Merge pull request opencv#20221 from komakai:java-at-function

Author: alalek

CMakeLists.txt

@@ -467,6 +467,7 @@ OCV_OPTION(BUILD_ANDROID_SERVICE    "Build OpenCV Manager for Google Play" OFF I
 OCV_OPTION(BUILD_CUDA_STUBS         "Build CUDA modules stubs when no CUDA SDK" OFF  IF (NOT APPLE_FRAMEWORK) )
 OCV_OPTION(BUILD_JAVA               "Enable Java support"                         (ANDROID OR NOT CMAKE_CROSSCOMPILING)  IF (ANDROID OR (NOT APPLE_FRAMEWORK AND NOT WINRT)) )
 OCV_OPTION(BUILD_OBJC               "Enable Objective-C support"                  ON  IF APPLE_FRAMEWORK )
+OCV_OPTION(BUILD_KOTLIN_EXTENSIONS  "Build Kotlin extensions (Android)"           ON  IF ANDROID )
 
 # OpenCV installation options
 # ===================================================

cmake/android/android_gradle_projects.cmake

@@ -2,6 +2,17 @@
 set(ANDROID_GRADLE_PLUGIN_VERSION "3.2.1" CACHE STRING "Android Gradle Plugin version")
 message(STATUS "Android Gradle Plugin version: ${ANDROID_GRADLE_PLUGIN_VERSION}")
 
+set(KOTLIN_PLUGIN_VERSION "1.4.10" CACHE STRING "Kotlin Plugin version")
+message(STATUS "kotlin Plugin version: ${KOTLIN_GRADLE_PLUGIN_VERSION}")
+
+if(BUILD_KOTLIN_EXTENSIONS)
+  set(KOTLIN_PLUGIN_DECLARATION "apply plugin: 'kotlin-android'" CACHE STRING "Kotlin Plugin version")
+  set(KOTLIN_STD_LIB "implementation 'org.jetbrains.kotlin:kotlin-stdlib:${KOTLIN_PLUGIN_VERSION}'" CACHE STRING "Kotlin Standard Library dependency")
+else()
+  set(KOTLIN_PLUGIN_DECLARATION "" CACHE STRING "Kotlin Plugin version")
+  set(KOTLIN_STD_LIB "" CACHE STRING "Kotlin Standard Library dependency")
+endif()
+
 set(GRADLE_VERSION "5.6.4" CACHE STRING "Gradle version")
 message(STATUS "Gradle version: ${GRADLE_VERSION}")