Jack Kamm <jackkamm@gmail.com> writes:

> I've attached a patch which implements displaying remote images.
>
>> This is a longstanding problem, and there was an attempt to patch it in
>> 2014, but the patch was never accepted:
>> https://lists.gnu.org/archive/html/emacs-orgmode/2014-11/msg00583.html
>
> Compared to the previous attempt from 2014, I think my patch is simpler
> -- it doesn't require creating any temp files.
>
>> The fault might be with image.el rather than with org-mode itself --
>> for example, when I execute the following elisp, I get the same blank
>> box:
>
> After doing some reading, I learned that image.el doesn't really create
> the image. Instead, create-image simply creates a blank string with a
> text property pointing to the image file location, and the rendering of
> the image gets handled later by the C code (for example, png_load_body()
> in image.c), which doesn't know how to read remote image files.
>
> Since I wasn't comfortable trying to get the C code to read the remote
> file, I instead took the approach used by image-mode.el, which reads the
> remote image file and passes its contents directly to create-image,
> instead of just passing the filename.
>
> From 47120666dad6eb0b6ca716325d7de86924e1d28e Mon Sep 17 00:00:00 2001
> From: Jack Kamm <jackkamm@gmail.com>
> Date: Thu, 28 Nov 2019 17:45:56 -0800
> Subject: [PATCH] org: display remote images
>
> ---
>  lisp/org.el | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/lisp/org.el b/lisp/org.el
> index 90f222c8b..dc7bcc7aa 100644
> --- a/lisp/org.el
> +++ b/lisp/org.el
> @@ -16754,13 +16754,20 @@ buffer boundaries with possible narrowing."
>                           (t nil)))
>                         (old (get-char-property-and-overlay
>                               (org-element-property :begin link)
> -                             'org-image-overlay)))
> +                             'org-image-overlay))
> +                       (remote-p (file-remote-p file)))
>                     (if (and (car-safe old) refresh)
>                         (image-refresh (overlay-get (cdr old) 'display))
> -                     (let ((image (create-image file
> +                     (let ((image (create-image (if (not remote-p)
> +                                                    file
> +                                                  (with-temp-buffer
> +                                                    (insert-file-contents file)
> +                                                    (string-make-unibyte
> +                                                     (buffer-substring-no-properties
> +                                                      (point-min) (point-max)))))
>                                                  (and (image-type-available-p 'imagemagick)
>                                                       width 'imagemagick)
> -                                                nil
> +                                                remote-p
>                                                  :width width)))
>                         (when image
>                           (let ((ov (make-overlay

FWIW, looks good to me, but I've only (carefully) read the patch: I have not actually ran it.

--
Nick

"There are only two hard problems in computer science: cache
invalidation, naming things, and off-by-one errors." -Martin Fowler