[mapguide-internals] RFC60 - PNG8 color paletteimprovementspleasecomment

UV uvwild at gmail.com
Thu Mar 5 01:14:32 EST 2009

I think to use the palettes for other 8bit images is not a problem.. (in 
the moment the only other format is GIF) (at least in the AGG Renderer)

I agree, ideally we need some code that parses the Map with a given zoom 
level and collects colors..... base colors and provided Colors.
however, I don't think this is in the scope of this work....

As the computedPalette and the ProvidedPalette will be stored as a 
Resource I think it can be already accessed with  a GetResource API call.
Is this important enough to change the mapagent API? I am not sure.
Actually the term UserProvidedPalette from earlier messages is a 
misnomer as this concept does not make a lot of sense on a per user basis
This is not a base color map which can _replace _the base colors of the  
map definition!
Having different user palettes for different users viewing the same map 
does not make sense to me.

Furthermore I think instead of a configuration value this process can 
easily be controlled by the existence of the AdditionalColorPalette.
If its there its used (always in addition to the base color algorithm)
If its not wanted the resource reference can be simply removed.

I think parsing some XML to collect the base colors is cheap enough to 
not worry too much about computational costs. (Please correct me if I am 
As this is very closely connected with the map (until it changes) a 
resource within the map is a good place keep it.

So the idea for another RFC...
A way to define a bijective mapping from  the color definitions of a map 
to a color palette such we can replace the base colors of the map by 
providing a color palette.
Very nice one. Also on a per user basis. But not in the scope of RFC60.

Jason Birch wrote:
> And...
> Although not really part of this RFC, it would be interesting if this feature could somehow be extended to dynamic 8bit map renders as well.  The current implementation can be a bit off-putting at times as colours of important features shift considerably as you zoom in/out depending on image composition.  
> Ideally, this would be done in two ways:  first, for maps that have this option enabled, the palette would be calculated the first time the map is loaded, and cached until the map definition changes or the service is restarted.  In addition, a method like GetBasePalette would be added to the mapagent, which would return a palette definition which could then be saved as resource data and persisted across sessions.
> Jason
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