Thomas,
Yes, I've been trying to come up with good map file syntax to
indicate labeling of the transformed geometry. Currently mapserver allows:
- transformed original geometry (buffer, difference)
- augmented original geometry (bbox, start/end, vertices)
- rendered label geometry (labelpoint, labelpoly)
but it doesn't label transformed geometry, only original geometry. The
main problem (from a user interface perspective) is how to relate
transformed geometry to the label specification.
One solution is to allow a LABEL object within a STYLE object:
CLASS
NAME 'Streams'
STYLE
GEOMTRANSFORM (buffer([shape], 5))
LABEL
usual label settings
END # Label
END # Style
but that's a little strange as STYLE objects are currently allowed
within LABEL objects.
Another solution is to have "named" geometry and reference it in the
LABEL object (and keep the existing CLASS/STYLE/LABEL structure):
CLASS
NAME 'Streams'
STYLE
GEOMTRANSFORM my_label_shape = (buffer([shape], 5))
END # Style
LABEL
usual label settings
GEOMETRY my_label_shape
END # Label
And I'm sure there are other (and hopefully better) solutions.
Best Regards,
Brent Fraser
On 6/6/2011 11:02 AM, thomas bonfort wrote:
Yes, the resulting shape seems like a nice candidate for offseting
labels, but the problem with buffer is you will have more difficulty
in deciding what is to the left from what is to the right of the line.
We'd also have to make sure that the buffer operation is not too
costly on cpu cycles.
Anyways, until geomtransform is not applied at the layer level, there
is no way to use this method as the label does not operate on the
transformed geometry.
On Mon, Jun 6, 2011 at 17:30, Brent Fraser<bfra...@geoanalytic.com> wrote:
Steve,
I think just buffering the line would apply a type of smoothing (see
attached image). Using the resulting buffer line (or perhaps doing some
simple line smoothing on it) for labeling would be good enough.
Best Regards,
Brent Fraser
On 6/6/2011 9:04 AM, Stephen Woodbridge wrote:
Duh! you are correct, I always forget this point until I after my second
cup of coffee has kicked in :)
That article looks very interesting, I have to read up on that.
In a past career in computer aided design and manufacturing, we used the
idea of a rolling ball offset because it modeled a milling machine. The
rolling ball offset is defined as the curve traced by the center of a ball
of a given radius as you roll it along a curve. The circumference of the
ball can not cross over the original curve so for tight "S" curves if the
diameter of the ball is larger than the gap in the "S" then the ball does
not enter the gap but floats over it. This same concept would make for well
behaved and good looking labels along tight twisty paths like rivers and
roads.
Another idea for smoothing out curves for labeling might be to apply an N
point moving average and allow that to be the label path. I don't think this
has been mentioned as an option in the past.
-Steve W
On 6/6/2011 10:20 AM, thomas bonfort wrote:
There are two problems with the solution you propose:
- if you offset the geometry in postgis, the distance of the offset
will be in geographical units, i.e. it will not give correct results
at all scales when rendered with mapserver (what you basically want is
to offset the line by a number of pixels roughly equal to the size of
the font used for labelling)
- angle follow on offset line should probably be done on a
simplified/smoothed geometry. see
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.24.6970 .
Ideally someone will want the feature badly enough to fund it :)
--
thomas
On Mon, Jun 6, 2011 at 16:02, Stephen Woodbridge
<wood...@swoodbridge.com> wrote:
There was some recent discussion on the dev list about potentially using
the
GEOMTRANSFORM to do something like a single sided offset then using that
to
apply the label to. BUT I do not think that has been implemented yet in
mapserver.
Google for "mapserver geomtransform" also look at "geoprocessing" for
some
other ideas.
Anyway, you might be able to do what you want if you:
1. import your data into PostGIS
2. create offset geometry in another table
3. export that table to a shapefile
4. then label that as an annotation layer so you do not draw the
geometry
only the label and use the original data to draw the grometry ie: two
layers.
I have not tried this, but it might solve your problem.
-Steve W
On 6/6/2011 9:48 AM, uvg wrote:
Thank you, Thomas.
Are there any workarounds for this problem?
Is there 'best practices' for the problem?
Maybe unvisible layer or other?
06.06.2011, 17:35, "thomas bonfort [via OSGeo.org]"<[hidden email]
</user/SendEmail.jtp?type=node&node=6445194&i=0>>:
The status has not changed: label follow with offset is not
supported.
regards,
thomas
On Mon, Jun 6, 2011 at 15:33, uvg<[hidden email]> wrote:
Hi all!
Sorry for my bad English.
I am trying to achieve is a label that follows the rivers that is
also
OFFSET so that
the label does not 'above' on the line for the river.
Sample code of mapfile:
LABEL
COLOR 0 40 255
FONT "arial-italic"
TYPE truetype
SIZE 7
OFFSET 5 0
ANGLE FOLLOW
POSITION LC
FORCE true
PARTIALS FALSE
END
"OFFSET" does not work.
How can I offset a label?
I found a message posted for a long time:
click here.
View this message in context: Re: ANGLE FOLLOW and Label Offset (v.
5.6.6)
<http://osgeo-org.1803224.n2.nabble.com/ANGLE-FOLLOW-and-Label-Offset-v-5-6-6-tp6445138p6445194.html>
Sent from the Mapserver - User mailing list archive
<http://osgeo-org.1803224.n2.nabble.com/Mapserver-User-f1969211.html>
at
Nabble.com.
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