[mapguide-internals] PNG8 color quantization problem

Gabriele Monfardini gabrimonfa at gmail.com
Fri Jan 14 05:31:14 EST 2011

> The RFC60 was intended to correct the quantization errors of the color table
> between adjoining map tiles.
> To understand your ticket # 1518 better it would be important to know how
> the images were created.
> So please augment the ticket with the relevant information:
> 1. How is the map generated (which api calls are used)
> 2. How is the map structured. (layers and such)
> 3. Provide a sample map.

1. Basic ajax viewer, no particular api calls (the images are those
sent to the browser viewing the map)
2. The map has some groups (from five to ten) with some layers in each
(from one to five). A fairly standard map. However some layers
intersects and have transparency enabled so there are many resulting
I don't think that map structure is particularly important.
3.  This is a bit difficult for me since I'm using OGR provider
together with PostgreSQL with a custom GDAL build. If this is really
needed (you are not able to reproduce the problem) I can try to
reproduce it in a simpler map, maybe using shapefiles.

Since using JPG  seems to have some problem in MGOS 2.2RC1 and PNG
produces far bigger images, these bug has become a very important one
for me (and in general, since there are may situations where color
fidelity and stability is important).


Gabriele Monfardini

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