Re-write org-include-img-from-pdf

- Use regular comment "# ()convertfrompdf:t" instead of using "#+HEADER" to mark
  file references that need to be converted. Ref:
  http://lists.gnu.org/archive/html/emacs-orgmode/2017-01/msg00260.html
- Update MWE and example output HTML
- Improve code
  - Use org-bracket-link-regexp
  - Add user-error if convert binary is not found
  - Optimize the let form
  - Improve org-include-img-from-pdf docstring

elisp/org-include-img-from-pdf/org-include-img-from-pdf-mwe.org

@@ -1,20 +1,18 @@
-#+TITLE: PDF Image
-#+NAME: fig:unicorn
-# Below HEADER is required where the pdf version of the referenced png file exists.
-#+HEADER: :convertfrompdf t
-# The below caption line is optional
-#+CAPTION: Org-mode Unicorn Logo
+# ()convertfrompdf:t # This is a special comment; tells that the upcoming
+                     # link points to a to-be-converted-to file.
+# If you have a foo.pdf that you need to convert to foo.png, mention the
+# to-be-converted-to name in the file link.
 [[./org-mode-unicorn-logo.png]]
 
 1. Save =org-include-img-from-pdf.el= to your =~/.emacs.d/elisp/org-include-img-from-pdf=.
 2. Add below to your emacs setup and evaluate it.
    #+BEGIN_SRC emacs-lisp
    (use-package org-include-img-from-pdf
-         :load-path "elisp/org-include-img-from-pdf"
-         :config
-         (progn
-           (with-eval-after-load 'ox
-             (add-hook 'org-export-before-processing-hook #'modi/org-include-img-from-pdf))))
+     :load-path "elisp/org-include-img-from-pdf"
+     :config
+     (progn
+       (with-eval-after-load 'ox
+         (add-hook 'org-export-before-processing-hook #'modi/org-include-img-from-pdf))))
    #+END_SRC
 3. Have =org-mode-unicorn-logo.pdf= file in the same directory as this one.
 4. Do =C-c C-e h o=.

elisp/org-include-img-from-pdf/org-include-img-from-pdf.el

@@ -1,49 +1,55 @@
-;; Time-stamp: <2016-09-09 11:10:20 kmodi>
+;; Time-stamp: <2017-04-04 23:03:47 kmodi>
 
 ;; http://emacs.stackexchange.com/a/401/115
 
 ;; How to use this package:
 ;;
-;;   ;; Execute `modi/org-include-img-from-pdf' before saving the file.
-;;   (defun modi/org-include-img-from-pdf-before-save ()
-;;     "Execute `modi/org-include-img-from-pdf' just before saving the file."
-;;     (add-hook 'before-save-hook #'modi/org-include-img-from-pdf nil :local))
-;;   (add-hook 'org-mode-hook #'modi/org-include-img-from-pdf-before-save)
-;;   ;; Execute `modi/org-include-img-from-pdf' before exporting.
+;;   ;; Execute `org-include-img-from-pdf' before saving the file.
+;;   (defun my/org-include-img-from-pdf-before-save ()
+;;     "Execute `org-include-img-from-pdf' just before saving the file."
+;;     (add-hook 'before-save-hook #'org-include-img-from-pdf nil :local))
+;;   (add-hook 'org-mode-hook #'my/org-include-img-from-pdf-before-save)
+;;   ;; Execute `org-include-img-from-pdf' before exporting.
 ;;   (with-eval-after-load 'ox
-;;     (add-hook 'org-export-before-processing-hook #'modi/org-include-img-from-pdf))
+;;     (add-hook 'org-export-before-processing-hook #'org-include-img-from-pdf))
 
 ;;;###autoload
-(defun modi/org-include-img-from-pdf (&rest _)
-  "Convert the pdf files to image files.
+(defun org-include-img-from-pdf (&rest _)
+  "Convert pdf files to image files in org-mode bracket links.
 
-Only looks at #+HEADER: lines that have \":convertfrompdf t\"."
+    # ()convertfrompdf:t # This is a special comment; tells that the upcoming
+                         # link points to the to-be-converted-to file.
+    # If you have a foo.pdf that you need to convert to foo.png, use the
+    # foo.png file name in the link.
+    [[./foo.png]]
+"
   (interactive)
-  (when (derived-mode-p 'org-mode)
-    (save-excursion
-      (goto-char (point-min))
-      (while (search-forward-regexp
-              "^\\s-*#\\+HEADER:.*\\s-:convertfrompdf\\s-+t"
-              nil 'noerror)
-        (let* (filenoext imgext imgfile pdffile cmd)
-          ;; Keep on going on to the next line till it finds a line with
-          ;; `[[FILE]]'
+  (if (executable-find "convert")
+      (save-excursion
+        (goto-char (point-min))
+        (while (re-search-forward "^[ \t]*#\\s-+()convertfrompdf\\s-*:\\s-*t"
+                                  nil :noerror)
+          ;; Keep on going to the next line till it finds a line with bracketed
+          ;; file link.
           (while (progn
                    (forward-line 1)
-                   (not (looking-at "\\[\\[\\(.*\\)\\.\\(.*\\)\\]\\]"))))
-          (when (looking-at "\\[\\[\\(.*\\)\\.\\(.*\\)\\]\\]")
-            (setq filenoext (match-string-no-properties 1))
-            (setq imgext (match-string-no-properties 2))
-            (setq imgfile (expand-file-name (concat filenoext "." imgext)))
-            (setq pdffile (expand-file-name (concat filenoext "." "pdf")))
-            (setq cmd (concat "convert -density 96 -quality 85 "
-                              pdffile " " imgfile))
-            (when (file-newer-than-file-p pdffile imgfile)
-              ;; This block is executed only if pdffile is newer than imgfile
-              ;; or if imgfile does not exist
-              ;; https://www.gnu.org/software/emacs/manual/html_node/elisp/Testing-Accessibility.html
-              (message "%s" cmd)
-              (shell-command cmd))))))))
+                   (not (looking-at org-bracket-link-regexp))))
+          ;; Get the sub-group 1 match, the link, from `org-bracket-link-regexp'
+          (let ((link (match-string-no-properties 1)))
+            (when (stringp link)
+              (let* ((imgfile (expand-file-name link))
+                     (pdffile (expand-file-name
+                               (concat (file-name-sans-extension imgfile)
+                                       "." "pdf")))
+                     (cmd (concat "convert -density 96 -quality 85 "
+                                  pdffile " " imgfile)))
+                (when (and (file-readable-p pdffile)
+                           (file-newer-than-file-p pdffile imgfile))
+                  ;; This block is executed only if pdffile is newer than
+                  ;; imgfile or if imgfile does not exist.
+                  (shell-command cmd)
+                  (message "%s" cmd)))))))
+    (user-error "`convert' executable (part of Imagemagick) is not found")))
 
 
 (provide 'org-include-img-from-pdf)

setup-files/setup-org.el

@@ -1,4 +1,4 @@
-;; Time-stamp: <2017-04-04 17:15:39 kmodi>
+;; Time-stamp: <2017-04-04 23:03:22 kmodi>
 ;; Hi-lock: (("\\(^;\\{3,\\}\\)\\( *.*\\)" (1 'org-hide prepend) (2 '(:inherit org-level-1 :height 1.3 :weight bold :overline t :underline t) prepend)))
 ;; Hi-Lock: end
 
@@ -611,14 +611,14 @@ the languages in `modi/ob-enabled-languages'."
       :load-path "elisp/org-include-img-from-pdf"
       :config
       (progn
-        ;; ;; Execute `modi/org-include-img-from-pdf' before saving the file.
+        ;; ;; Execute `org-include-img-from-pdf' before saving the file.
         ;; (defun modi/org-include-img-from-pdf-before-save ()
-        ;;   "Execute `modi/org-include-img-from-pdf' just before saving the file."
-        ;;   (add-hook 'before-save-hook #'modi/org-include-img-from-pdf nil :local))
+        ;;   "Execute `org-include-img-from-pdf' just before saving the file."
+        ;;   (add-hook 'before-save-hook #'org-include-img-from-pdf nil :local))
         ;; (add-hook 'org-mode-hook #'modi/org-include-img-from-pdf-before-save)
-        ;; Execute `modi/org-include-img-from-pdf' before exporting.
+        ;; Execute `org-include-img-from-pdf' before exporting.
         (with-eval-after-load 'ox
-          (add-hook 'org-export-before-processing-hook #'modi/org-include-img-from-pdf))))
+          (add-hook 'org-export-before-processing-hook #'org-include-img-from-pdf))))
 
 ;;; Extract image from included .zip
     ;; Auto extract images from zip files when saving org files.