general approach to image maps

[Georges Schmitz <georges.schmitz@arcor.de>]

I'm searching for a general approach for using image maps with DocBook
and I'm not referring to the image maps of callout objects.

I'm using graphviz to produce PNGs and the corresponding MAP files, so I
can rely on correctly calculated maps. All I need is a meaningful place
for leaving some information that a specific image comes along with a
map (which of course - as external code - needs to be included into the
html code).

If I would just have to insert the map content directly after the <img>
tag, one could surely argue, that a PI (eg. dbhtml-include) could do the
job (similar to what Bob mentions in
http://www.sagehill.net/docbookxsl/InsertExtHtml.html#CodeInPage). But
this will not work for 2 reasons:

   1. PIs are only processed outside figure markup (eg. only explicit
      apply-templates="imagedata" in imageobject prevent PIs to become
      effective)
   2. I need a usemap attribute directly in the img tag

Currently for me a straightforward approach would be something like the
following:

      <figure>
         <title>ER diagram (compact) of Type Certification</title>
         <mediaobject>
            <imageobject role="fo">
               <imagedata depth="22cm" height="22cm" format="SVG"
fileref="../dot/tc-compact.svg"/>
            </imageobject>
            <imageobject role="html">
               <imagedata format="PNG" fileref="../dot/tc-compact.png"/>
               <?imagemap fileref="../dot/tc-compact.map"?>
            </imageobject>
         </mediaobject>
      </figure>

But where to start? There are 2 templates to deal with, when I
want to introduce such functionality in a customization layer

(A) (very simple)
<xsl:template match="imageobject">
just needs to be extended with a <xsl:apply-templates
select="processing-instruction()"/> for loading the map and pasting it
into the html code.

(B) (with 800 lines to big for a customization layer in my opinion)
<xsl:template name="process.image">

In (A) I would load the map into a variable, extract the map name or id,
pass it over as parameter "usemap" to the imagedata template which in
its turn passes it to the named template "process.image" (B).

But what should I do with <xsl:template name="process.image">? As I
already said, I don't think that copying and pasting such a template
into a customization layer is the right approach. Should I extend it
first on my own and than file a request to see appear such functionality
in the main distribution?

Thanks,
Georges