Cache/copy Bitmaps loaded from external source?

Question

I'm working on a chat application that retreives user profile icons from remote sources (e.g. Blogger, Yahoo, Gravatar, etc). Easy to get the images in a Loader and display them.
The problem is that a single thread could have hundreds of records, but probably only 10-20 active commenters. In a standard browser, each <img...> link after the first one is cached, so you only hit the source site once. Is there any way to cache/store/copy those images within Flash to avoid requesting the same image over and over?
I can do it in the Local sandbox by accessing the BitmapData of the loader content and cloning a new bitmap for subsequent instances of the same request URL, but of course once the application moves to the Internet the security system requires a Policy file allowing bitmap access. I doubt that I can get Yahoo to add one for me. I don't need to manipulate the bitmap at all, just copy it. Or reference it as content from multiple Sprites, or something along that line. Once I've downloaded the image once, I don't see why the security system would prevent me from displaying it unchanged as many times on the page as needed.
If this can't be done in AS3, perhaps it would be a good feature to add in the next release? Remote image caching is pretty well accepted in other platforms.

Answer 1

I put  trace on the image URLs, and they always showed HTTP Status = 200 - they were loading every time. In any case, I came up with an easy workaround. I out a php script on my hosting server that fetches the image, then use that as the URL for the loader object. Voila, no security violation because the php is in the same domain as the swf. Cut down load time by at least a factor of 5.
Only problem is, the loader always gets a 200 status on the php script, eve though I'm setting an Http header to send a 404 (the same URL from a browser gets the 404 response.) That generates an Unkown File Type error in my SWF so I have to trap that rather than the http status. It works, except I can't differentiate b/t a non-existant image and a server or connecion error. Or at least, I can't do it without a lot more code