Merge pull request #18451 from OrestChura:oc/count_non_zero

[G-API]: countNonZero() Standard Kernel Implementation

* Add countNonZero() standard kernel
 - API and documentation provided
 - OCV backend supported
 - accuracy and performance tests provided
 - some refactoring of related documentation done

* Fix GOpaque functionality for OCL Backend
 - test for OCL Opaque usage providied

* countNonZero for GPU
 - OCL Backend implementation for countNonZero() added
 - tests provided

* Addressing comments

modules/gapi/src/backends/cpu/gcpucore.cpp

@@ -2,7 +2,7 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html.
 //
-// Copyright (C) 2018 Intel Corporation
+// Copyright (C) 2018-2020 Intel Corporation
 
 
 #include "precomp.hpp"
@@ -342,6 +342,14 @@ GAPI_OCV_KERNEL(GCPUSum, cv::gapi::core::GSum)
     }
 };
 
+GAPI_OCV_KERNEL(GCPUCountNonZero, cv::gapi::core::GCountNonZero)
+{
+    static void run(const cv::Mat& in, int& out)
+    {
+        out = cv::countNonZero(in);
+    }
+};
+
 GAPI_OCV_KERNEL(GCPUAddW, cv::gapi::core::GAddW)
 {
     static void run(const cv::Mat& in1, double alpha, const cv::Mat& in2, double beta, double gamma, int dtype, cv::Mat& out)
@@ -679,6 +687,7 @@ cv::gapi::GKernelPackage cv::gapi::core::cpu::kernels()
          , GCPUAbsDiff
          , GCPUAbsDiffC
          , GCPUSum
+         , GCPUCountNonZero
          , GCPUAddW
          , GCPUNormL1
          , GCPUNormL2

modules/gapi/src/backends/ocl/goclcore.cpp

@@ -2,7 +2,7 @@
 // It is subject to the license terms in the LICENSE file found in the top-level directory
 // of this distribution and at http://opencv.org/license.html.
 //
-// Copyright (C) 2018 Intel Corporation
+// Copyright (C) 2018-2020 Intel Corporation
 
 
 #include "precomp.hpp"
@@ -337,6 +337,14 @@ GAPI_OCL_KERNEL(GOCLSum, cv::gapi::core::GSum)
     }
 };
 
+GAPI_OCL_KERNEL(GOCLCountNonZero, cv::gapi::core::GCountNonZero)
+{
+    static void run(const cv::UMat& in, int& out)
+    {
+        out = cv::countNonZero(in);
+    }
+};
+
 GAPI_OCL_KERNEL(GOCLAddW, cv::gapi::core::GAddW)
 {
     static void run(const cv::UMat& in1, double alpha, const cv::UMat& in2, double beta, double gamma, int dtype, cv::UMat& out)
@@ -565,6 +573,7 @@ cv::gapi::GKernelPackage cv::gapi::core::ocl::kernels()
          , GOCLAbsDiff
          , GOCLAbsDiffC
          , GOCLSum
+         , GOCLCountNonZero
          , GOCLAddW
          , GOCLNormL1
          , GOCLNormL2

modules/gapi/src/backends/ocl/goclkernel.cpp

@@ -34,6 +34,11 @@ cv::detail::VectorRef& cv::GOCLContext::outVecRef(int output)
     return util::get<cv::detail::VectorRef>(m_results.at(output));
 }
 
+cv::detail::OpaqueRef& cv::GOCLContext::outOpaqueRef(int output)
+{
+    return util::get<cv::detail::OpaqueRef>(m_results.at(output));
+}
+
 cv::GOCLKernel::GOCLKernel()
 {
 }