// 壓縮圖片 js

// eslint-disable-next-line no-unused-vars
export function compressImage (file, config) {
  // eslint-disable-next-line no-unused-vars
  let src
  // eslint-disable-next-line no-unused-vars
  let files
  // let fileSize = parseFloat(parseInt(file['size']) / 1024 / 1024).toFixed(2)
  const read = new FileReader()
  read.readAsDataURL(file)
  
 
return new Promise(function (resolve, reject) {
    read.onload = function (e) {
      let img = new Image()
      img.src = e.target.result
      img.onload = function () {
        // 預設按比例壓縮
        let w = config.width
        let h = config.height
        // 生成canvas
        let canvas = document.createElement('
 
canvas')
        let ctx = canvas.getContext('2d')
        let base64
        // 建立屬性節點
        canvas.setAttribute('width', w)
        canvas.setAttribute('height', h)
        ctx.drawImage(this, 0, 0, w, h)

        base64 = canvas.toDataURL(file['type'], config.quality)

        // 回撥函式返回file的值（將base64編碼轉成file）
        
 
// files = dataURLtoFile(base64) // 如果後臺接收型別為base64的話這一步可以省略

        // 回撥函式返回file的值（將base64轉為二進位制）
        let fileBinary = dataURLtoBlob(base64)

        resolve(fileBinary)
      }
    }
  })
};
　　// 將base64轉為二進位制
function dataURLtoBlob (dataurl) {
  let arr = dataurl.split(',')
  let mime = arr[0].match(/:(.*?);/)[1]
  let bstr = atob(arr[1])
  let n = bstr.length
  let u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new Blob([u8arr], { type: mime })
}

// base64轉碼（將base64編碼轉回file檔案）  此方法我沒用到
// eslint-disable-next-line no-unused-vars
function dataURLtoFile (dataurl) {
  let arr = dataurl.split(',')
  let mime = arr[0].match(/:(.*?);/)[1]
  let bstr = atob(arr[1])
  let n = bstr.length
  let u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new File([u8arr], { type: mime })
}

呼叫

　　　　　　let img = new Image(); //獲取轉成base64的圖片的寬高，用來設定壓縮過圖片的寬高
          img.src = file.content;
          img.onload = ()=>{
            that.ImgWidth = img.width; //獲取圖片的寬
            that.ImgHeight = img.height; //獲取圖片的高

            let biLi = that.ImgHeight/that.ImgWidth; //圖片的寬高比

            let config = {
              width: that.ImgWidth>375?375:that.ImgWidth,  //設定壓縮後圖片的款，大於手機寬度375時設定成375
              height: that.ImgWidth>375?(375*biLi):that.ImgHeight, //設定壓縮後圖片的高，通過寬高比來設定高
              quality: 0.8 
            }
            compressImage(file.file, config).then(result => { //壓縮呼叫  result 胃壓縮後的結果
              console.log('result')
              console.log(result)
              let newdate = new FormData()  轉成FormData格式，如有需要
              newdate.append('title', file.file.name);
              newdate.append('tags', 'brand_action_upload');    
              newdate.append('multipartFile', result);
              that.upImg(newdate,file.file.name)
            })
          }