blobToDataURL(blob, callback) {
    
    
        let a = new FileReader();
        a.onload = function (e) {
    
     callback(e.target.result); }
        a.readAsDataURL(blob);
      },

blobToFile (theBlob, fileName){
    
    
        theBlob.lastModifiedDate = new Date();
        theBlob.name = fileName;
        return theBlob;
      },

  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 });
      },