Here is the prototype code which displaying image with text-property:

#+begin_src emacs-lisp
(put-text-property start end
                   'display (create-image thumbnail nil nil :ascent 'center :max-height thumbnail-size))
#+end_src

- If this is some kind of internal mechanism of Emacs, can someone explain why?

- If have some method to remove those horizontal lines. How to do it?

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