将图像转换为角度2中的base64

base64字符串的工作plunkr

https://plnkr.co/edit/PFfebmnqH0eQR9I92v0G?p=preview

  handleFileSelect(evt){      var files = evt.target.files;      var file = files[0];    if (files && file) {        var reader = new FileReader();        reader.onload =this._handleReaderLoaded.bind(this);        reader.readAsBinaryString(file);    }  }  _handleReaderLoaded(readerEvt) {     var binaryString = readerEvt.target.result; this.base64textString= btoa(binaryString); console.log(btoa(binaryString));    }