Generating “theme gradient” legend graphics from MapGuide Open Source

Question

In MapGuide Open Source, I've defined 10 layers, along with a theme for each. As I understand it, a theme represents how different data values are represented. For each theme, I picked two colors and created a gradient from the lowest data value to the highest.

On my map, I use WMS to render the layers. They render properly, with theming visible. However, I'd also like to generate a legend graphic for the theme.

I've tried this request: /mapguide/mapagent/mapagent.fcgi?version=1.0.0&operation=getlegendimage&THEMECATEGORY=-1&TYPE=-1&format=image/PNG&SCALE=44076.203877482876&layerdefinition=Library://OneOfMyLayers.LayerDefinition. However, that only returns a 16x16 pixel representation of a single point.

Instead, I want a graphic that displays the theme gradient. This is a standard WMS function, yet I haven't found any way to do it out of MapGuide Open Source.

Is there any way to generate such a theme gradient legend with MapGuide Open Source?

Answer 1

Does it work with unique values?

The gradient theme should not be a continous gradient but a color mapping to however many classes you have defined. I am guessing you want a to-from return.

I can't find anything about this in the documentation.

However did see a post stating that the object (talking about a google map legend) was not supported in MGOS but was implemented in the external providers widget.

Then I found this thread that you may have already seen.

LegendURL