Fix generating LaTeX formula images

* lisp/ox-odt.el (org-odt--translate-latex-fragments): Fix imagemagick support.
* lisp/ox-html.el (org-html-latex-environment)
(org-html-latex-fragment): Fix imagemagick support.
* org.el (org-create-formula-image-with-imagemagick): Generate correct
size formula image.
(org-format-latex-header): Change pagestyle command position.
* doc/org.texi (@LaTeX{} fragments)
(Previewing @LaTeX{} fragments)
(Math formatting in HTML export)
(Working with @LaTeX{} math snippets): Add document about creating
formula image with imagemagick.

doc/org.texi

@@ -10156,10 +10156,10 @@ snippets will be identified as @LaTeX{} source code:
 @item
 Environments of any kind@footnote{When @file{MathJax} is used, only the
 environments recognized by @file{MathJax} will be processed.  When
-@file{dvipng} is used to create images, any @LaTeX{} environment will be
-handled.}.  The only requirement is that the @code{\begin} and @code{\end}
-statements appear on a new line, at the beginning of the line or after
-whitespaces only.
+@file{dvipng} program or @file{imagemagick} suite is used to create images,
+any @LaTeX{} environment will be handled.}.  The only requirement is that the
+@code{\begin} and @code{\end} statements appear on a new line, at the
+beginning of the line or after whitespaces only.
 @item
 Text within the usual @LaTeX{} math delimiters.  To avoid conflicts with
 currency specifications, single @samp{$} characters are only recognized as
@@ -10197,7 +10197,6 @@ lines:
 
 @example
 #+OPTIONS: tex:t          @r{Do the right thing automatically (MathJax)}
-#+OPTIONS: tex:dvipng     @r{Force using dvipng images}
 #+OPTIONS: tex:nil        @r{Do not process @LaTeX{} fragments at all}
 #+OPTIONS: tex:verbatim   @r{Verbatim export, for jsMath or so}
 @end example
@@ -11257,6 +11256,7 @@ You could use @code{http} addresses just as well.
 @subsection Math formatting in HTML export
 @cindex MathJax
 @cindex dvipng
+@cindex imagemagick
 
 @LaTeX{} math snippets (@pxref{@LaTeX{} fragments}) can be displayed in two
 different ways on HTML pages.  The default is to use the
@@ -11282,13 +11282,19 @@ this line.
 If you prefer, you can also request that @LaTeX{} fragments are processed
 into small images that will be inserted into the browser page.  Before the
 availability of MathJax, this was the default method for Org files.  This
-method requires that the @file{dvipng} program is available on your system.
-You can still get this processing with
+method requires that the @file{dvipng} program or @file{imagemagick} suite is
+available on your system.  You can still get this processing with
 
 @example
 #+OPTIONS: tex:dvipng
 @end example
 
+or:
+
+@example
+#+OPTIONS: tex:imagemagick
+@end example
+
 @node Text areas in HTML export, CSS support, Math formatting in HTML export, HTML export
 @subsection Text areas in HTML export
 
@@ -12265,17 +12271,25 @@ and open the formula file with the system-registered application.
 @end table
 
 @cindex dvipng
+@cindex imagemagick
 @item PNG images
 
 This option is activated on a per-file basis with
 
 @example
-#+OPTIONS: LaTeX:dvipng
+#+OPTIONS: tex:dvipng
+@end example
+
+or:
+
+@example
+#+OPTIONS: tex:imagemagick
 @end example
 
 With this option, @LaTeX{} fragments are processed into PNG images and the
 resulting images are embedded in the exported document.  This method requires
-that the @file{dvipng} program be available on your system.
+that the @file{dvipng} program or @file{imagemagick} suite be available on
+your system.
 @end enumerate
 
 @node Working with MathML or OpenDocument formula files,  , Working with @LaTeX{} math snippets, Math formatting in ODT export

lisp/org.el

@@ -3764,9 +3764,9 @@ images at the same place."
 \\usepackage[usenames]{color}
 \\usepackage{amsmath}
 \\usepackage[mathscr]{eucal}
-\\pagestyle{empty}             % do not remove
 \[PACKAGES]
 \[DEFAULT-PACKAGES]
+\\pagestyle{empty}             % do not remove
 % The settings below are copied from fullpage.sty
 \\setlength{\\textwidth}{\\paperwidth}
 \\addtolength{\\textwidth}{-3cm}
@@ -18609,7 +18609,7 @@ share a good deal of logic."
                   (font-height (face-font 'default))
                 (face-attribute 'default :height nil)))
 	 (scale (or (plist-get options (if buffer :scale :html-scale)) 1.0))
-	 (dpi (number-to-string (* scale (floor (* 0.9 (if buffer fnh 140.))))))
+	 (dpi (number-to-string (* scale (floor (if buffer fnh 120.)))))
 	 (fg (or (plist-get options (if buffer :foreground :html-foreground))
 		 "black"))
 	 (bg (or (plist-get options (if buffer :background :html-background))

lisp/ox-html.el

@@ -2497,7 +2497,7 @@ CONTENTS is nil.  INFO is a plist holding contextual information."
     (case processing-type
       ((t mathjax)
        (org-html-format-latex latex-frag 'mathjax))
-      (dvipng
+      ((dvipng imagemagick)
        (let ((formula-link (org-html-format-latex latex-frag processing-type)))
 	 (when (and formula-link (string-match "file:\\([^]]*\\)" formula-link))
 	   ;; Do not provide a caption or a name to be consistent with
@@ -2517,7 +2517,7 @@ CONTENTS is nil.  INFO is a plist holding contextual information."
     (case processing-type
       ((t mathjax)
        (org-html-format-latex latex-frag 'mathjax))
-      (dvipng
+      ((dvipng imagemagick)
        (let ((formula-link (org-html-format-latex latex-frag processing-type)))
 	 (when (and formula-link (string-match "file:\\([^]]*\\)" formula-link))
 	   (org-html--format-image (match-string 1 formula-link) nil info))))

lisp/ox-odt.el

@@ -3772,9 +3772,10 @@ contextual information."
 	   (setq processing-type 'mathml)
 	 (message "LaTeX to MathML converter not available.")
 	 (setq processing-type 'verbatim)))
-      (dvipng
+      ((dvipng imagemagick)
        (unless (and (org-check-external-command "latex" "" t)
-		    (org-check-external-command "dvipng" "" t))
+		    (org-check-external-command
+		     (if (eq processing-type 'dvipng) "dvipng" "convert") "" t))
 	 (message "LaTeX to PNG converter not available.")
 	 (setq processing-type 'verbatim)))
       (otherwise
@@ -3787,7 +3788,7 @@ contextual information."
     (message "Formatting LaTeX using %s" processing-type)
 
     ;; Convert `latex-fragment's and `latex-environment's.
-    (when (memq processing-type '(mathml dvipng))
+    (when (memq processing-type '(mathml dvipng imagemagick))
       (org-element-map tree '(latex-fragment latex-environment)
 	(lambda (latex-*)
 	  (incf count)
@@ -3796,13 +3797,13 @@ contextual information."
 		 (cache-dir (file-name-directory input-file))
 		 (cache-subdir (concat
 				(case processing-type
-				  (dvipng "ltxpng/")
+				  ((dvipng imagemagick) "ltxpng/")
 				  (mathml "ltxmathml/"))
 				(file-name-sans-extension
 				 (file-name-nondirectory input-file))))
 		 (display-msg
 		  (case processing-type
-		    (dvipng (format "Creating LaTeX Image %d..." count))
+		    ((dvipng imagemagick) (format "Creating LaTeX Image %d..." count))
 		    (mathml (format "Creating MathML snippet %d..." count))))
 		 ;; Get an Org-style link to PNG image or the MathML
 		 ;; file.