- content_for :additional_meta do
  meta name="twitter:card" content="photo"
  meta name="twitter:image" content=@content.file.url
img src=@content.file.url

- content_for :additional_meta do
  meta name="twitter:card" content="photo"
  meta name="twitter:image" content="#{root_url}#{@content.file.url}"
img src=@content.file.url

Use full path for twitter cards URL
Use full path for twitter cards URL

osak/Sakura,osak/Sakura,osak/Sakura