Label are occassional upside down

[woodbri@…]

I am getting occassional labels that are upside down. This feels like a corner 
case that is not be checked properly. I looked at the code but it was not clear 
to me how the angle was be detected and flipped if it was upside down.

Here is the software that I'm running on debian stable Woody:

curl-7.11.0          freetype-2.1.5.tar.gz   owt-20031104.tar.gz
curl-7.11.0.tar.gz   gd-2.0.21               php-4.3.4
doit-all             gd-2.0.21.tar.gz        php-4.3.4.tar.gz
doit-mapserver       gdal-1.1.9              proj-4.4.7
doit-php             gdal-1.1.9.tar.gz       proj-4.4.7.tar.gz
expat-1.95.7         mapserver-4.0.1         shapelib-1.2.10
expat-1.95.7.tar.gz  mapserver-4.0.1.tar.gz  shapelib-1.2.10.tar.gz
freetype-2.1.5       owt-20031104

it is compiled using the following options:

swoodbridge@maps5:/u/software$ cat doit-all
#
# first untar the source archives

for X in *.gz ; do tar xzf $X ; done

# make sure we have the required system packages

# required by gd-2
sudo apt-get install libpng libpng-dev
sudo apt-get install libjpeg62 libjpeg62-dev

# required by php4
sudo apt-get install libmysqlclient10-dev

# required by owt
sudo apt-get install libttf-dev libttf2

# For  curl-7.11.0.tar.gz
(
  cd curl-7.11.0
  ./configure --prefix=/opt/mapserver/
  make
  sudo make install
)
# For  freetype-2.1.5.tar.gz
(
  cd freetype-2.1.5
  ./configure --prefix=/opt/mapserver/
  make
  sudo make install
)
# For  gd-2.0.21.tar.gz
(
  cd gd-2.0.21
  ./configure --prefix=/opt/mapserver/ --with-freetype=/opt/mapserver/
  make
  sudo make install
)
# For  gdal-1.1.9.tar.gz
(
  cd gdal-1.1.9
  ./configure --prefix=/opt/mapserver/ --with-ogr --without-gif
  make
  sudo make install
)
# For  proj-4.4.7.tar.gz
(
  cd proj-4.4.7
  ./configure --prefix=/opt/mapserver/
  make
  sudo make install
)
# For  expat-1.95.7.tar.gz
(
  cd expat-1.95.7
  ./configure --prefix=/opt/mapserver/
  make
  sudo make install
)
# For  php-4.3.4.tar.gz
(
  cd php-4.3.4
  ./configure \
    --enable-dbase \
    --enable-force-cgi-redirect \
    --with-config-file-path=/opt/mapserver/php4 \
    --with-regex=system \
    --with-gd=/opt/mapserver \
    --with-ttf=/opt/mapserver \
    --enable-gd-native-ttf \
    --with-freetype-dir=/opt/mapserver \
    --without-xpm \
    --with-mysql=/usr
  make
  sudo make install
  sudo mkdir -p /opt/mapserver/php4/extensions
  sudo sapi/cgi/php /opt/mapserver/php4/
  sudo cp php.ini-recommended /opt/mapserver/php4/php.ini
  #--------------------------------------------------
  echo "You need to edit /opt/mapserver/php4/php.ini"
  echo " and setup the session handling for chameleon"
  #--------------------------------------------------
  
)
# For  mapserver-4.0.1.tar.gz
(
  cd mapserver-4.0.1

#------------------------------------------------------
echo "You need to edit map.h and change MS_MAXLAYERS to 175"
echo "and then comment out the exit command on the next line"
exit;
#------------------------------------------------------
  
  ./configure \
    --with-httpd=/usr/sbin/apache \
    --with-proj=/opt/mapserver \
    --with-wmsclient \
    --with-gd=/opt/mapserver \
    --with-freetype=/opt/mapserver \
    --with-gdal \
    --with-ogr=/opt/mapserver/bin/gdal-config \
    --with-php=../php-4.3.4 \
    --without-tiff \
    --enable-runpath \
    --without-xpm \
    --with-curl-config=/opt/mapserver/bin/curl-config
  make
  sudo mkdir /opt/mapserver/cgi-bin
  sudo cp mapserv scalebar legend /opt/mapserver/cgi-bin/
  sudo cp mapscript/php3/php_mapscript.so /opt/mapserver/php4/extensions/
)
# For  owt.tar.gz
(
  cd owt-20031104
  make
  sudo cp owtchart/owtchart /opt/mapserver/cgi-bin/
)
# For  shapelib-1.2.10.tar.gz
(
  cd shapelib-1.2.10
)
swoodbridge@maps5:/u/software$

[woodbri@…]

railroad-label-upside-down

[woodbri@…]

I just downloaded Mapserver 4.4.1 and con confirm that this bug still exists. I
know you would like a test case, but I think it would be very hard to extract
the data to a separate set of shapefiles. I can reproduce this easily and
reliably on a map that is not very detailed like this one
http://data.dev.where2getit.com/cgi-bin/mapserv?mode=map&layers=all&scale=25000&map=/home/direct/mapserver/default_mapfile.map&mapxy=-71.38918+42.61935&map_size=300+200

[woodbri@…]

OK, I have made a trivial example that reproduces this problem
http://data.dev.where2getit.com/cgi-bin/mapserv?mode=map&layers=all&map=/u/work/swoodbridge/angles/angles.map&mapxy=0+0&mapsize=800+800

I will attach a tarball with a shapefile and mapfile. I seems that this problem
may be related to POSITION AUTO because when I use POSITION CC all the labels
look OK, but that might be just a side effect that masks the real issue.

[woodbri@…]

Tar file with shapefile and mapfile to reproduct upside down labels.

[dmorissette]

Now that we have a test case let's see if we can get it fixed for 4.6. I'll at
least see if I can reproduce at my end.

[dmorissette]

I found the issue and think I fixed it, it was an angle passed to the cos()
function in degrees instead of radians.

Unfortunately I'm unable to commit to CVS at the moment due to a lock problem on
the CVS server. You can try the following patch to confirm that it works for ou
and then I'll backport to 4.4.


diff -u -r1.98 mapgd.c
--- mapgd.c     28 Feb 2005 14:17:49 -0000      1.98
+++ mapgd.c     20 Apr 2005 19:39:30 -0000
@@ -2869,7 +2869,7 @@
          cachePtr->status = MS_TRUE; /* assume label *can* be drawn */
  
          if(j == 1) {
-           if(fabs(cos(labelPtr->angle)) < LINE_VERT_THRESHOLD)
+           if(fabs(cos(labelPtr->angle*MS_DEG_TO_RAD)) < LINE_VERT_THRESHOLD)
              labelPtr->angle += 180.0;
            else
              position = MS_LC;

[dmorissette]

Fixes committed to 4.5 CVS. Steve W, can you please test and confirm that the
fix works for all your testcases and then I'll backport to 4.4.

[woodbri@…]

Daniel, 

This looks much better, but there may be another problem. The labels on angles
81-89 look like they are flipped. Change the mapfile to "POSITION CC" instead of
"POSITION AUTO" and all these labels will flip. I would expect the same
orientation of labels regardless of POSITION setting. I have not checked any of
the other POSITION values to see what they look like.

I backported the patch to MS 4.4.1 and did my testing there.

[dmorissette]

Good Catch. That's because of the following test in msDrawLabelCacheGD():

	  if(j == 1) {
	    if(fabs(cos(labelPtr->angle*MS_DEG_TO_RAD)) < LINE_VERT_THRESHOLD)
	      labelPtr->angle += 180.0;
	    else
	      position = MS_LC;
	  }

This test never really worked before because of the missing MS_DEG_TO_RAD that I
added yesterday, but now that it's working, it seems that it flips any label
between 81 and 90 degrees. 

LINE_VERT_THRESHOLD is defined as 0.17, and arccos(0.17) = 80.2, that's why you
now see all labels between 81 and 89 degrees flipped.

Unfortunately I have no clue what this test is for or what it's trying to do
exactly. I'll have to reassign to Steve Lime since I presume he is the author of
this code.

[sdlime]

Man, now you're really testing my memory. The test is there to deal with nearly 
vertical lines, but I'll have to think about it and run a few test cases I've 
got squirreled away to recall why I added it. If things were busted because of 
the missing conversion perhaps that is why it was added in the first place. 
I'll look though...

Steve

[sdlime]

I played with that code and Steve's example (great one by the way, need to hold
onto that for any font testing) and really couldn't recreate my train of thought
on that test. So, I removed the test and the angle output looks good. I noticed
that Assefa is using that same test within the pdf|svg|swf sources and it should
be removed there as well, and then the LINE_VERT_THRESHOLD should be removed
from maplabel.c. CC'ing Assefa to make sure that's ok to do. I'll make the
changes once ok'd. Will post the angle output image next...

Steve

Steve W. - Thanks for your persistance on this one. Wish I would have had your
sample shapefile during development. I only had a 20 line shapefile which missed
the problem angles.

[sdlime]

Post-fix angle image.

[sdlime]

Didn't hear any objections so I pulled that LINE_VERT... test from the
SWF/PDF/SVG and imagemap drivers. Calling this one closed.

Steve

[dmorissette]

Thanks Steve.