How to use the relative link defined in markdown's frontmatter?

[kecrily]

I have now defined a relative link in the frontmatter of the md file named cover with the value of local image.

---
cover: ../assets/something.png
---

Now I want to use this as a value for <meta property="og:image" />, what should I do?

[kecrily]

See #82 and #123