Curious Symbol Structure

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Curious Symbol Structure

bthoen@gisnet.com
I'm trying to learn the MapServer lore and now I'm focusing on symbols. Can
anyone tell me what the logic is where one is defining a _line_ style by
using a TYPE of ELLIPSE (instead of LINE) and POINTS definition of one (x
y) as in the symbol definition below? (This is from
http://mapserver.gis.umn.edu/docs/reference/symbology/examples).

SYMBOL
  NAME 'dashed1'
  TYPE ELLIPSE
  POINTS 1 1 END
  FILLED true
  STYLE 10 5 5 10 END
END

I'm just curious. This seems like some historical artifact from the days
when learning MapServer was hard. ;-)

The TYPE ELLIPSE seems especially weird to me. Why not TYPE LINE?

- Bill Thoen
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Re: Curious Symbol Structure

Gregor at HostGIS
> Can anyone tell me what the logic is where one is defining a
> _line_ style by using a TYPE of ELLIPSE (instead of LINE)

The line will effectively be drawn as a thicker line, which looks nicer.
Still kinda sketchy on my projects; I wish antialiasing did some good...
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Re: Curious Symbol Structure

Manfred Meier
In reply to this post by bthoen@gisnet.com
Hi,

I am interested in an answer on this question from an expert, too.

What I hope I understood from many little parts of information is:
Specially for drawing thick line (line width > 1) you need a "pen". And
think of the tip of the pen as being a circle or en ellipse. So your
thick line is drawn by putting many ellipses one after another.

A long time ago I read in a documentation for the "old" GKS about an
optimization algorithm. Because you don't need to calculate the whole
ellipse for each step.

I hope, this explanation has some truth in it!

Greetings
Manfred





Bill Thoen schrieb:

> I'm trying to learn the MapServer lore and now I'm focusing on symbols. Can
> anyone tell me what the logic is where one is defining a _line_ style by
> using a TYPE of ELLIPSE (instead of LINE) and POINTS definition of one (x
> y) as in the symbol definition below? (This is from
> http://mapserver.gis.umn.edu/docs/reference/symbology/examples).
>
> SYMBOL
>   NAME 'dashed1'
>   TYPE ELLIPSE
>   POINTS 1 1 END
>   FILLED true
>   STYLE 10 5 5 10 END
> END
>
> I'm just curious. This seems like some historical artifact from the days
> when learning MapServer was hard. ;-)
>
> The TYPE ELLIPSE seems especially weird to me. Why not TYPE LINE?
>
> - Bill Thoen
>
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Re: Curious Symbol Structure

Steve Lime
In reply to this post by bthoen@gisnet.com
The type refers to the base type of the brush or marker you are creating
not
to the type of feature it is useful for. It's true in this case that
with the addition
of the style that this symbol is only really useful for lines, but you
could draw
markers with it or fill polygons in which case the dashing would be
ignored.

I think ideally we should pull the style, better called a pattern, out
into the
class style. That would eliminate this type of confusion...

Steve

>>> Bill Thoen <[hidden email]> 12/26/2006 7:42:59 PM >>>
I'm trying to learn the MapServer lore and now I'm focusing on symbols.
Can
anyone tell me what the logic is where one is defining a _line_ style
by
using a TYPE of ELLIPSE (instead of LINE) and POINTS definition of one
(x
y) as in the symbol definition below? (This is from
http://mapserver.gis.umn.edu/docs/reference/symbology/examples).

SYMBOL
  NAME 'dashed1'
  TYPE ELLIPSE
  POINTS 1 1 END
  FILLED true
  STYLE 10 5 5 10 END
END

I'm just curious. This seems like some historical artifact from the
days
when learning MapServer was hard. ;-)

The TYPE ELLIPSE seems especially weird to me. Why not TYPE LINE?

- Bill Thoen
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Re: Curious Symbol Structure

bthoen@gisnet.com
Steve Lime wrote:
> I think ideally we should pull the style, better called a pattern, out
> into the class style. That would eliminate this type of confusion...
>
> Steve
If you're thinking of changing things related to feature styles, you
might also want to look at the developing feature style standard for
OGR: http://ogr.maptools.org/ogr_feature_style.html.
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Re: Curious Symbol Structure

Eduardo Zenaide
In reply to this post by Steve Lime
a good link - i've found it yesterday :D

http://mapserver.gis.umn.edu/docs/howto/cartosymbols/#using-cartographic-symbols-in-umn-mapserver

2006/12/27, Steve Lime <[hidden email]>:
The type refers to the base type of the brush or marker you are creating
not
to the type of feature it is useful for. It's true in this case that
with the addition
of the style that this symbol is only really useful for lines, but you
could draw
markers with it or fill polygons in which case the dashing would be
ignored.

I think ideally we should pull the style, better called a pattern, out
into the
class style. That would eliminate this type of confusion...

Steve

>>> Bill Thoen <[hidden email]> 12/26/2006 7:42:59 PM >>>
I'm trying to learn the MapServer lore and now I'm focusing on symbols.
Can
anyone tell me what the logic is where one is defining a _line_ style
by
using a TYPE of ELLIPSE (instead of LINE) and POINTS definition of one
(x
y) as in the symbol definition below? (This is from
http://mapserver.gis.umn.edu/docs/reference/symbology/examples).

SYMBOL
  NAME 'dashed1'
  TYPE ELLIPSE
  POINTS 1 1 END
  FILLED true
  STYLE 10 5 5 10 END
END

I'm just curious. This seems like some historical artifact from the
days
when learning MapServer was hard. ;-)

The TYPE ELLIPSE seems especially weird to me. Why not TYPE LINE?

- Bill Thoen



--
Eduardo Zenaide