Merge pull request opencv#19597 from komakai:android-ndk-camera

Android NDK camera support

* Add native camera video backend for Android

* In the event of a "No buffer available error" wait for the appropriate callback and retry

* Fix stale context when creating a new AndroidCameraCapture

* Add property handling

CMakeLists.txt

@@ -437,6 +437,9 @@ OCV_OPTION(WITH_QUIRC "Include library QR-code decoding" ON
 OCV_OPTION(WITH_ANDROID_MEDIANDK "Use Android Media NDK for Video I/O (Android)" (ANDROID_NATIVE_API_LEVEL GREATER 20)
   VISIBLE_IF ANDROID
   VERIFY HAVE_ANDROID_MEDIANDK)
+OCV_OPTION(WITH_ANDROID_NATIVE_CAMERA "Use Android NDK for Camera I/O (Android)" (ANDROID_NATIVE_API_LEVEL GREATER 23)
+  VISIBLE_IF ANDROID
+  VERIFY HAVE_ANDROID_NATIVE_CAMERA)
 OCV_OPTION(WITH_TENGINE "Include Arm Inference Tengine support" OFF
   VISIBLE_IF (ARM OR AARCH64) AND (UNIX OR ANDROID) AND NOT IOS
   VERIFY HAVE_TENGINE)

cmake/android/android_gradle_projects.cmake

@@ -6,7 +6,11 @@ set(GRADLE_VERSION "5.6.4" CACHE STRING "Gradle version")
 message(STATUS "Gradle version: ${GRADLE_VERSION}")
 
 set(ANDROID_COMPILE_SDK_VERSION "26" CACHE STRING "Android compileSdkVersion")
-set(ANDROID_MIN_SDK_VERSION "21" CACHE STRING "Android minSdkVersion")
+if(ANDROID_NATIVE_API_LEVEL GREATER 21)
+  set(ANDROID_MIN_SDK_VERSION "${ANDROID_NATIVE_API_LEVEL}" CACHE STRING "Android minSdkVersion")
+else()
+  set(ANDROID_MIN_SDK_VERSION "21" CACHE STRING "Android minSdkVersion")
+endif()
 set(ANDROID_TARGET_SDK_VERSION "26" CACHE STRING "Android minSdkVersion")
 
 set(ANDROID_BUILD_BASE_DIR "${OpenCV_BINARY_DIR}/opencv_android" CACHE INTERNAL "")

modules/java/android_sdk/CMakeLists.txt

@@ -96,7 +96,11 @@ FILE(MAKE_DIRECTORY \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${JAVA_INSTALL_ROOT
 
 ocv_update(ANDROID_COMPILE_SDK_VERSION "27")
 ocv_update(ANDROID_MIN_SDK_VERSION "14")
-ocv_update(ANDROID_TARGET_SDK_VERSION "21")
+if(ANDROID_NATIVE_API_LEVEL GREATER 21)
+  ocv_update(ANDROID_TARGET_SDK_VERSION "${ANDROID_NATIVE_API_LEVEL}")
+else()
+  ocv_update(ANDROID_TARGET_SDK_VERSION "21")
+endif()
 configure_file("${CMAKE_CURRENT_SOURCE_DIR}/build.gradle.in" "${CMAKE_CURRENT_BINARY_DIR}/build.gradle" @ONLY)
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/build.gradle" DESTINATION ${JAVA_INSTALL_ROOT}/.. COMPONENT java)
 

modules/videoio/CMakeLists.txt

@@ -201,6 +201,12 @@ if(TARGET ocv.3rdparty.android_mediandk)
   list(APPEND tgts ocv.3rdparty.android_mediandk)
 endif()
 
+if(TARGET ocv.3rdparty.android_native_camera)
+  list(APPEND videoio_srcs
+    ${CMAKE_CURRENT_LIST_DIR}/src/cap_android_camera.cpp)
+  list(APPEND tgts ocv.3rdparty.android_native_camera)
+endif()
+
 ocv_set_module_sources(HEADERS ${videoio_ext_hdrs} ${videoio_hdrs} SOURCES ${videoio_srcs})
 ocv_module_include_directories()
 ocv_create_module()

modules/videoio/cmake/detect_android_camera.cmake

@@ -0,0 +1,8 @@
+# if(ANDROID AND ANDROID_NATIVE_API_LEVEL GREATER_EQUAL 24)  <-- would be nicer but requires CMake 3.7 or later
+if(ANDROID AND ANDROID_NATIVE_API_LEVEL GREATER 23)
+  set(HAVE_ANDROID_NATIVE_CAMERA TRUE)
+  set(libs "-landroid -llog -lcamera2ndk")
+  ocv_add_external_target(android_native_camera "" "${libs}" "HAVE_ANDROID_NATIVE_CAMERA")
+endif()
+
+set(HAVE_ANDROID_NATIVE_CAMERA ${HAVE_ANDROID_NATIVE_CAMERA} PARENT_SCOPE)

modules/videoio/cmake/init.cmake

@@ -37,3 +37,4 @@ add_backend("dshow" WITH_DSHOW)
 add_backend("msmf" WITH_MSMF)
 
 add_backend("android_mediandk" WITH_ANDROID_MEDIANDK)
+add_backend("android_camera" WITH_ANDROID_NATIVE_CAMERA)