Clickable maps (clickmaps) allow browser users to click on a region in a graphic, which acts as a hyperlink to a new web page. Ploticus 2.03+ can generate either server-side or client-side map files to accompany images (PNG, JPEG, or GIF); version 2.04+ supports clickable mapping in SVG. For images, map info is written to a separate file. For SVG, the mapping information is added to the .svg / .svgz output file (so the server-side vs. client-side distinction discussed below is moot).

You can map pie slice labels , bars , scatterplot points , annotations , legend entries , and the plotting area (either as a grid, or in its entirety).

Examples

Server-side maps vs. client-side maps

Generating map files

You can use the -mapfile command line option (or proc page equivalent) to explicitly name your map file; otherwise the map file will have the same name as the accompanying graphic result file, except with a .map suffix.

Usage examples:

pl -png -map -prefab pie ...
pl -png -map pie3.pl
pl -png -csmap pie3.pl
pl -svgz -map results4.pl

You will need to supply URL information (discussed below) in your script or prefab for hyperlink purposes.

HTML usage

In your web pages, you can use the following HTML construct to associate a server-side map file with an image:

    <a href="mypic.map"> <img src="mypic.png" ismap > </a>

Here's an HTML example that uses an embedded client-side map for an image:

   <img src="mypic.png" usemap="#map1">
   <map name="map1">
   ... the map content that pl generates will go here ...
   </map>

Note: When ploticus generates a client-side map, it leaves off the opening <map> and closing </map> tags. These tags will need to be added by the user.

For SVG, no special action is necessary; use the normal construct.

Troubleshooting

Note that if two generated mapped regions overlap, they are stacked in the order generated (the last generated is on "top").

Specifying URLs

For pie graphs, bar graphs, and scatterplots:

Use proc pie / bars / scatterplot attribute clickmapurl to specify a URL template. The template may contain data field references prefaced by two at-signs (@@). For example:

	clickmapurl: http://abc.com/mycgi?id=@@3

would generate a URL for each pie slice label, bar, scatterplot point, etc., using the value in data field 3 for each. This example:

	clickmapurl: @@6

would take the URL for each slice, bar, etc. from data field 6. URL templates work well for typical CGI invocations where the CGI script name is constant and the parameters vary. If you have a collection of non-uniform URLs that you wish to map, they may be listed in a data field and accessed there.

For annotations:

Use proc annotate attribute clickmapurl to specify a URL explicitly. For example:

	clickmapurl: http://abc.com/docs/aboutpets.html

For legend entries:

Embed a URL into the legendlabel attribute (or if you are using proc legendentry the label attribute). Use this format: url:url label
See this example: clickmap_leg

For the plotting area to be a single region:

Use proc areadef attribute clickmapurl to specify a URL. XVAL and YVAL do not apply.

For grid regions within the plotting area:

Use proc areadef attribute clickmapurl to specify a URL template. The template should contain special symbols @@XVAL and/or @@YVAL. For example:

	clickmapurl: http://abc.com/mycgi?x=@@XVAL&y=@@YVAL

Then use proc axis attribute clickmap for either the X axis, the Y axis, or both.

• For a clickmap responding to different values in X, the above URL template should contain @@XVAL, and set proc xaxis attribute clickmap: grid.
• For a clickmap responding to different values in Y, the above URL template should contain @@YVAL, and set proc yaxis attribute clickmap: grid.
• For a clickmap responding to different values in X and Y, the above URL template should contain both @@XVAL and @@YVAL, and set proc xaxis attribute clickmap: xygrid and proc yaxis attribute clickmap: xygrid.

The mapped regions will be centered around stubs. Stub values will be substituted into the URL template as XVAL and YVAL. These stub values will use the default format (not necessarily the displayed stub format) for the particular scale unit but this can be controlled using proc axis clickmapvalformat attribute. By default the regions will stop at the plotting area boundary, but they can be extended (to encompass stubs for example) using proc axis clickmapextent attribute.

If you need higher (or lower) granularity than what your stubs provide, you can invoke an additional, invisible X axis using the desired granularity like this:

	#proc xaxis
	stubs: inc <whatever>
	clickmap: grid
	axisline: no
 	tics: no
	stubomit: *

To set a default URL for the entire image:

Use proc page attribute clickmapdefault to specify a default URL that will be invoked if the mouse click is not in a defined region.

Notes:

Embedded spaces and newlines that turn up within URLs will be converted to underscores.

Grid mapping may not be used with more than one plotting area per image.

Examples