[mapguide-internals] Selection is slower than expected

Paul Spencer pspencer at dmsolutions.ca
Wed Sep 5 08:20:52 EDT 2007


this is probably a good idea.  I think it would need to use a PNG24  
with alpha channel so that the selection image doesn't obscure  
things, but this raises potential problems (for which there are known  
hacks) for Internet Explorer.  If we forgo transparency in the actual  
selected area, then it may work without hacks - but then you would  
lose anti-aliasing of the selection polygon.

The GETDYNAMICOVERLAYMAP operation already produces something with  
transparency for overlaying on tiles.  A similar operation could be  
created, GETDYNAMICOVERLAYSELECTION perhaps, that just draws the  
selection.  I would hope that would be fairly straightforward -  
although I don't think you can do it with the web tier scripting APIs  
as is.

I guess this is what the DWF viewer has an advantage over the AJAX  
viewer - client side selection.



On 5-Sep-07, at 3:33 AM, Kenneth, GEOGRAF A/S wrote:

> When selecting items in map, a full new map image is generated.
> This requires rendereing the entire map, and then transfering the  
> entire map to the client.
> Has anyone tried to implement the selection as a transparent png,  
> containing only the selected graphics (overlay image)?
> This procedure is potentially very fast to render, and certainly  
> has a much smaller size.
> Are there any issues that would obstruct such an implementation?
> -- 
> Regards, Kenneth, GEOGRAF A/S
> _______________________________________________
> mapguide-internals mailing list
> mapguide-internals at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-internals

|Paul Spencer                          pspencer at dmsolutions.ca    |
|Chief Technology Officer                                         |
|DM Solutions Group Inc                http://www.dmsolutions.ca/ |

More information about the mapguide-internals mailing list