This is excellent, Ryan; thanks! This is exactly what I was talking about in my second reply here.
Though I’m having trouble adapting it to the photo card protocol, which will be my primary use of this feature. I suppose it would be easy enough to put all of your code except the Twitter:image line in my themes header, but use one of the meta plugins to customize that line as I post.
Which brings me to my next question for you: If I leave all of this in my theme’s header, can I “override” the values by using one of the aforementioned plugins in an individual post?
For example, can I make the Twitter:image line point to a default image (such as a logo), but use the HiFi plugin (at the posting level) to point it to a different image? Will the latter override the former, or will it cause a conflict?
Thanks for your help, it’s much appreciated!