[mapguide-internals] RFC 40 - Support for using the AGG renderer

[Paul Spencer]

I am concerned about maintaining a fork independently of MapServer  
and other OSGeo projects that might use AGG.  I propose that the fork  
be maintained in a separate repository on OSGeo infrastructure with  
the intention of involving at least the MapServer folks, and possibly  
others that care since they have the same license issues.  Initially,  
commit access can be limited to Traian ;)

I am assuming that the AGG renderer will render into a GD buffer and  
GD will still be used to do image I/O.  Is this correct?

MapServer 5.0 includes a capability to convert PNG24 into PNG8 with a  
predetermined palette of colours that must be preserved during the  
quantization process.  I would recommend that this is looked at as  
part of this work and perhaps made available as an option.

There is a known issue with GD and how it handles the alpha channel  
that made it impossible to support alpha transparency between layers  
when MapServer implemented AGG.  I believe the issue was that GD had  
a non-standard way of looking at the 4th byte in a 32 byte buffer,  
more of an opacity rather than transparency (or the other way  
around).  Are you aware of this issue and prepared to work around  
it?  I believe the current maintainer of GD (part of PHP now) is  
aware of the issue and may fix it in a future version.

Cheers

Paul

On 19-Oct-07, at 4:35 PM, Tom Fukushima wrote:

> Hi,
>
> Please take a look at "RFC 40 - Support for using the AGG renderer"
> (http://trac.osgeo.org/mapguide/wiki/MapGuideRfc40) and post  
> feedback to
> the list.
>
> Thanks
> Tom
> _______________________________________________
> mapguide-internals mailing list
> mapguide-internals at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-internals

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