Mathematics in PowerPoint 2007

I've never used PowerPoint, but I've been investigating recently the mathematical and in particular MathML capabilities of the Office 2007 suite.

It's been noted in several places that PowerPoint doesn't support the new Word 2007 math zones and that if you cut and paste a math expression from Word to PowerPoint, the result is an image, which means you can't edit it or search on it in that form, and it looks horrible on screen, especially if you have background colour or textures applied to your slides.

This note is just to mention a mechanism of getting correctly rendered editable mathematical text into PowerPoint, in a form which has the full oomml XML markup in the pptx file, so you can extract that and convert to MathML if needed using the Microsoft supplied stylesheet. I suspect that this mechanism is (or ought to be) well known by anyone (not me!) who's used PowerPoint, but a google search didn't show up anyone else mentioning it in this context, so I thought I'd post...

To get a math expression inserted, don't cut and paste a math zone from word, in Powerpoint choose
insert / Object /MicroSoft Word Document
then make a 'document' consisting of the equation you need using the embedded copy of Word. the resulting equation will be saved as an embedded object, and if you unzip the pptx PowerPoint file you will find a docx version of the embedded object in the embeddings directory, which you can further unzip to locate the oomml math XML.

The resulting equation renders as text rather than an image and may be edited at any time later, just click on it and you get thrown into a copy of Word.

Screen shot with one of Word's example equations rendered twice in a PowerPoint slide, once as an embedded object and once as an image.

XHTML and MathML from OpenOffice.org 2.2

In the comments on Murray's blog I commented that (given a fixed stylesheet that does the conversion) the workflow to extract MathML from an XML file that contains MathML, and one that contains some XML transformable to MathML is pretty much the same.

This was in reply to a comment that Science (and it turns out, Nature) don't accept Office 2007 native format, partly at least due to a perceived lack of MathML support.

So, I thought I'd repeat my recent experiment Using OpenOffice.org rather than MS Office 2007.

I took the test1.docx file used as the test file in the earlier post, saved it (using Office 2007) as .doc (which warned me that the mathematics would get turned into pictures) and then imported it into OpenOffice.org, regenerated the mathematics using the formula editor provided, deleting the Word generated images, and saved as .odt. Now the aim of the game is to get an XHTML+MathML document, starting from here...

Step 1

Save as html. This produces a passable approximation to HTML (not valid but not quite so fanciful as the output from MS Word). The Mathematics is all images, and unlike Word there is no comment or other markup (not even an alt attribute) to give an alternative format. However there is a name attribute which gives the original object name, so we can retrieve the MathML from the .odt file.

Step 2

Unzip the odt file.

Step 3

Add an (empty) file math.dtd to several subdirectories extracted from the zip file, to make the content.xml files containing MathML well formed. (A catalogue would be a more sensible alternative to supplying multiple copies of the dtd).

Step 4

Run a small stylesheet that imports htmlparse.xsl to convert the HTML to XHTML, replaces the math images by their matching MathML fragments, and does a bit more cleanup on the xhtml to make it valid.

Step 5

There is no step 5:-)

The stylesheet in step 4 looks like this:

<xsl:stylesheet 
    version="2.0"
    xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://www.w3.org/1999/xhtml"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:d="data:,dpc"> 
  <xsl:import href="../htmlparse/htmlparse.xsl"/>
  <xsl:template name="main">
    <xsl:processing-instruction name="xml-stylesheet"
     >type="text/xsl" href="pmathml.xsl"</xsl:processing-instruction>
    <xsl:apply-templates select="d:htmlparse(
     unparsed-text('test1oo.html','windows-1252'))"/>

  </xsl:template>
  <xsl:template match="@*|node()">
    <xsl:copy>
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="@align|@valign|@dir|@frame|@rules">
    <xsl:attribute name="{name()}" select="lower-case(.)"/>
  </xsl:template>

  <xsl:template match="h:img[starts-with(@name,'Object')]">
    <xsl:copy-of select="doc(concat('odt-unzip/Object ',
                             substring-after(@name,'Object'),
                             '/content.xml'))"/>
  </xsl:template>
</xsl:stylesheet>

The result of the transformation looks like this.

Comparing the stylesheet here with the one in the earlier post you'll see that the complexity in either case is about the same. Word writes all the information into a single file (as comments) which can be a bit more convenient, but OpenOffice.org places the MathML directly in the zip file which may also have advantages. Word's HTML output takes a lot more cleaning up to be valid HTML (or XHTML) but there are tools around that do that, more or less.

Rob Weir has a recent blog entry picking up on the MathML support as a reason to go with ODF. I don't buy the argument, to be honest. It's not surprising that publications are not set up to accept the zipped xml formats from any of these systems. Publisher's in house document processes are ususally somewhat complicated and fine tuned. Tooling up to accept any new format will take them time. There are plenty of reasons to argue over which format is better in any given situation, but a general statement that storing MathML is good, and storing something transformable to MathML is bad doesn't really convince me of anything, sorry!

htmlparse, updated

There are two well known open source tools for cleaning up and fixing HTML to produce XML suitable for further processing, tidy and TagSoup.

Back in 2004 I posted some XSLT code, htmlparse.xsl, to do a similar job and used it in a few examples on the xsl-list.

When I needed such a tool for the MathML from Office post, my first thought was to use the htmlparse stylesheet. Unfortunately the output from Word was too much for the stylesheet, which couldn't cope with the Microsoft conditional declarations.

However it turned out not to be hard to extend the stylesheet, so I have updated htmlparse.xsl to fix a couple of bugs in attribute handling, and to extend it to cope with <![if !vml]> and friends. This now gives a pure XSLT route of getting from Word output to XHTML+MathML. Using the same test file as the earlier post, the stylesheet:

<xsl:stylesheet 
   version="2.0"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   xmlns:d="data:,dpc"> 
  <xsl:import href="../htmlparse/htmlparse.xsl"/>
  <xsl:import href="xhtml-mathml.xsl"/>
  <xsl:template name="main">
    <xsl:apply-templates select="d:htmlparse(
              replace(
                  unparsed-text('test1.htm','windows-1252'),
                  'http://www.w3.org/TR/REC-html40',
                  'http://www.w3.org/1999/xhtml'))"/>
  /xsl:template>
</xsl:stylesheet>

Produces an XHTML+MathML document as shown.

Although it's used here to convert an entire document, TagSoup, which interfaces to XSLT as a SAX parser, is probably preferable in this context. htmlparse (originally written just as an excercise in XSLT2 regular expressions) is probably more useful for parsing small fragments of html, as often found in query strings or embedded in CDATA in XML files. It has the advantage of being pure XSLT, not requiring any extension functions or non standard parser usage.

2009-12-18 updated location of htmlparse to google code