[mapserver-users] Map File for Open Street Map symbology

[Stephen Woodbridge]

thomas bonfort wrote:
> http://code.google.com/p/mapserver-utils/source/browse/trunk/
> 
> you'll need the code from the mapserver graphics sandbox (rev 8254 is
> preferred as it doesn't have the cairo code in it yet)

Hi Thomas,

I have been looking over your osm mapfile and have a few questions.

1) As you mentioned in your original post, I should grab some code from 
a sandbox, what does this have in it over say todays svn?

2) I noticed you have both:

     LABELITEM "name"
and
         TEXT ([ref])

Does the TEXT override the LABELITEM for the given class it is in? and 
then default to the LABELITEM if it is not present? I guess this seems 
logical, but I never thought about it before.

3) This looks a little strange. It looks like you are drawing the 
outline first without the body of the road, then drawing the body of the 
road afterwards.

         STYLE
             WIDTH _motorway_width
             OUTLINEWIDTH 1
             OUTLINECOLOR _motorway_ol_clr
             MINWIDTH _motorway_minwidth
             MAXWIDTH _motorway_maxwidth
         END
         STYLE
             WIDTH _motorway_width
             COLOR _motorway_clr
             MINWIDTH _motorway_minwidth
             MAXWIDTH _motorway_maxwidth
         END

Why not draw it like in a single pass? are there quality issues with this?

         STYLE
             WIDTH _motorway_width
             COLOR _motorway_clr
             OUTLINEWIDTH 1
             OUTLINECOLOR _motorway_ol_clr
             MINWIDTH _motorway_minwidth
             MAXWIDTH _motorway_maxwidth
         END

Or draw it like where (_motorway_width + 2) is a value not an expression:

         STYLE
             WIDTH _motorway_width + 2
             COLOR _motorway_ol_clr
             MINWIDTH _motorway_minwidth
             MAXWIDTH _motorway_maxwidth
         END
         STYLE
             WIDTH _motorway_width
             COLOR _motorway_clr
             MINWIDTH _motorway_minwidth
             MAXWIDTH _motorway_maxwidth
         END

I assume this is slower because you have to draw all the pixels between 
the outlines.

4) I have not seen MINWIDTH and MAXWIDTH before. What do these do? Isn't 
the width fixed? Or is this controlling the how wide the antialiasing is 
allowed to propagate?

Wow! After 10 years of working with mapfile files there is still a lot 
of new interesting stuff to learn!

Thank you for sharing this!

Best regards,
   -Steve W