ox-odt: Include #+latex_header when converting LaTeX to PNG

* lisp/ox-odt.el (org-odt--translate-latex-fragments): Include
  #+latex_header when converting LaTeX to PNG.

Reported-by: edgar@openmail.cc
<http://lists.gnu.org/archive/html/emacs-orgmode/2017-06/msg00480.html>

lisp/ox-odt.el

@@ -112,7 +112,9 @@
     (:odt-table-styles nil nil org-odt-table-styles)
     (:odt-use-date-fields nil nil org-odt-use-date-fields)
     ;; Redefine regular option.
-    (:with-latex nil "tex" org-odt-with-latex)))
+    (:with-latex nil "tex" org-odt-with-latex)
+    ;; Retrieve LaTeX header for fragments.
+    (:latex-header "LATEX_HEADER" nil nil newline)))
 
 
 ;;; Dependencies
@@ -3731,42 +3733,45 @@ contextual information."
 		    (mathml (format "Creating MathML snippet %d..." count))))
 		 ;; Get an Org-style link to PNG image or the MathML
 		 ;; file.
-		 (org-link
-		  (let ((link (with-temp-buffer
-				(insert latex-frag)
-				(org-format-latex cache-subdir nil nil cache-dir
-						  nil display-msg nil
-						  processing-type)
-				(buffer-substring-no-properties
-				 (point-min) (point-max)))))
-		    (if (string-match-p "file:\\([^]]*\\)" link) link
-		      (message "LaTeX Conversion failed.")
-		      nil))))
-	    (when org-link
+		 (link
+		  (with-temp-buffer
+		    (insert latex-frag)
+		    ;; When converting to a PNG image, make sure to
+		    ;; copy all LaTeX header specifications from the
+		    ;; Org source.
+		    (unless (eq processing-type 'mathml)
+		      (let ((h (plist-get info :latex-header)))
+			(when h
+			  (insert "\n"
+				  (replace-regexp-in-string
+				   "^" "#+LATEX_HEADER: " h)))))
+		    (org-format-latex cache-subdir nil nil cache-dir
+				      nil display-msg nil
+				      processing-type)
+		    (goto-char (point-min))
+		    (org-element-link-parser))))
+	    (if (not (eq 'link (org-element-type link)))
+		(message "LaTeX Conversion failed.")
 	      ;; Conversion succeeded.  Parse above Org-style link to
 	      ;; a `link' object.
-	      (let* ((link
-		      (org-element-map
-			  (org-element-parse-secondary-string org-link '(link))
-			  'link #'identity info t))
-		     (replacement
-		      (cl-case (org-element-type latex-*)
-			;; Case 1: LaTeX environment.  Mimic
-			;; a "standalone image or formula" by
-			;; enclosing the `link' in a `paragraph'.
-			;; Copy over original attributes, captions to
-			;; the enclosing paragraph.
-			(latex-environment
-			 (org-element-adopt-elements
-			  (list 'paragraph
-				(list :style "OrgFormula"
-				      :name
-				      (org-element-property :name latex-*)
-				      :caption
-				      (org-element-property :caption latex-*)))
-			  link))
-			;; Case 2: LaTeX fragment.  No special action.
-			(latex-fragment link))))
+	      (let ((replacement
+		     (cl-case (org-element-type latex-*)
+		       ;;LaTeX environment.  Mimic a "standalone image
+		       ;; or formula" by enclosing the `link' in
+		       ;; a `paragraph'.  Copy over original
+		       ;; attributes, captions to the enclosing
+		       ;; paragraph.
+		       (latex-environment
+			(org-element-adopt-elements
+			 (list 'paragraph
+			       (list :style "OrgFormula"
+				     :name
+				     (org-element-property :name latex-*)
+				     :caption
+				     (org-element-property :caption latex-*)))
+			 link))
+		       ;; LaTeX fragment.  No special action.
+		       (latex-fragment link))))
 		;; Note down the object that link replaces.
 		(org-element-put-property replacement :replaces
 					  (list (org-element-type latex-*)