Manage Python Limited API version externally.

CMakeLists.txt

@@ -1866,6 +1866,7 @@ if(BUILD_opencv_python3)
   else()
     status("    Libraries:"   HAVE_opencv_python3  THEN  "${PYTHON3_LIBRARIES}"                                      ELSE NO)
   endif()
+  status("    Limited API:" PYTHON3_LIMITED_API THEN "YES (ver ${PYTHON3_LIMITED_API_VERSION})"                    ELSE NO)
   status("    numpy:"         PYTHON3_NUMPY_INCLUDE_DIRS THEN "${PYTHON3_NUMPY_INCLUDE_DIRS} (ver ${PYTHON3_NUMPY_VERSION})" ELSE "NO (Python3 wrappers can not be generated)")
   status("    install path:"  HAVE_opencv_python3  THEN "${__INSTALL_PATH_PYTHON3}"                            ELSE "-")
 endif()

cmake/OpenCVDetectPython.cmake

@@ -291,6 +291,12 @@ find_python("${OPENCV_PYTHON3_VERSION}" "${MIN_VER_PYTHON3}" PYTHON3_LIBRARY PYT
     PYTHON3_INCLUDE_DIR PYTHON3_INCLUDE_DIR2 PYTHON3_PACKAGES_PATH
     PYTHON3_NUMPY_INCLUDE_DIRS PYTHON3_NUMPY_VERSION)
 
+# Problem in numpy >=1.15 <1.17
+OCV_OPTION(PYTHON3_LIMITED_API "Build with Python Limited API (not available with numpy >=1.15 <1.17)" NO
+           VISIBLE_IF PYTHON3_NUMPY_VERSION VERSION_LESS "1.15" OR NOT PYTHON3_NUMPY_VERSION VERSION_LESS "1.17")
+if(PYTHON3_LIMITED_API)
+  set(PYTHON3_LIMITED_API_VERSION "0x03060000" CACHE STRING "Minimal Python version for Limited API")
+endif()
 
 if(PYTHON_DEFAULT_EXECUTABLE)
     set(PYTHON_DEFAULT_AVAILABLE "TRUE")

modules/python/common.cmake

@@ -46,6 +46,7 @@ if(${PYTHON}_LIMITED_API)
   # support only python3.3+
   ocv_assert(${PYTHON}_VERSION_MAJOR EQUAL 3 AND ${PYTHON}_VERSION_MINOR GREATER 2)
   target_compile_definitions(${the_module} PRIVATE CVPY_DYNAMIC_INIT)
+  target_compile_definitions(${the_module} PRIVATE PYTHON3_LIMITED_API_VERSION=${PYTHON3_LIMITED_API_VERSION})
   if(WIN32)
     string(REPLACE
       "python${${PYTHON}_VERSION_MAJOR}${${PYTHON}_VERSION_MINOR}.lib"

modules/python/python3/CMakeLists.txt

@@ -2,15 +2,6 @@ if(NOT PYTHON3_INCLUDE_PATH OR NOT PYTHON3_NUMPY_INCLUDE_DIRS)
   ocv_module_disable(python3)
 endif()
 
-# Problem in numpy >=1.15 <1.17
-if(PYTHON3_LIMITED_API
-    AND NOT PYTHON3_NUMPY_VERSION VERSION_LESS "1.15"
-    AND PYTHON3_NUMPY_VERSION VERSION_LESS "1.17"
-  )
-  message(WARNING "Current NUMPY version (${PYTHON3_NUMPY_VERSION}) is not compatible with LIMITED_API.")
-  set(PYTHON3_LIMITED_API OFF)
-endif()
-
 set(the_description "The python3 bindings")
 set(MODULE_NAME python3)
 set(MODULE_INSTALL_SUBDIR python3)

modules/python/src2/cv2.hpp

@@ -13,7 +13,10 @@
 // #define Py_DEBUG
 
 #if defined(CVPY_DYNAMIC_INIT) && !defined(Py_DEBUG)
-#   define Py_LIMITED_API 0x03030000
+#   ifndef PYTHON3_LIMITED_API_VERSION
+#       define PYTHON3_LIMITED_API_VERSION 0x03060000
+#   endif
+#   define Py_LIMITED_API PYTHON3_LIMITED_API_VERSION
 #endif
 
 #include <cmath>