[mapserver-users] Still impossible to force labels inside their polygons?

Tue Sep 4 13:20:30 PDT 2012

Jukka,

If you look at RFC 81, it is likely that using this placement algorithm 
with leader lines would also work well with these kinds of parcels. It 
would be interesting to see how they determine the font size. It looks 
like it might be based on a function of the horizontal width of the 
polygon at the label point. It is not clear to me how they compute the 
label point based on these images. I think they use the leader lines if 
the horizontal width of the polygon at the label point is less than some 
%age of the label length.

I just updated this ticket.
https://github.com/mapserver/mapserver/issues/3948

You guys might want to watch this ticket also and add any additional 
comments to this ticket so that they are all captured in one place.

Thanks,
-Steve W

On 9/4/2012 2:59 PM, Rahkonen Jukka wrote:
> Hi,
>
> The polygons in the data are cadastrial parcels and user wants that
> each parcel could be identified right. GetFeatureInfo is not enough
> because he wants also printed maps. Therefore each parcel should have
> a label that is readable in some scale. That is not always easy
> because the size of parcels varies a lot.
>
> Here is a reference implementation by the National Land Survey of
> Finland:
> http://www.paikkatietoikkuna.fi/web/fi/kartta?zoomLevel=10&coord=271051.5_6947937&mapLayers=base_35+100+!default!,90+100+,99+100+&showMarker=false&forceCache=true
>
>  NLS has decided to use vertical labels with variable font size for
> keeping the label text usually inside their polygons. Sometimes there
> seems to be also leader lines. The result is rather readable but I
> believe that labels have at least partly set by hand.  In the NLS
> service the labels comes from a readily rasterised layer and they are
> shown only on three highest zoom levels.
>
> Here is another place with very long and narrow parcels. The NLS
> labeling system does not suit here very well for web browsing because
> labels are often in a fixed place outside the map window.
> http://www.paikkatietoikkuna.fi/web/fi/kartta?zoomLevel=10&coord=227539.5_6999494&mapLayers=base_35+100+!default!,90+100+,99+100+&showMarker=false&forceCache=true
>
>
>
> -Jukka-
>
> Stephen Woodbridge wrote:
>
>> Jukka,
>
>> Based on your sample image you probably want something like ANGLE
>> AUTO
> on a polygon to try to compute the longest line that you can insert
> into the polygon and then label along that. That would do two things,
> compute an ideal label point and whatever angle you need to position
> the text.
>
>> But no this does not exist in mapserver. There are a bunch of
>> label
> enhancement tickets and a lot of work has been done recently in this
> area. You could add some of this thread to an appropriate ticket or
> open a new one if there isn't already one.
>
>> 6.2 also have offset labels with leaders. In this case it creates
>> a
> label and draws an arrow to point at the feature. Thomas posted some
> examples to the list at some point. See:
> http://mapserver.org/development/rfc/ms-rfc-81.html and google:
> mapserver offset labels rfc81
>
>> I do have a ticket open for labeling a polygon along an interior
>> or
> exterior edge. The idea being that I want to label country borders.
> I want the label to FOLLOW the border, but it needs to be offset
> either inside or outside the polygon. If this were implemented then
> it would work for your case if you could live with the label inside
> and along an edge. But it has not been implemented yet.
>
> -Steve W
>
> On 9/4/2012 11:13 AM, Lime, Steve D (DNR) wrote:
>> It's tough to know what I'm looking at from the picture. What does
>> the layer definition look like?
>>
>> At the moment polygon label point computation tries a couple of
>> approaches get a label point inside the polygon: 1) compute a
>> center of gravity 2) if that computation doesn't work (e.g. point
>> is too close to the edge) then a scanline-based process is used to
>> sample possible positions. The mid-point of the longest y sample is
>> used.
>>
>> It's always trade-off with speed and the above seems a happy
>> medium.
>>
>> Steve
>>
>> -----Original Message----- From:
>> mapserver-users-bounces at lists.osgeo.org
>> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of
>> Rahkonen Jukka Sent: Tuesday, September 04, 2012 9:48 AM To:
>> 'Mapserver-Users (mapserver-users at lists.osgeo.org)' Subject: Re:
>> [mapserver-users] Still impossible to force labels inside their
>> polygons?
>>
>> Hi,
>>
>> Thank you for the answer. A little screenshot shows an example
>> with two label points  inside one polygon and one polygon without a
>> label point at all. Perhaps we could have more accurate polygon
>> label positioning on our wish list.
>>
>> -Jukka Rahkonen-
>>
>>
>> Lime, Steve D (DNR) wrote:
>>
>>> Aihe: RE: [mapserver-users] Still impossible to force labels
>>> inside their polygons?
>>>
>>> Yes, still impossible. POSITION CC + MINFEATURESIZE AUTO will
>>> get you close. However, MINFEATURESIZE AUTO uses bounding box
>>> checks and doesn't intersect a feature geometry with its label
>>> geometry.
>>>
>>> Steve
>>>
>>> -----Original Message----- From:
>>> mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-
>>> bounces at lists.osgeo.org] On Behalf Of Rahkonen Jukka Sent:
>>> Tuesday, September 04, 2012 9:17 AM To: 'Mapserver-Users
>>> (mapserver-users at lists.osgeo.org)' Subject: [mapserver-users]
>>> Still impossible to force labels inside their polygons?
>>>
>>> Hi,
>>>
>>> Is the short answer by Stephen Woodbridge "No" in the tread
>>> http://osgeo-
>>> org.1560.n6.nabble.com/force-labels-to-fit-in-polygons-td4549296.html
>>>
>>>
>
>>>
still valid?
>>>
>>> I have been trying to label a polygon dataset with Mapserver 6.2
>>> beta2 and some labels keep on falling outside their polygons.
>>> By the way, the thread contains an advice that does not work for
>>> me: " By the way, PROCESSING "LABEL_NO_CLIP=ON" will fix the
>>> label point at the polygon center. -SteveW "
>>>
>>> Is the solution to create a new layer with point-on-surface
>>> function and label then this point layer?
>>>
>>> -Jukka Rahkonen- _______________________________________________
>>> mapserver-users mailing list mapserver-users at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>
>>
>>
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