base64文件处理

base64 转换

• base64 转图片

  `data:${type};base64,`+code

  type 是文件类型，比如图片 image/png,image/jpeg,pdf:application/pdf

• base64 转为 Blob 对象

  function dataURLtoBlob(dataurl) {
      var arr = dataurl.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 });
  }
  let blob = dataURLtoBlob(`data:${mimetype};base64,`+image)`)

• blob 转为 File

   function blobToFile(theBlob, fileName){
     theBlob.lastModifiedDate = new Date();
     theBlob.name = fileName;
     return theBlob;
  }
  var file = blobToFile(blob, imgName);

• base64 转为 File 对象

   function dataURLtoFile(dataurl, filename) {//将base64转换为文件
       var arr = dataurl.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 File([u8arr], filename, {type:mime});
   }
  let file = dataURLtoFile(`data:${mimetype};base64,`+image)`,'PDF.pdf')

• 转为 url

  window.URL.createObjectURL(blob|file)

• 下载

  let a=document.getElementById('download');
   let blob=dataURLtoBlob(`data:${image[0].mimetype};base64,`+image[0].image);
   a.download = image[0].name+'.pdf';
   a.href = window.URL.createObjectURL(blob)