@vincent3569
> But If we use images of the gallery in a news (by using ZP plugin of TinyMCE), there is no <meta> data about these pictures. There are only <meta> data about news itself.
Yes, of course not because the current "page" or "item" is the news article and not the image(s) within. That's how FB & Co work, they use the current url (and ofcourse the info within the opengraph elements if available or often just the first image found). The plugin does not and cannot know about images statically embedded into an articlce or page or what you would like.
If you want to share images with their own url on these services, you need to share the actual image page.
@lainyrache
Yes, that is a way if you need to use another page. You can still use the html_meta_tags plugin for all other pages but you need to disable its description field to not get a double one. And of course you need to do this manual part on any page then, too.