[UMN_MAPSERVER-USERS] symbols - inprecise rendering

[R. Müller]

Hi,

i've got a question concerning rendering symbols in mapserver. I'm 
working with mapserver 4.6 mostly on linux-based maschines and noticed 
that under certain circumstances the rendering of point symbols is quit 
inexactly.

in the following test-case i wanted to draw gray-filled circles with a 
black border. in this case i didn't used the newer style-syntax but the 
result is quit the same. in the rendered image the two cirlces (inner 
circle and border are not located in the same origin, one circle is 
shifted for some pixels)

symbol-definition :

   SYMBOL
     NAME 'kreis'
     TYPE ELLIPSE
     FILLED TRUE
     POINTS 1 1 END
   END

inside the layer definition :

    CLASS
        SYMBOL 'kreis'
         EXPRESSION "gray"
         COLOR 0 0 0
         SIZE 50
         OVERLAYSYMBOL 'kreis'
         OVERLAYCOLOR 200 200 200
         OVERLAYSIZE 35
         OVERLAYMAXSIZE 35
         MAXSIZE 50
     END

the data comes from a postgis-database backend, but it doesn't matter. i 
worked out the following standalone test-case (complete map-file) and 
the behaviour is the same :

MAP
  NAME 'testy'
  EXTENT 0 0 800 600
  SIZE 501 521

  IMAGETYPE PNG

  SYMBOL
    NAME 'circle'
    TYPE ELLIPSE
    POINTS 1 1 END
    FILLED TRUE
  END


  LAYER
    NAME 'kreis'
    STATUS DEFAULT
    TYPE POINT
    FEATURE
      POINTS 450 150 120 111 450 301  END
      #POINTS 350 350 END
    END
    CLASS
      STYLE
        SYMBOL 'circle'
        SIZE 101
        COLOR 0 0 0
      END
      STYLE
        SYMBOL 'circle'
        SIZE 94
        COLOR 121 121 121
      END
      TEXT 'K0025'
    END
  END


  LAYER
    NAME 'kreis1'
    STATUS DEFAULT
    TRANSPARENCY 50
    TYPE POINT
    FEATURE
      POINTS 100 450 750 320 131 310  END
      #POINTS 350 350 END
    END
    CLASS
      STYLE
        SYMBOL 'circle'
        SIZE 51
        COLOR 0 0 0
      END
      STYLE
        SYMBOL 'circle'
        SIZE 35
        COLOR 211 121 121
      END
      TEXT 'K0025'
    END
  END
END


i discovered some correlation to the version of used GDAL-library :
in one case i used Version 1.3.1 and its rendered correctly (see 3rd 
pic), in another case i used 1.2.6 and renders incorrectly (see 2nd 
pic). Can someone confirm this behaviour ?

thanks a lot in advance.

regards

ronald

attachments :

1. first example with incorrect rendering
2. standalone mapfile with incorrect rendering (GDAl 1.2.6)
2. standalone mapfile with correct rendering (GDAl 1.3.1)

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