Attaching images from the phone in org mode

config.el

(cl-defun iko/run-process-async (name program &key stdin args on-exit)
  "Run PROGRAM asynchronously with ARGS, outputting to BUFFER-NAME."
  (with-current-buffer (get-buffer-create (concat "*" name "*"))
    (let ((b (current-buffer))
          (p (apply #'start-process name (current-buffer) program args)))
      (set-process-sentinel
       p
       (lambda (proc event)
         (when (eq (process-status proc) 'exit)
           (when on-exit
             (funcall on-exit
                      (process-exit-status proc)
                      (with-current-buffer b (buffer-string))
                      proc
                      event))
           (kill-buffer b))))
      (when stdin
        (process-send-string p (if (string-suffix-p "\n" stdin)
                                   stdin
                                 (concat stdin "\n")))
        (process-send-eof p))
      p)))

(defun iko/scale-image-to-max-size (input-file output-file &optional max-width max-height)
  "Downscale INPUT-FILE to fit within MAX-WIDTH x MAX-HEIGHT (default 1280x720) and save as OUTPUT-FILE."
  (let ((max-width (or max-width 1280))
        (max-height (or max-height 720)))
    ;; Call ImageMagick 'convert' to resize while keeping aspect ratio
    (call-process
     "convert" nil nil nil
     input-file
     "-resize" (format "%dx%d>" max-width max-height)
     output-file)
    (message "Saved scaled image to %s" output-file)))


(defun iko/yad-select-img-from-dir (dir)
  "Use yad to select a file from DIR. Returns the selected file path."
  (let* ((command (s-join " "
                          `("yad"
                            "--file"
                            "--filter=\"Images | *.png *.jpg *.jpeg *.gif *.webp *.bmp\""
                            "--title=\"Select Image\""
                            "--add-preview"
                            "--large-preview"
                            ,(format "--workdir=%s" dir))))
         (output (string-trim (shell-command-to-string command))))
    (if (and (not (string-empty-p output))
             (file-exists-p output))
        output
      (user-error "No file selected or yad failed"))))

(defun iko/org-attach-image-from-phone ()
  (interactive)
  (let* ((attachDir ATTACHMENTS_CACHE_DIR)
         (user YOUR_USERNAME)
         (password YOUR_PASSWORD)
         (server YOUR_SERVER)
         (args
          `("-u" ,user
            "--path" ,NEXTCLOUD_FOLDER
            ,attachDir
            ,server)))
    (f-mkdir-full-path attachDir)
    (iko/run-process-async
     "nextcloudcmd-download"
     "nextcloudcmd"
     :args args
     :stdin password
     :on-exit
     (lambda (status-code _output _proc _event)
       (when (/= status-code 0)
         (user-error "nextcloudcmd failed with code %s" status-code))
       (let ((img-file (iko/yad-select-img-from-dir attachDir)))
         (message "selected %s" img-file)
         (when img-file
           (let ((tmpfile (make-temp-file "scaled-img-" nil ".png")))
             (message "buffer file: %s" tmpfile)
             (iko/scale-image-to-max-size img-file tmpfile)
             (org-download-image (concat "file://" tmpfile))
             (message "attached %s" img-file))))))))

See also https://valentin-herrmann.de/p/attaching-images-from-the-phone-in-org-mode/.