[mapguide-users] patch for Ticket #743 / png8 transparency

[Zac Spitzer]

One of the issues is that with subpixel rendering using AGG, a map using
60 base colours will actually use more than 60 colours for fine edges
(so I believe)

The reason why we use a predefined palette for tiles is that for
Explore Australia,
we were having heaps of problems with the colour of ocean changing
between tiles,
obviously this is less of a problem with a single image dynamic map.

Perhaps the ultimate solution would be to feed to predefined palette into the
the quantization routines as a hint, with any used predefined colours being
discarded. Perhaps this could be triggered when a certain threshold is reached,
i.e. a full palette. An obvious example would be a map using a raster background


z

On Thu, Sep 27, 2012 at 2:33 AM, Jackie Ng <jumpinjackie at gmail.com> wrote:
> Unless I got this PNG8 quantization business all wrong, if the resulting
> image would use < 256 colors then there shouldn't be a need for the
> quantizer to compute a palette is there? Just take this list of colors that
> we've extracted out of all the Layer/Symbol Definitions and let the PNG8
> quantizer "fill in the blanks" up to the 256 colors.
>
> If we have defined these colors in our Layer/Symbol definitions, I think
> they should be respected if the total number of colors used < 256.
>
> - Jackie
>
>
>
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-- 
Zac Spitzer
Solution Architect / Director
Ennoble Consultancy Australia
+61 405 847 168