;
      canvas.height = width;
      ctx.rotate(Math.PI / 2);
      ctx.drawImage(img, 0, 0, width, -height)
  } else {
      canvas.width = width;
      canvas.height = height;
      ctx.drawImage(img, 0, 0, width, height)
  }
  // 循环压缩至100k左右
  let quality = 1.05, ndata = ''
  do {
    quality -= 0.05
    ndata = canvas.toDataURL('image/jpeg', quality)
  } while (getImgSize(ndata) > targetSize)
  loading.hide()
  return ndata
}

使用示例：

// dom
 <input id="inputCamera" @change="cameraImg" type="file" accept="image/*" capture="camera" />

//js 
   base64('inputCamera1').then(res => {
        console.log(res)
    })