<img src="./suica.jpg" alt="suica.jpg" />

#+ATTR_HTML: :alt おいしそうなすいか
[[file:./suica.jpg]]

#+CAPTION: おいしそうなすいか
#+ATTR_HTML: :alt おいしそうなすいか
[[file:./suica.jpg]]

(defun org-altcaption--get-caption (paragraph info)
  "段落に設定されているキャプション文字列を取得する。

org-html-paragraph関数内の「;; Standalone image.」の部分より。"
  (if paragraph
      (let ((raw (org-export-data (org-export-get-caption paragraph) info)))
        (if (org-string-nw-p raw) raw nil))))

(defun org-altcaption--get-link-parent (link info)
"linkの親要素を取得する。ただし、linkが最初のリンクでない場合はnil。

org-html-link関数内より。"
  ;; Extract caption from parent's paragraph.  HACK: Only
  ;; do this for the first link in parent (inner image link
  ;; for inline images).  This is needed as long as
  ;; attributes cannot be set on a per link basis.
  (let* ((parent (org-export-get-parent-element link))
         (link (let ((container (org-export-get-parent link)))
                 (if (and (eq 'link (org-element-type container))
                          (org-html-inline-image-p link info))
                     container
                   link))))
    (and (eq link (org-element-map parent 'link #'identity info t))
         parent)))

(defvar org-altcaption--link nil)

(defun org-altcaption--org-html-link (old-func link desc info)
  "org-html-linkに対するaround advice"
  ;; Pass link to org-altcaption--org-html--format-image function
  (let ((org-altcaption--link link))
    (funcall old-func link desc info)))

(defun org-altcaption--org-html--format-image (old-func source attributes info)
  "org-html--format-imageに対するaround advice"
  ;; Add alt attribute if link has caption
  (if (and org-altcaption--link (null (plist-get attributes :alt)))
      (let ((caption (org-altcaption--get-caption (org-altcaption--get-link-parent org-altcaption--link info) info)))
        (when caption
          (setq attributes (plist-put attributes :alt caption))
          ;;(message "caption=%s" caption)
          )))
  ;; Call original function
  (funcall old-func source attributes info))


(defun org-altcaption-activate ()
  (interactive)
  (advice-add #'org-html-link :around #'org-altcaption--org-html-link)
  (advice-add #'org-html--format-image :around #'org-altcaption--org-html--format-image))

(defun org-altcaption-deactivate ()
  (interactive)
  (advice-remove #'org-html-link #'org-altcaption--org-html-link)
  (advice-remove #'org-html--format-image #'org-altcaption--org-html--format-image))

#+ATTR_HTML: :target _blank
山といえば [[https://www.pref.yamanashi.jp/][山梨県]] と [[http://www.pref.shizuoka.jp/index.html][静岡県]] 。富士山にまたがるこの二つの県は……

#+ATTR_HTML: :target _blank
山といえば [[https://www.pref.yamanashi.jp/][山梨県]] と
#+ATTR_HTML: :target _blank
[[http://www.pref.shizuoka.jp/index.html][静岡県]] 。富士山にまたがるこの二つの県は……

(defcustom org-limit-image-size '(0.99 . 0.5) "Maximum image size") ;; integer or float or (width-int-or-float . height-int-or-float)

(defun org-limit-image-size--get-limit-size (width-p)
  (let ((limit-size (if (numberp org-limit-image-size)
                        org-limit-image-size
                      (if width-p (car org-limit-image-size)
                        (cdr org-limit-image-size)))))
    (if (floatp limit-size)
        (ceiling (* limit-size (if width-p (frame-text-width) (frame-text-height))))
      limit-size)))

(defvar org-limit-image-size--in-org-display-inline-images nil)

(defun org-limit-image-size--create-image
    (old-func file-or-data &optional type data-p &rest props)

  (if (and org-limit-image-size--in-org-display-inline-images
           org-limit-image-size
           (null type)
           ;;(image-type-available-p 'imagemagick) ;;Emacs27 support scaling by default?
           (null (plist-get props :width)))
      ;; limit to maximum size
      (apply
       old-func
       file-or-data
       (if (image-type-available-p 'imagemagick) 'imagemagick)
       data-p
       (plist-put
        (plist-put
         (org-plist-delete props :width) ;;remove (:width nil)
         :max-width (org-limit-image-size--get-limit-size t))
        :max-height (org-limit-image-size--get-limit-size nil)))

    ;; default
    (apply old-func file-or-data type data-p props)))

(defun org-limit-image-size--org-display-inline-images (old-func &rest args)
  (let ((org-limit-image-size--in-org-display-inline-images t))
    (apply old-func args)))

(defun org-limit-image-size-activate ()
  (interactive)
  (advice-add #'create-image :around #'org-limit-image-size--create-image)
  (advice-add #'org-display-inline-images :around #'org-limit-image-size--org-display-inline-images))

(defun org-limit-image-size-deactivate ()
  (interactive)
  (advice-remove #'create-image #'org-limit-image-size--create-image)
  (advice-remove #'org-display-inline-images #'org-limit-image-size--org-display-inline-images))

(defvar org-flyimage-in-activate-links nil)

(defun org-flyimage-activate-links (old-func limit)
  (let ((org-flyimage-in-activate-links t))
    (funcall old-func limit)))

(defun org-flyimage-remove-inline-images-in (beg end)
  ;; is faster to use (overlays-in beg end) ?
  (loop for ov in org-inline-image-overlays
        if (let ((ovbeg (overlay-start ov))
                 (ovend (overlay-end ov)))
             (and (numberp ovbeg) (numberp ovend)
                  (< ovbeg end) (> ovend beg)))
        do (org-display-inline-remove-overlay ov t nil nil)))

(defun org-flyimage-remove-flyspell-overlays-in (old-func beg end)
  (funcall old-func beg end)

  (if t ;;(not org-flyimage-in-activate-links) ;;in t, reflect #+attr_html: :width immediately. but slow
      (org-flyimage-remove-inline-images-in beg end))

  (if org-flyimage-in-activate-links
      (org-display-inline-images nil t beg end)))

(defun org-flyimage-activate ()
  (interactive)
  (advice-add #'org-activate-links :around #'org-flyimage-activate-links)
  (advice-add #'org-remove-flyspell-overlays-in :around #'org-flyimage-remove-flyspell-overlays-in))

(defun org-flyimage-deactivate ()
  (interactive)
  (advice-remove #'org-activate-links #'org-flyimage-activate-links)
  (advice-remove #'org-remove-flyspell-overlays-in #'org-flyimage-remove-flyspell-overlays-in))

;; org.elより
(defun org-activate-links (limit)
  "Add link properties to links.
This includes angle, plain, and bracket links."
  (catch :exit
    (while (re-search-forward org-link-any-re limit t)
      (let* ((start (match-beginning 0))
             (end (match-end 0))
             (visible-start (or (match-beginning 3) (match-beginning 2)))
             (visible-end (or (match-end 3) (match-end 2)))
             (style (cond ((eq ?< (char-after start)) 'angle)
                          ((eq ?\[ (char-after (1+ start))) 'bracket)
                          (t 'plain))))
        (when (and (memq style org-highlight-links)
                   ;; Do not span over paragraph boundaries.
                   (not (string-match-p org-element-paragraph-separate
                                        (match-string 0)))
                   ;; Do not confuse plain links with tags.
                   (not (and (eq style 'plain)
                             (let ((face (get-text-property
                                          (max (1- start) (point-min)) 'face)))
                               (if (consp face) (memq 'org-tag face)
                                 (eq 'org-tag face))))))
          (let* ((link-object (save-excursion
                                (goto-char start)
                                (save-match-data (org-element-link-parser))))
                 (link (org-element-property :raw-link link-object))
                 (type (org-element-property :type link-object))
                 (path (org-element-property :path link-object))
                 (properties            ;for link's visible part
                  (list
                   'face (pcase (org-link-get-parameter type :face)
                           ((and (pred functionp) face) (funcall face path))
                           ((and (pred facep) face) face)
                           ((and (pred consp) face) face) ;anonymous
                           (_ 'org-link))
                   'mouse-face (or (org-link-get-parameter type :mouse-face)
                                   'highlight)
                   'keymap (or (org-link-get-parameter type :keymap)
                               org-mouse-map)
                   'help-echo (pcase (org-link-get-parameter type :help-echo)
                                ((and (pred stringp) echo) echo)
                                ((and (pred functionp) echo) echo)
                                (_ (concat "LINK: " link)))
                   'htmlize-link (pcase (org-link-get-parameter type
                                                                :htmlize-link)
                                   ((and (pred functionp) f) (funcall f))
                                   (_ `(:uri ,link)))
                   'font-lock-multiline t)))
            (org-remove-flyspell-overlays-in start end)
            (org-rear-nonsticky-at end)
            (if (not (eq 'bracket style))
                (add-text-properties start end properties)
              ;; Handle invisible parts in bracket links.
              (remove-text-properties start end '(invisible nil))
              (let ((hidden
                     (append `(invisible
                               ,(or (org-link-get-parameter type :display)
                                    'org-link))
                             properties)))
                (add-text-properties start visible-start hidden)
                (add-text-properties visible-start visible-end properties)
                (add-text-properties visible-end end hidden)
                (org-rear-nonsticky-at visible-start)
                (org-rear-nonsticky-at visible-end)))
            (let ((f (org-link-get-parameter type :activate-func)))
              (when (functionp f)
                (funcall f start end path (eq style 'bracket))))
            (throw :exit t)))))         ;signal success
    nil))