Hi,

attached is a patch that should fix a bug in the function
org-mime-org-buffer-htmlize (thanks to punchagan on irc!).

When exporting an org buffer with a latex snippet including the org
option tex: dvipng the images were always created in /tmp/ltxpng/, but
the reported link in the htmlized buffer was the local ./ltxpng folder;
so, unless the org file to htmlize was actually in /tmp, the user got an
error saying that the image could not be found.

This was caused by the two different ways in which the function
org-mime-replace-images is used inside of org-mime-org-buffer-htmlize
and org-mime-htmlize.

To correct the problem, the function org-mime-replace-images doesn't
take anymore the current-file parameter (that was only used to get its
directory) and instead always creates a temporary directory using
temporary-file-directory.

Keep up the good work!
Carlo Nucera