[mapserver-users] GEOMTRANSFORM LABELPNT example

Sun Dec 11 17:06:09 EST 2011

Brent,

Ok, we had been using an earlier version of the mapserver documentation
we had downloaded which had the text below.

The latest version now describes the discussed functionally more
closely.

We had been looking at using the previous functionally to draw and
rotate a symbol around the label text. Not what we are thinking but this
could be used for something like displaying the wind speed and symbol
rotated for the wind direction using a symbol around the outside.

To do this it sounds like a new GEOMTRANSFORM type.

Thanks

Ian

STYLE The start of a STYLE object.

Label specific mechanisms of the STYLE object are the GEOMTRANSFORM
options:

GEOMTRANSFORM [labelpnt|labelpoly] Creates geometries that can be used
for styling the label.

* labelpnt generates a point with its center at the middle of the
bounding rectangle of the text.

* labelpoly generates the bounding rectangle for the text, with 1 pixel
of padding added in all directions.

The resulting geometries can be styled using the mechanisms available in
the STYLE object.

New in version 6.0.

From: Brent Fraser [mailto:bfraser at geoanalytic.com] 
Sent: Sunday, December 11, 2011 1:52 PM
To: Ian Walberg
Cc: mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] GEOMTRANSFORM LABELPNT example

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> <mailto: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/20110526/47c9
bc8c/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> <mailto: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-t
d6408065.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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