[mapserver-users] Re: Use of palette file: Problems with changing colors when tiling

[Espen Isaksen]

Justed wanted to bring this question into attention again since we did
not get a solution to the problem, and we have not found one either.

Could this possibly be a bug in Mapserver? Should we report it?

Espen



2009/10/28 Espen Isaksen <espen.isaksen at gmail.com>:
> Hi!
>
> We are testing out using a palette file in our outputformat to
> decrease file size in the png output. Most of the time this works
> great, but some times when we are tiling the data we get some errors.
> The color seem to shift to a similar color from one tile to another.
>
> We have added the colors we use in the map file in the palette.txt
> file. The documentation says it needs 256 colors in the map file, but
> we do not use that many colors right now. (we tried adding the same
> color more than one time, but that created other problems....)
>
> I have attached a png file showing the problem across a lake. The
> color on the right side is the correct color and the color we have
> added to the palette file. The color on the left side of the lake is
> not something we have set.
>
> I have also added the palette.txt file and the outputformat we use is this:
>
>         OUTPUTFORMAT
>                        NAME             "png"
>                        DRIVER           "AGG/PNG"
>                        MIMETYPE         "image/png"
>                        IMAGEMODE        "rgb"
>                        EXTENSION        "png"
>                        FORMATOPTION     "PALETTE_FORCE=TRUE"
>                        FORMATOPTION     "PALETTE=/data/maps/palette.txt"
>                 END
>
> Does anybody know why this happens in Mapserver and how to fix it?
>
> Espen
>