[mapserver-users] Re: symbol position moving when using angle

[Robert Hollingsworth]

Bart,
re: recent comments about ability to POSITION a symbol in mapserver 6, (sorry, my message probably won't insert into the message thread nicely)

I wonder if any offsetting behavior would cure this problem for a ttf symbol.  Or another way to state it, I wonder if there is an inconsistency in mapserver on how it places and rotates ttf symbols.

Seems we really want this behavior:

+-----+
|  #  |
|  #  |
|  #  |
|  X  |   <-- Place the cell where the X is directly over the 
|     |       POINT object's x,y location 
|  #  |              AND also rotate the symbol around X
|     |
+-----+
^
|
and DON'T rotate the ttf symbol around this point, as appears to be the current case...

also, from your original sample image, it appears the symbol has a bit of this:
+-------+

|  #    |

|  #    |

|  #    |

|  #    |   

|       |         

|  #    |

|       |

+-------+
so, one might actually want to be able to SPECIFY an x,y offset within the character cell on which the symbol is PLACED and a separate spec for an x,y offset within the char cell on which to ROTATE  (with reasonable defaults, such as, both being the geometric center of the char cell)?

Robert


Hi Robert,

thanks for your answer, indeed that must be the explanation.

However, the ESRI software (ArcMap in this case) is doing what we expect
with the same true type font.

Best regards,
Bart

> looks to me like the 'base point' around which the symbol is defined in
> terms
> of x-y position, and therefore around which the thing will rotate -- is to
> the lower-left of the visible exclamation mark:
>
>        #
>        #
>        #
>
>        #
> x  << rotates around this
>
> while you really want something like:
>
>        #
>        #
>        #   << rotates around this point
>
>        #
>
> I'm guessing this is the normal case for most ttf's?  Can you find or
> create a ttf char that is defined like the second case?  Otherwise
> probably need to use a bitmap or just block out what you need with
> mapserver vector symbology
>
> Robert
> ======================================================
> original msg
> ======================================================
> Hi list,
>
> hopefully someone can explain the following issue to me.
>
> I am using a vector symbol (ttf), and when using no angle, it is
> positioned correctly.
>
> However, when I use ANGLE on the STYLE (using an attribute in the
> dataset), things get weird and the symbol position changes.
>
> Image brous4.png (no rotation in Mapserver, red exclamation marks are
> Mapserver, black exclamation marks are ArcMap, blue dot is the same
> Mapserver layer using a circle symbol to display the location):
>
> http://www.osgis.nl/download/mapserver/brous4.png
>
> Image brous3.png, now we rotate the symbols in Mapserver, but their
> location is moving (a simple OFFSET does not seem to be a possible
> solution however):
>
> http://www.osgis.nl/download/mapserver/brous3.png
>
> TIA for any guidance.
>
> Best regards,
> Bart
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>


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