[mapserver-users] GEOMTRANSFORM LABELPNT example

[Brent Fraser]

Ian,

   No, there is no ability to do that, unless you use POSITION CC.  
There had been some discussion several months ago to add functions to 
the GEOMTRANSFORM resulting in RFC 72 
(http://www.mapserver.org/development/rfc/ms-rfc-72.html)

I think something like

GEOMTRANSFORM (getCentroid(labelpoly))

would be a good addition, but I don't have a specific use-case.  What 
were you planning to do the center of the label polygon?

Best Regards,
Brent Fraser


On 12/11/2011 2:18 PM, Ian Walberg wrote:
> So is it expected that labelpnt generates a point with its center at the middle of the bounding rectangle of the text?
>
> Thanks
>
> Ian
>
>
> -----Original Message-----
> From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Brent Fraser
> Sent: Sunday, December 11, 2011 1:02 PM
> To: thomas bonfort
> Cc: mapserver-users at lists.osgeo.org
> Subject: Re: [mapserver-users] GEOMTRANSFORM LABELPNT example
>
> Thomas,
>
>    I tracked it down to the LABELCACHE setting.
>
> LABELCACHE ON  gives the expected results LABELCACHE OFF  gives my old blue-dot-on-the-left results.
>
> See attached PDFs.
>
> Best Regards,
> Brent Fraser
>
>
> On 12/11/2011 1:05 PM, thomas bonfort wrote:
>> There might have been a bug in the initial implementation. trying it
>> out with current trunk gives me the expected result, unless I'm
>> missing something.
>>
>>
>> On Sun, Dec 11, 2011 at 20:44, Brent Fraser<bfraser at geoanalytic.com>   wrote:
>>> Thomas,
>>>    See comments below.
>>>
>>> Best Regards,
>>> Brent Fraser
>>>
>>>
>>>
>>> On 12/11/2011 12:26 PM, thomas bonfort wrote:
>>>> I think this is all expected behavior, although the documentation
>>>> may be incorrect.
>>>>
>>>> LABELPNT draws a marker on the geographic position the label is
>>>> attached to. This corresponds to the center of the label text only
>>>> if the label is in position CC.
>>> I think that is what is intended but my original test case (using CC
>>> ) resulted in the LABELPNT rendered on the left side of the
>>> labelpoly, see http://lists.osgeo.org/pipermail/mapserver-dev/attachments/20110526/47c9bc8c/labelpnt-0001.png.
>>>     I had expected it to be coincident with the yellow circle and green cross.
>>>
>>>
>>>> To draw a label at the center of the label text, another
>>>> geomtransform would have to be implemented, named e.g. LABELBBOXCENTROID.
>>> or maybe
>>>
>>> GEOMTRANSFORM (centroid([LABELPOLY]))
>>>
>>>
>>>> regards,
>>>> thomas
>>>>
>>>> On Sun, Dec 11, 2011 at 19:34, Brent Fraser<bfraser at geoanalytic.com>
>>>>    wrote:
>>>>> Hey Jeff,
>>>>>
>>>>>    I've been looking into this too (not finished yet).  I'm using
>>>>> v6.0.1 and can reproduce my original results (blue dot to the left)
>>>>> AND Ian's (grey dot coincident with white dot).  Very strange.  My
>>>>> shapefile dataset gets reprojected from geographic to UTM, so that
>>>>> may be causing the difference.
>>>>>    I need to look into that...
>>>>>
>>>>> Best Regards,
>>>>> Brent Fraser
>>>>>
>>>>>
>>>>>
>>>>> On 12/11/2011 10:57 AM, Jeff McKenna wrote:
>>>>>> On 11-12-11 11:20 AM, Ian Walberg wrote:
>>>>>>> Here is the map file we are using ms4w 3.0.3.
>>>>>>>
>>>>>>> We thought the larger grey circle should be drawn in the center
>>>>>>> of the label text.
>>>>>>>
>>>>>>> What have we done wrong?
>>>>>>>
>>>>>>>
>>>>>> I have done some testing on this on Windows, with MapServer trunk
>>>>>> (6.1-dev), here are my findings:
>>>>>>
>>>>>> - I used Brent's original example styles (from
>>>>>>
>>>>>> http://osgeo-org.1803224.n2.nabble.com/GEOMTRANSFORM-labelpnt-location-td6408065.html)
>>>>>> with Ian's FEATURE layer -->     Brent's "Blue Dot" LABELPNT with POSITION
>>>>>> CC is
>>>>>> now correctly placed in the center of the label text (so it seems
>>>>>> this has been fixed in the code, but I can't find the ticket that
>>>>>> says that)
>>>>>> - If I change to POSITION LR (as in Ian's example layer) then I
>>>>>> get Ian's issue (LABELPNT is placed at the geometry location, not
>>>>>> in the center of the label text
>>>>>> - but this is now an issue of understanding the developer's logic
>>>>>> (from that thread SteveL says "Let me ponder this and get back to
>>>>>> you. I think it makes sense to use the label point geotransform
>>>>>> only with position CC so that it matches actual shape location.")
>>>>>>
>>>>>> That's all I know at this point (ha pun).
>>>>>>
>>>>>> -jeff
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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