[mapserver-users] GEOMTRANSFORM LABELPNT example

[Stephen Woodbridge]

It seems to me that we should develop specific use cases that we are 
trying to support.

We have one that this feature was developed for, and that is as Steve L 
mention for labeling Highway Shields were the actual shield may be 
composed of multiple parts that need to be be super imposed relative to 
a label point, if I recall the details of that discussion without 
looking it up again.

Ian, I think the point you are looking for is different. That would be 
the centroid of the label polygon. That point may or may not be 
coincidentally the same as the LABELPNT under some small set of 
configuration parameters but by no means guaranteed to be the same.

I think that these points might be the same is you have a single line of 
text, ie: not wrapped, and POSITION CC and probable ANGLE 0. But I have 
not had time to test.

-Steve W

On 12/11/2011 4:18 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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