Added --webtex option for HTML math.

+ Added --webtex command-line option, with optional parameter.
  (Defaults to using google charts API.)
+ Added WebTeX HTMLMathMethod.
+ Removed MimeTeX HTMLMathMethod.  (WebTeX is generic and subsumes it.)
+ Modified --mimetex option to use WebTeX.
+ Thanks to lpeterse for the idea and some of the code.

6 files changed, 70 insertions, 30 deletions

diff --git a/README b/README
index 33af139a4..6c3a61ca5 100644
--- a/README
+++ b/README
@@ -351,8 +351,8 @@ For further documentation, see the `pandoc(1)` man page.
     directly; this provides portability at the price of efficiency. If
     you plan to use math on several pages, it is much better to link to
     a copy of `LaTeXMathML.js`, which can be cached. (See `--jsmath`,
-    `--gladtex`, and `--mimetex` for alternative ways of dealing with
-    math in HTML.)
+    `--gladtex`, `--webtex`, and `--mimetex` for alternative ways of
+    dealing with math in HTML.)
 
 `--mathml`
 :   causes `pandoc` to convert all TeX math to MathML.
@@ -364,21 +364,29 @@ For further documentation, see the `pandoc(1)` man page.
     TeX math in HTML, Slidy, or S5. The *url* should point to the jsMath
     load script (e.g. `jsMath/easy/load.js`). If it is provided, a link
     to it will be included in the header of standalone HTML documents.
-    (See `--latexmathml`, `--mimetex`, and `--gladtex` for alternative
-    ways of dealing with math in HTML.)
+    (See `--latexmathml`, `--mimetex`, `--webtex`, and `--gladtex` for
+    alternative ways of dealing with math in HTML.)
 
 `--gladtex`*[=url]*
 :   causes TeX formulas to be enclosed in `<eq>` tags in HTML, Slidy, or
     S5 output. This output can then be processed by [gladTeX] to produce
     links to images with the typeset formulas. (See `--latexmathml`,
-    `--jsmath`, and `--mimetex` for alternative ways of dealing with
-    math in HTML.)
+    `--jsmath`, `--webtex`, and `--mimetex` for alternative ways of
+    dealing with math in HTML.)
 
 `--mimetex`*[=url]*
 :   causes TeX formulas to be replaced by `<img>` tags linking to the
     [mimeTeX] CGI script, which will produce images with the typeset
-    formulas.  (See `--latexmathml`, `--jsmath`, and `--gladtex` for alternative
-    ways of dealing with math in HTML.)
+    formulas. (See `--latexmathml`, `--jsmath`, `--webtex`, and
+    `--gladtex` for alternative ways of dealing with math in HTML.)
+
+`--webtex`*[=url]*
+:   causes TeX formulas to be replaced by `<img>` tags linking to an
+    external service that converts TeX formulas to images. The formula
+    will be concatenated with the URL provided. If no URL
+    is specified, the Google Chart API is used. (See `--latexmathml`,
+    `--jsmath`, `--mimetex`, and `--gladtex` for alternative ways of
+    dealing with math in HTML.)
 
 `-i` or `--incremental`
 :   causes all lists in Slidy or S5 output to be displayed incrementally by
@@ -1241,6 +1249,12 @@ command-line options selected:
         gladtex -d myfile-images myfile.htex
         # produces myfile.html and images in myfile-images
 
+6.  If the `--webtex` option is used, TeX formulas will be converted
+    to `<img>` tags that link to an external script that converts
+    formulas to images. The formula will be URL-encoded and concatenated
+    with the URL provided. If no URL is specified, the Google Chart
+    API will be used (`http://chart.apis.google.com/chart?cht=tx&chl=`).
+
 Inline TeX
 ----------
 
diff --git a/man/man1/pandoc.1.md b/man/man1/pandoc.1.md
index c829aacae..e1cf67847 100644
--- a/man/man1/pandoc.1.md
+++ b/man/man1/pandoc.1.md
@@ -136,6 +136,11 @@ should pipe input and output through `iconv`:
 :   Render TeX math using the mimeTeX CGI script.  If *URL* is not specified,
     it is assumed that the script is at `/cgi-bin/mimetex.cgi`.
 
+\--webtex=*URL*
+:   Render TeX math using an external script. The formula will be
+    concatenated with the URL provided. If *URL* is not specified, the
+    Google Chart API will be used.
+
 -i, \--incremental
 :   Make list items in Slidy or S5 display incrementally (one by one).
 
diff --git a/src/Text/Pandoc/Shared.hs b/src/Text/Pandoc/Shared.hs
index ac1cf7373..b8eb14177 100644
--- a/src/Text/Pandoc/Shared.hs
+++ b/src/Text/Pandoc/Shared.hs
@@ -457,7 +457,7 @@ data HTMLMathMethod = PlainMath
                     | LaTeXMathML (Maybe String)  -- url of LaTeXMathML.js
                     | JsMath (Maybe String)       -- url of jsMath load script
                     | GladTeX
-                    | MimeTeX String              -- url of mimetex.cgi 
+                    | WebTeX String               -- url of TeX->image script.
                     | MathML (Maybe String)       -- url of MathMLinHTML.js
                     deriving (Show, Read, Eq)
 
diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 3f9a417d2..20022e182 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -36,6 +36,7 @@ import Text.Pandoc.Templates
 import Text.Pandoc.Readers.TeXMath
 import Text.Pandoc.Highlighting ( highlightHtml )
 import Text.Pandoc.XML (stripTags, escapeStringForXML)
+import Network.HTTP ( urlEncode )
 import Numeric ( showHex )
 import Data.Char ( ord, toLower )
 import Data.List ( isPrefixOf, intersperse )
@@ -462,16 +463,20 @@ inlineToHtml opts inline =
                                   -- non-math elements on the page from being treated as math by
                                   -- the javascript
                                   return $ thespan ! [theclass "LaTeX"] $
-                                             if t == InlineMath
-                                                 then primHtml ("$" ++ str ++ "$")
-                                                 else primHtml ("$$" ++ str ++ "$$")
-                               JsMath _ ->
-                                  return $ if t == InlineMath
-                                              then thespan ! [theclass "math"] $ primHtml str
-                                              else thediv ! [theclass "math"]  $ primHtml str
-                               MimeTeX url -> 
-                                  return $ image ! [src (url ++ "?" ++ str),
-                                                    alt str, title str]
+                                         case t of
+                                           InlineMath  -> primHtml ("$" ++ str ++ "$")
+                                           DisplayMath -> primHtml ("$$" ++ str ++ "$$")
+                               JsMath _ -> do
+                                  let m = primHtml str
+                                  return $ case t of
+                                           InlineMath -> thespan ! [theclass "math"] $ m
+                                           DisplayMath -> thediv ! [theclass "math"] $ m
+                               WebTeX url -> do
+                                  let m = image ! [src (url ++ urlEncode str),
+                                                         alt str, title str]
+                                  return $ case t of
+                                            InlineMath  -> m
+                                            DisplayMath -> br +++ m +++ br
                                GladTeX ->
                                   return $ primHtml $ "<EQ>" ++ str ++ "</EQ>"
                                MathML _ -> do
@@ -484,12 +489,14 @@ inlineToHtml opts inline =
                                         Right r -> return $ primHtml $
                                                     ppcElement conf r
                                         Left  _ -> inlineListToHtml opts
-                                                    (readTeXMath str) >>=
-                                                      return . (thespan !
-                                                      [theclass "math"])
-                               PlainMath ->
-                                  inlineListToHtml opts (readTeXMath str) >>=
-                                  return . (thespan ! [theclass "math"]) ) 
+                                                   (readTeXMath str) >>= return .
+                                                     (thespan !  [theclass "math"])
+                               PlainMath -> do
+                                  x <- inlineListToHtml opts (readTeXMath str)
+                                  let m = thespan ! [theclass "math"] $ x
+                                  return  $ case t of
+                                             InlineMath  -> m
+                                             DisplayMath -> br +++ m +++ br )
     (TeX str)        -> case writerHTMLMathMethod opts of
                               LaTeXMathML _ -> do modify (\st -> st {stMath = True})
                                                   return $ primHtml str
diff --git a/src/pandoc.hs b/src/pandoc.hs
index 38db4c6df..9546d6026 100644
--- a/src/pandoc.hs
+++ b/src/pandoc.hs
@@ -40,7 +40,6 @@ import System.Environment ( getArgs, getProgName, getEnvironment )
 import System.Exit ( exitWith, ExitCode (..) )
 import System.FilePath
 import System.Console.GetOpt
-import Data.Maybe ( fromMaybe )
 import Data.Char ( toLower, isDigit )
 import Data.List ( intercalate, isSuffixOf )
 import System.Directory ( getAppUserDataDirectory )
@@ -282,11 +281,24 @@ options =
 
     , Option "" ["mimetex"]
                  (OptArg
-                  (\arg opt -> return opt { optHTMLMathMethod = MimeTeX
-                                  (fromMaybe "/cgi-bin/mimetex.cgi" arg)})
+                  (\arg opt -> do
+                      let url = case arg of
+                                      Just u   -> u ++ "?"
+                                      Nothing  -> "/cgi-bin/mimetex.cgi?"
+                      return opt { optHTMLMathMethod = WebTeX url })
                   "URL")
                  "" -- "Use mimetex for HTML math"
 
+    , Option "" ["webtex"]
+                 (OptArg
+                  (\arg opt -> do
+                      let url = case arg of
+                                      Just u   -> u
+                                      Nothing  -> "http://chart.apis.google.com/chart?cht=tx&chl="
+                      return opt { optHTMLMathMethod = WebTeX url })
+                  "URL")
+                 "" -- "Use web service for HTML math"
+
     , Option "" ["jsmath"]
                  (OptArg
                   (\arg opt -> return opt { optHTMLMathMethod = JsMath arg})
diff --git a/tests/writer.html b/tests/writer.html
index b8296a536..adf0bb9ca 100644
--- a/tests/writer.html
+++ b/tests/writer.html
@@ -855,9 +855,11 @@ Blah
 	></span
       >-Tree</li
     ><li
-    >Here’s some display math: <span class="math"
+    >Here’s some display math: <br
+       /><span class="math"
       >$\frac{d}{dx}f(x)=\lim_{h\to 0}\frac{f(x+h)-f(x)}{h}$</span
-      ></li
+      ><br
+       /></li
     ><li
     >Here’s one that has a line break in it: <span class="math"
       >α + ω × <em