canvas - How to post a large image to user's Facebook timeline -

i building site lets users browse 3d images. have added facebook share button. button works, shares url , small thumbnail (the thumbnail works sometimes).

is possible create button shares large custom image, in same way upload photo own timeline?

i cannot use meta tags, because images change through javascript. cannot let facebook find image automatically, because rendered in canvas 3d viewer on webpage.

thanks in advance!