检索保存到Blobstore的照片的元数据

Question

我使用plupload将照片上传到Blobstore。该BlobInfo object有一些元数据

content_type: The content type of the blob. 
creation: The creation date of the blob, or when it was uploaded. 
filename: The file name that the user selected from their machine. 
size: The size of the uncompressed blob. 
md5_hash: The MD5 hash value of the uploaded blob. 

我的问题是怎样才能得到照片的其他元数据无论是从plupload或服务器端？具体来说，我需要检索一个“description”元数据字段。

Answer 1

我会用exif-py如下：

blob_reader = blobstore.BlobReader(blob_key) 
blob_reader_data = StringIO.StringIO(blob_reader.read()) 
tags = exifread.process_file(blob_reader_data) 

标签对象返回包含你正在寻找的元数据。