通过picasa api上传图片时如何防止jpeg压缩?

我用的是巨蟒 client library 对于PicasaWebAlbumsAPI,可以将一些jpeg图像上载到相册。但上传后照片看起来压缩得很厉害。在Picasa3.6中,有一个选项可以在不进行任何压缩的情况下以原始质量上载图像,但是在API中是否有类似的选项可以使用?

这是我用来创建照片并将其插入相册的一些代码:

upload_photo = gdata.photos.PhotoEntry()
upload_photo.summary = atom.Summary(text=title)
upload_photo.title = atom.Title(text=file_name)
upload_photo.text = atom.Text(text='Test')
upload_photo.author = atom.Author(atom.Name(text='Test Author'))
upload_photo.timestamp = gdata.photos.Timestamp(text='%i' % 
  int(time.mktime(photo_date.timetuple()) * 1000))
upload_photo.geo = gdata.geo.Where()
upload_photo.geo.Point = gdata.geo.Point()
upload_photo.geo.Point.pos = gdata.geo.Pos(text='%f %f' % (lat, lon))

imgContent = StringIO.StringIO(urlfetch.fetch('http://url.com/image1.jpg').content)

gpclient.InsertPhoto(album_or_uri=album_url, photo=upload_photo,   
  filename_or_handle=imgContent, content_type='image/jpeg')