[mapserver-users] Offset values from database

Fri Aug 13 13:55:45 EDT 2010

I would like to shade the inside of a polygon along it's border.  Using
the polygon border as the edge.  Making wider lines means offsetting the
poygon internally or putting up with the edge not being specifically
accurate. 

bobb 

>>> Wim Vanbelle <wimvanbelle at gmail.com> wrote:

Would it not be possible to draw the polygon as 2 different polygons
(the inner polygon & the outer using the postgis functions)? You could
specify a fixed offset for one or the other.

On the other hand, if you just have 1 polygon (with a single line, so no
inner polygons) and you're trying to accomplish a visual effect that the
inside of the polygon lies further away, i would accomplish this by
drawing a thicker border.

Or you could possibly use the asymmetric line drawing functions that are
available.

Maybe give a more concrete example of what exactly you are trying to do.

On 12 August 2010 22:46, Bob Basques 
<Bob.Basques at ci.stpaul.mn.us> 

wrote:

All, 

Wondering, would this work for INSIDE/OUTSIDE situations with regard to
polygon drawing? Or is the left/right sides of the line strictly relying
on the from/to aspects of how the polygon was drawn
(clockwise/counterclockwise) This would be handy for off-setting to
(ONLY) the inside of a polygon for example. 

Thanks 

bobb 

>>> Wim Vanbelle <wimvanbelle at gmail.com> wrote:

Thank you very much everyone. And especially Thomas. That was indeed
what I was looking for. You saved me a lot of work!

Much appreciated.

On 12 August 2010 17:50, Fawcett, David (MPCA) 
<David.Fawcett at state.mn.us> 

wrote:

Thanks Thomas

That looks nice in my test example.

David.

-----Original Message-----
From: thomas bonfort [mailto:thomas.bonfort at gmail.com]
Sent: Thursday, August 12, 2010 10:45 AM
To: Fawcett, David (MPCA)
Cc: Wim Vanbelle; mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] Offset values from database

the -99 is a special offset value that shifts the line as you are
looking for.

style
color 255 0 0
offset -2 -99
width 2
end
style
color 0 255 0
offset 2 -99
width 2
end

not perfect as there are artifacts on sharp angles, but worth a try.

regards,
thomas

On Thu, Aug 12, 2010 at 16:56, Fawcett, David (MPCA)
<David.Fawcett at state.mn.us> wrote:
> Wim,
>
>
>
> You can do these offsets in pixel values at a class level, just not a
> feature level. This pretty much does what you are describing, although
it
> gets a little funky when the lines are diagonal and not straight.
>
>
>
> CLASS
>
> STYLE
>
> COLOR 0 0 0
>
> WIDTH 2
>
> END
>
> STYLE
>
> COLOR 255 0 0
>
> WIDTH 2
>
> OFFSET 10 10
>
> END
>
> STYLE
>
> COLOR 0 255 0
>
> WIDTH 2
>
> OFFSET -10 -10
>
> END
>
>
>
> END
>
>
>
> David.
>
>
>
> From: mapserver-users-bounces at lists.osgeo.org
> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Wim
Vanbelle
> Sent: Thursday, August 12, 2010 9:32 AM
> To: mapserver-users at lists.osgeo.org
> Subject: Re: [mapserver-users] Offset values from database
>
>
>
> Maybe this pic helps elaborate on what i'm trying to accomplish:
> http://fileshare.myroute.be/exchange/asymmetriclinedrawing.png
> It should be noted that the distance between the 2 (new) lines, should
be a
> fixed value over the zoomlevels. It must not be the case that at the
> furthest zoomlevel the lines are further apart.
>
> I've looked all over for this, but never really found a proper
solution. I
> tried cartographic symbol drawing, but it only draws on the same side
every
> time. Maybe I'm just doing it wrong :).
>
> On 12 August 2010 16:28, Wim Vanbelle <wimvanbelle at gmail.com> wrote:
>
> Hello,
>
> thanks for your feedback.
>
> The issue with this, is that the underlying linestrings (the 2 that
would
> lie on top of eachother), have different colors :(.
>
> So they have to be moved apart from one another. I have not found a
way to
> do this with asymmetric line drawing either, 
as it will always offset
to the
> would always appear next to eachtoher (no matter what zoomlevel).
>
> I can elaborate on the problem more if I am a little too confusing !
>
> On 12 August 2010 16:20, Cristiano Sumariva <sumariva at gmail.com>
wrote:
>
> If it is a display problem why not try create some special symbology
to
> overlap one line with another using different symbol strokes. So the
user
> will se that are 2 lines overlayed.
>
> 2010/8/12 Wim Vanbelle <wimvanbelle at gmail.com>
>
> Hi David,
>
> I read that documentation before though. I was hoping it just hadn't
been
> updated... Is this possibly a feature for 6.0 ?
>
> Are there any other ways how one could offset a feature in pixels,
rather
> than in lat/long coords?
>
> Maybe I should elaborate on the original problem a little. Consider 2
line
> segments that lie above one another. The general idea is to 'offset'
them a
> given x , y value, so they will both display next to one another,
rather
> than on top of eachother.
>
> If you would however perform this code simply on lat/long values, it
would
> imply, that when scaling your map at the most detailed zoom level, the
lines
> would lie very far apart, and when zoomed out, they would appear to
lie on
> top of eachother.
>
> I find it hard to believe that I would need to pre calculate all the
data in
> order to obtain geometry objects for each zoom level.
>
> Maybe some veterans have some good insight in this :).
>
>
>
> On 12 August 2010 15:26, Fawcett, David (MPCA)
<David.Fawcett at state.mn.us>
> wrote:
>
> Wim,
>
>
>
> If you don’t want me to tell you, you will likely want to look at the
> mapfile documentation at: http://mapserver.org/mapfile/style.html
>
>
>
> [Spoiler Alert]
>
> You can’t use values from an attribute table to set the value of this
> property
>
> [/Spoiler Alert]
>
>
>
> David.
>
> From: mapserver-users-bounces at lists.osgeo.org
> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Wim
Vanbelle
> Sent: Thursday, August 12, 2010 5:48 AM
>
> To: mapserver-users at lists.osgeo.org
>
> Subject: [mapserver-users] Offset values from database
>
>
>
> Hi,
>
> I'm trying to load offset X, Y data from the postgis database.
>
> Each feature has an offset value defined there.
>
> My mapfile (relevant part) looks like this:
>
> In the layer:
> DATA "geom_mercator from map_links using
> unique Id using SRID=900913"
>
> STYLE
> WIDTH 6
> COLOR 0 255 0
> ANTIALIAS TRUE
> ANGLE AUTO
> OFFSET [offsetX] [offsetY]
> END
>
> Please don't tell me the offsetX, Y values cannot be read from the
database.
> That would be a huge issue for me.
>
> Thank you for your time.
>
> Best regards
>
>
>
>
>
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