From 44d1738d47567e6f80fc408cce0a574f4d5ca888 Mon Sep 17 00:00:00 2001
From: Maksim Shabunin <maksim.shabunin@itseez.com>
Date: Fri, 22 May 2015 17:55:08 +0300
Subject: [PATCH 1/2] Transition guide: how to check library version

---
 .../transition_guide.markdown                 | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/doc/tutorials/introduction/transition_guide/transition_guide.markdown b/doc/tutorials/introduction/transition_guide/transition_guide.markdown
index 5f3e35150c..6cf13172f5 100644
--- a/doc/tutorials/introduction/transition_guide/transition_guide.markdown
+++ b/doc/tutorials/introduction/transition_guide/transition_guide.markdown
@@ -257,3 +257,49 @@ _cuda_ module has been split into several smaller pieces:
 Documentation format {#tutorial_transition_docs}
 --------------------
 Documentation has been converted to Doxygen format. You can find updated documentation writing guide in _Tutorials_ section of _OpenCV_ reference documentation (@ref tutorial_documentation).
+
+Support both versions {#tutorial_transition_both}
+---------------------
+In some cases it is possible to support both versions of OpenCV.
+
+### Source code
+
+To check library major version one of the following methods can be used:
+- if __CV_VERSION_EPOCH__ is defined - you are using 2.4 branch, otherwise - 3.x
+- __CV_MAJOR_VERSION__ is defined as `2` or `3` for corresponding version
+
+One of `opencv2/core/version.hpp` or `opencv2/core/core.hpp` files should be included to use these definitions.
+
+Examples:
+@code{.cpp}
+#ifdef CV_VERSION_EPOCH
+// do opencv 2 code
+#else
+// do opencv 3 code
+#endif
+@endcode
+or
+@code{.cpp}
+#if CV_MAJOR_VERSION == 2
+// do opencv 2 code
+#elif CV_MAJOR_VERSION == 3
+// do opencv 3 code
+#endif
+@endcode
+@note Do not use __CV_VERSION_MAJOR__, it has different meaning for 2.4 and 3.x branches!
+
+### Build system
+
+It is possible to link different modules or enable/disable some of the features in your application by checking library version in the build system. Standard cmake or pkg-config variables can be used for this:
+- `OpenCV_VERSION` for cmake will contain full version: "2.4.11" or "3.0.0" for example
+- `OpenCV_VERSION_MAJOR` for cmake will contain only major version number: 2 or 3
+- pkg-config file has standard field `Version`
+
+Example:
+@code{.cmake}
+if(OpenCV_VERSION VERSION_LESS "3.0")
+# use 2.4 modules
+else()
+# use 3.x modules
+endif()
+@endcode

From 55d1f0b7d602bfde8bd1c3dc8419ef95c3ae606b Mon Sep 17 00:00:00 2001
From: Maksim Shabunin <maksim.shabunin@itseez.com>
Date: Mon, 25 May 2015 18:05:20 +0300
Subject: [PATCH 2/2] Transition guide: removed one of the version check
 methods

---
 .../transition_guide/transition_guide.markdown | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/doc/tutorials/introduction/transition_guide/transition_guide.markdown b/doc/tutorials/introduction/transition_guide/transition_guide.markdown
index 6cf13172f5..b0bc44344c 100644
--- a/doc/tutorials/introduction/transition_guide/transition_guide.markdown
+++ b/doc/tutorials/introduction/transition_guide/transition_guide.markdown
@@ -264,28 +264,16 @@ In some cases it is possible to support both versions of OpenCV.
 
 ### Source code
 
-To check library major version one of the following methods can be used:
-- if __CV_VERSION_EPOCH__ is defined - you are using 2.4 branch, otherwise - 3.x
-- __CV_MAJOR_VERSION__ is defined as `2` or `3` for corresponding version
-
-One of `opencv2/core/version.hpp` or `opencv2/core/core.hpp` files should be included to use these definitions.
-
-Examples:
-@code{.cpp}
-#ifdef CV_VERSION_EPOCH
-// do opencv 2 code
-#else
-// do opencv 3 code
-#endif
-@endcode
-or
+To check library major version in your application source code, the following method should be used:
 @code{.cpp}
+#include "opencv2/core/version.hpp"
 #if CV_MAJOR_VERSION == 2
 // do opencv 2 code
 #elif CV_MAJOR_VERSION == 3
 // do opencv 3 code
 #endif
 @endcode
+
 @note Do not use __CV_VERSION_MAJOR__, it has different meaning for 2.4 and 3.x branches!
 
 ### Build system