The Facebook Sharer will not show a share image if the image is kind of large - this ruby function requests to share a URL programmatically so when a real users attempts to share the image will appear.

preload_facebook_share_img.rb

require 'rest-client'

def clear_url(url)
  cookie = "" # Load facebook and copy and paste your session detail in here

  cookie = Hash[ cookie.split('; ').map { |line| line.split('=') } ]

  resp = RestClient.get "https://www.facebook.com/sharer/sharer.php?u=#{url}", { cookies: cookie }

  raise 'whoops' if resp.code != 200
  sleep 5 # Not sure how fast we can go - no complaints at one request per 5 seconds
end