[mapserver-users] Use of palette file: Problems with changingcolors when tiling

[Steve Lime]

Is the color 125,202,228 (the water value in the image on the left) used in your mapfile?

>>> On 10/28/2009 at 5:25 AM, in message
<a4cd3760910280325l4c4a1feah93782aeb259462d2 at mail.gmail.com>, Espen Isaksen
<espen.isaksen at gmail.com> wrote:
> 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