Merge pull request #14150 from TolyaTalamanov:at/computation-doesnt-work-with-out-vector

G-API: GComputation doesn't work with output vector<cv::Mat> (#14150)

* Fix bug with gcomputation output vector

* Add test fixture

* Fix comments to review

* Fix alignment

modules/gapi/include/opencv2/gapi/gcomputation.hpp

@@ -315,7 +315,7 @@ public:
      * inputs/outputs which were used to define this GComputation.
      */
     void apply(const std::vector<cv::Mat>& ins,         // Compatibility overload
-               const std::vector<cv::Mat>& outs,
+                     std::vector<cv::Mat>& outs,
                GCompileArgs &&args = {});
 #endif // !defined(GAPI_STANDALONE)
     // Various versions of compile(): //////////////////////////////////////////

modules/gapi/src/api/gcomputation.cpp

@@ -159,16 +159,14 @@ void cv::GComputation::apply(cv::Mat in1, cv::Mat in2, cv::Scalar &out, GCompile
 }
 
 void cv::GComputation::apply(const std::vector<cv::Mat> &ins,
-                             const std::vector<cv::Mat> &outs,
+                                   std::vector<cv::Mat> &outs,
                              GCompileArgs &&args)
 {
     GRunArgs call_ins;
     GRunArgsP call_outs;
 
-    // Make a temporary copy of vector outs - cv::Mats are copies anyway
-    auto tmp = outs;
-    for (const cv::Mat &m : ins) { call_ins.emplace_back(m);   }
-    for (      cv::Mat &m : tmp) { call_outs.emplace_back(&m); }
+    for (const cv::Mat &m : ins)  { call_ins.emplace_back(m);   }
+    for (      cv::Mat &m : outs) { call_outs.emplace_back(&m); }
 
     apply(std::move(call_ins), std::move(call_outs), std::move(args));
 }

modules/gapi/test/gapi_gcomputation_tests.cpp

@@ -7,6 +7,7 @@
 
 #include "test_precomp.hpp"
 #include "opencv2/gapi/cpu/gcpukernel.hpp"
+#include <ade/util/zip_range.hpp>
 
 namespace opencv_test
 {
@@ -51,6 +52,41 @@ namespace opencv_test
           {
           }
       };
+
+      struct GComputationVectorMatsAsOutput: public ::testing::Test
+      {
+          cv::Mat  in_mat;
+          cv::GComputation m_c;
+          std::vector<cv::Mat> ref_mats;
+
+          GComputationVectorMatsAsOutput() : in_mat(300, 300, CV_8UC3),
+          m_c([&](){
+                      cv::GMat in;
+                      cv::GMat out[3];
+                      std::tie(out[0], out[1], out[2]) = cv::gapi::split3(in);
+                      return cv::GComputation({in}, {out[0], out[1], out[2]});
+                  })
+          {
+              cv::randu(in_mat, cv::Scalar::all(0), cv::Scalar::all(255));
+              cv::split(in_mat, ref_mats);
+          }
+
+          void run(std::vector<cv::Mat>& out_mats)
+          {
+              m_c.apply({in_mat}, out_mats);
+          }
+
+          void check(const std::vector<cv::Mat>& out_mats)
+          {
+              for (const auto& it : ade::util::zip(ref_mats, out_mats))
+              {
+                  const auto& ref_mat = std::get<0>(it);
+                  const auto& out_mat = std::get<1>(it);
+
+                  EXPECT_EQ(0, cv::countNonZero(ref_mat != out_mat));
+              }
+          }
+      };
   }
 
   TEST_F(GComputationApplyTest, ThrowDontPassCustomKernel)
@@ -65,4 +101,37 @@ namespace opencv_test
       ASSERT_NO_THROW(m_c.apply(in_mat, out_mat, cv::compile_args(pkg)));
   }
 
+  TEST_F(GComputationVectorMatsAsOutput, OutputAllocated)
+  {
+      std::vector<cv::Mat> out_mats(3);
+      for (auto& out_mat : out_mats)
+      {
+          out_mat.create(in_mat.size(), CV_8UC1);
+      }
+
+      run(out_mats);
+      check(out_mats);
+  }
+
+  TEST_F(GComputationVectorMatsAsOutput, OutputNotAllocated)
+  {
+      std::vector<cv::Mat> out_mats(3);
+
+      run(out_mats);
+      check(out_mats);
+  }
+
+  TEST_F(GComputationVectorMatsAsOutput, OutputAllocatedWithInvalidMeta)
+  {
+      std::vector<cv::Mat> out_mats(3);
+
+      for (auto& out_mat : out_mats)
+      {
+          out_mat.create(in_mat.size() / 2, CV_8UC1);
+      }
+
+      run(out_mats);
+      check(out_mats);
+  }
+
 } // namespace opencv_test