Added CMake configuration OPENCV_DNN_BACKEND_DEFAULT

CMakeLists.txt

@@ -1672,6 +1672,10 @@ else()
   endif()
 endif()
 
+if(BUILD_opencv_dnn)
+    status("    Default DNN backend:" ${OPENCV_DNN_BACKEND_DEFAULT})
+endif()
+
 if(WITH_EIGEN OR HAVE_EIGEN)
   status("    Eigen:"      HAVE_EIGEN       THEN "YES (ver ${EIGEN_WORLD_VERSION}.${EIGEN_MAJOR_VERSION}.${EIGEN_MINOR_VERSION})" ELSE NO)
 endif()

modules/dnn/CMakeLists.txt

@@ -227,6 +227,9 @@ if(TARGET ocv.3rdparty.openvino AND OPENCV_DNN_OPENVINO)
   endif()
 endif()
 
+set(OPENCV_DNN_BACKEND_DEFAULT "DNN_BACKEND_OPENCV" CACHE STRING "Default backend used by the DNN module")
+ocv_append_source_file_compile_definitions("${CMAKE_CURRENT_LIST_DIR}/src/dnn_params.cpp" "OPENCV_DNN_BACKEND_DEFAULT=${OPENCV_DNN_BACKEND_DEFAULT}")
+
 
 ocv_install_used_external_targets(${libs} ${dnn_runtime_libs})
 

modules/dnn/include/opencv2/dnn/dnn.hpp

@@ -69,9 +69,7 @@ CV__DNN_INLINE_NS_BEGIN
      */
     enum Backend
     {
-        //! DNN_BACKEND_DEFAULT equals to DNN_BACKEND_INFERENCE_ENGINE if
+        //! DNN_BACKEND_DEFAULT equals to OPENCV_DNN_BACKEND_DEFAULT, which can be defined using CMake or a configuration parameter
-        //! OpenCV is built with Intel OpenVINO or
-        //! DNN_BACKEND_OPENCV otherwise.
         DNN_BACKEND_DEFAULT = 0,
         DNN_BACKEND_HALIDE,
         DNN_BACKEND_INFERENCE_ENGINE,            //!< Intel OpenVINO computational backend
@@ -688,9 +686,6 @@ CV__DNN_INLINE_NS_BEGIN
          * @brief Ask network to use specific computation backend where it supported.
          * @param[in] backendId backend identifier.
          * @see Backend
-         *
-         * If OpenCV is compiled with Intel's Inference Engine library, DNN_BACKEND_DEFAULT
-         * means DNN_BACKEND_INFERENCE_ENGINE. Otherwise it equals to DNN_BACKEND_OPENCV.
          */
         CV_WRAP void setPreferableBackend(int backendId);
 

modules/dnn/src/dnn_params.cpp

@@ -36,7 +36,7 @@ bool getParam_DNN_OPENCL_ALLOW_ALL_DEVICES()
 int getParam_DNN_BACKEND_DEFAULT()
 {
     static int PARAM_DNN_BACKEND_DEFAULT = (int)utils::getConfigurationParameterSizeT("OPENCV_DNN_BACKEND_DEFAULT",
-            (size_t)DNN_BACKEND_OPENCV
+            (size_t)OPENCV_DNN_BACKEND_DEFAULT
     );
     return PARAM_DNN_BACKEND_DEFAULT;
 }