OpenCV: Update to 2.3.1a

Also correct `PYTHONPATH` in caveats.

Fixes Homebrew/homebrew#5596.

Fixes Homebrew/homebrew#7121.
Fixes Homebrew/homebrew#7453.

Closes Homebrew/homebrew#6692.
Closes Homebrew/homebrew#7500.
Closes Homebrew/homebrew#7706.

Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>

Formula/opencv.rb

@@ -1,10 +1,18 @@
 require 'formula'
 
+def which_python
+  "python" + `python -c 'import sys;print(sys.version[:3])'`.strip
+end
+
+def site_package_dir
+  "lib/#{which_python}/site-packages"
+end
+
 class Opencv < Formula
-  url 'http://downloads.sourceforge.net/project/opencvlibrary/opencv-unix/2.2/OpenCV-2.2.0.tar.bz2'
-  version "2.2"
+  url 'http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.3.1/OpenCV-2.3.1a.tar.bz2'
+  md5 '82e4b6bfa349777233eea09b075e931e'
   homepage 'http://opencv.willowgarage.com/wiki/'
-  md5 '122c9ac793a46854ef2819fedbbd6b1b'
+
 
   depends_on 'cmake' => :build
   depends_on 'pkg-config' => :build
@@ -17,6 +25,12 @@ class Opencv < Formula
   # you don't need unless you're doing video analysis, and some of it isn't
   # in Homebrew anyway.
 
+  def patches
+    # Fix conflict when OpenEXR is installed. See:
+    #   http://tech.groups.yahoo.com/group/OpenCV/message/83201
+    DATA
+  end
+
   def options
     [['--build32', 'Force a 32-bit build.']]
   end
@@ -31,9 +45,27 @@ class Opencv < Formula
 
   def caveats; <<-EOS.undent
     The OpenCV Python module will not work until you edit your PYTHONPATH like so:
-      export PYTHONPATH="#{HOMEBREW_PREFIX}/lib/python2.6/site-packages/:$PYTHONPATH"
+      export PYTHONPATH="#{HOMEBREW_PREFIX}/#{site_package_dir}:$PYTHONPATH"
 
     To make this permanent, put it in your shell's profile (e.g. ~/.profile).
     EOS
   end
 end
+
+__END__
+
+Fix conflict when OpenEXR is installed. See:
+  http://tech.groups.yahoo.com/group/OpenCV/message/83201
+
+diff --git a/modules/highgui/src/grfmt_exr.hpp b/modules/highgui/src/grfmt_exr.hpp
+index 642000b..b1414f1 100644
+--- a/modules/highgui/src/grfmt_exr.hpp
++++ b/modules/highgui/src/grfmt_exr.hpp
+@@ -56,6 +56,7 @@ namespace cv
+ 
+ using namespace Imf;
+ using namespace Imath;
++using Imf::PixelType;
+ 
+ /* libpng version only */
+