flickr extra=original_format

flickr api 有一點小變動，現在 getPublicPhotos 傳回來的 secret，原圖(original size)的 secret 不一樣。
1. 使用者必須是 pro 帳號
2. 使用者在 setting 裡面必須有開放原圖下載。
3. request 裡面必須加上 extras=original_format，api 除了本來的 secret 之外，會多回傳一個original_secret用來組成 original format 的 url。

<photo id="2564951972" owner="95212179@N00" secret="0c5792bbab" server="3112" farm="4" title="20080608(003)" ispublic="1" isfriend="0" isfamily="0" originalsecret="5e3a85a1da" originalformat="jpg"/>

Flickr Services
Note: Original photos behave a little differently. They have their own secret (called originalsecret in responses) and a variable file extension (called originalformat in responses). These values are returned via the API only when the caller has permission to view the original size (based on a user preference and various other criteria). The values are returned by the flickr.photos.getInfo method and by any method that returns a list of photos and allows an extras parameter (with a value of original_format), such as flickr.photos.search. The flickr.photos.getSizes method, as always, will return the full original URL where permissions allow.