Added check for facebook_image post meta as primary Facebook thumbnail

[ddn]

On some sites, maintainers may desire to retain more control of what image is used for Facebook OpenGraph thumbnails.

My site, for example, uses a wide landscape format for site images. When Facebook pulls these images, it often crops them in an unfavorable way. I prefer to manually select the image I want promoted for the site content.

This change checks for a facebook_image post_meta value, and if it exists, returns it as the SOLE thumbnail for opengraph. Removing the return true would allow it to be returned as one of many if there are other thumbnails available.

Ideally, this would probably be an option that can be chosen in the setting.

[jdevalk]

Hi @ddn,

thanks for this! We're going to be far more active here on Github so we're actually looking properly into all these requests now. To be honest, we'll probably never add a "technical" fix like this. I want to do something like this but it'd require an actual interface in the plugin, where in the social meta box people could select an image... If you want to build a patch for that, that'd be most welcome :) if not, do let me know and I'll write up the issue and I'll assign it to a dev.

[barrykooij]

I'm not expecting a new PR on this here, so I've created an issue #784.