Background Color of Inline Image for Orgmode in Dark Theme

Displaying inline image in orgmode is useful. But when emacs theme is dark theme and the image has transparent background, the image is difficult to view.

To fix this problem, we can define an advice to filter the image from org--create-inline-image.

(defun org--create-inline-image-advice (img)
  (nconc img (list :background "#f8f8f8")))
(advice-add 'org--create-inline-image
            :filter-return #'org--create-inline-image-advice)

org--create-inline-image-advice adds :background to the image. #f8f8f8 is the light white color I used for light theme.

:filter-return is the where argument for advice-add, this means the advice function is applied to the result of the original function:

(lambda (&rest r) (funcall advice-function (apply oldfun r)))

With the advice, the transparent background inline image looks the same no matter light or dark theme.