[mapserver-dev] Undocumented Mapfile COLOR options

[Lars Schylberg]

Hello All,

I wrote about this as my Mapserver Easteregg findings two years ago:

https://lists.osgeo.org/pipermail/mapserver-users/2018-March/080547.html

I also made some different examples in my GIST:

https://gist.github.com/LarsSchy/df91553f1fda02196ba7881a129b4c64

I am not really sure how useful this is.

Sometimes when I want to make color tranparent I throw in a -1 in the 
red color column, just because I know I can.

Happy summer

Lars Schylberg


Den 2020-07-22 kl. 23:45, skrev Seth G:
> Hi all,
>
> Whilst validating various Mapfiles to try and find all valid options I've come across a couple of special values used in msautotest Mapfiles for COLOR - the first is -255 -255 -255 used in classtest1.map [1]
>
> CLASS
>      NAME "Text"
>      EXPRESSION ([pixel] == 0)
>      COLOR -255 -255 -255
> END
>
> This value is defined in mapserver.h [2] as follows:
>
> #define MS_TRANSPARENT_COLOR(color) (((color).alpha==0 || (color).red==-255 || (color).green==-255 || (color).blue==-255)?MS_TRUE:MS_FALSE)
>
> So can this be set to make a color transparent? Is it a valid value and if so should this be added somewhere in the docs? There is currently no reference.
>
> The second example is:
>
> BACKGROUNDCOLOR -1 -1 -1
>
> LABEL BACKGROUNDCOLOR was removed in 6.0 [3] but is still present in mapserver\msautotest\misc\sde_utf2.map
>
> One of the Python MapScript tests refers to this value as an "invalid color" that should throw an error [4]
>
> Any details on these 2 COLOR values appreciated,
>
> Seth
>
>
> [1] https://github.com/mapserver/mapserver/blob/85e294e8c8ce3c9c455fea0137d4af1ee2feced0/msautotest/gdal/classtest1.map#L33
> [2] https://github.com/mapserver/mapserver/blob/06a076e9d0992f3ace676933ddcde87985feea31/mapserver.h#L369
> [3] https://mapserver.org/mapfile/label.html#mapfile-label-backgroundcolor
> [4] https://github.com/mapserver/mapserver/blob/85e294e8c8ce3c9c455fea0137d4af1ee2feced0/mapscript/python/tests/cases/color_test.py#L50
>
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