[mapserver-users] Offset values from database

[Wim Vanbelle]

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
>> > same side.
>> >
>> > This is why i would need the offset value to be configurable in the
>> > database. I could select a different pixel offset for each line and they
>> > 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
>> >
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > mapserver-users mailing list
>> >
>> > mapserver-users at lists.osgeo.org
>> >
>> > http://lists.osgeo.org/mailman/listinfo/mapserver-users
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > _______________________________________________
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>> > http://lists.osgeo.org/mailman/listinfo/mapserver-users
>> >
>> >
>>
>>
>
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