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

[Espen Isaksen]

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
-------------- next part --------------
0,0,0
0,0,224
0,0,255
0,153,0
0,208,104
100,100,100
100,100,255
10,10,10
102,102,102
102,51,51
105,105,105
108,189,243
108,190,232
109,187,239
110,110,110
115,117,208
119,215,81
123,123,123
128,0,128
130,130,130
135,151,115
140,140,140
144,108,0
144,238,144
150,150,150
150,80,0
152,251,152
153,102,0
153,102,102
153,102,51
153,153,153
153,204,102
153,204,255
153,255,255
160,160,160
175,175,175
176,78,239
177,177,168
178,157,30
180,156,30
180,180,180
1,80,195
182,231,182
184,255,166
187,187,187
190,190,170
192,192,0
194,255,166
196,255,188
200,200,145
200,200,200
20,20,141
20,20,20
202,193,176
204,102,153
204,153,102
204,84,39
210,150,60
210,180,140
211,211,211
215,215,215
216,245,203
217,64,51
219,219,183
220,220,200
220,220,220
223,217,197
230,230,230
230,234,80
231,232,24
235,163,89
235,235,235
240,240,240
244,213,66
246,246,77
246,252,195
248,248,201
250,250,250
25,25,25
253,163,30
25,32,24
253,240,196
255,0,0
255,0,255
255,144,0
255,153,204
255,165,0
255,231,208
255,246,77
255,255,102
255,255,204
255,255,255
255,255,51
255,255,68
255,255,69
25,69,125
30,30,30
50,50,50
51,102,204
51,153,0
51,153,102
51,153,255
57,105,141
60,60,60
73,101,54
74,164,22
79,162,68
80,120,220
80,80,80
84,86,220
87,118,69
90,40,30
98,98,93
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