Fix a dnn bug with retrieving all the output blobs

modules/dnn/src/dnn.cpp

@@ -2795,8 +2795,7 @@ void Net::forward(std::vector<std::vector<Mat> >& outputBlobs,
     std::vector<LayerPin> pins;
     for (int i = 0; i < outBlobNames.size(); i++)
     {
-        std::vector<LayerPin> lp = impl->getLayerOutPins(outBlobNames[i]);
-        pins.insert(pins.end(), lp.begin(), lp.end());
+        pins.push_back(impl->getPinByAlias(outBlobNames[i]));
     }
 
     impl->setUpNet(pins);
@@ -2809,9 +2808,10 @@ void Net::forward(std::vector<std::vector<Mat> >& outputBlobs,
     for (int i = 0; i < outBlobNames.size(); i++)
     {
         std::vector<LayerPin> lp = impl->getLayerOutPins(outBlobNames[i]);
-        for (int i = 0; i < lp.size(); i++)
+        outputBlobs[i].resize(lp.size());
+        for (int j = 0; j < lp.size(); j++)
         {
-            outputBlobs[i].push_back(impl->getBlob(lp[i]));
+            outputBlobs[i][j] = impl->getBlob(lp[j]);
         }
     }
 }

modules/dnn/test/test_misc.cpp

@@ -306,4 +306,38 @@ TEST_P(DeprecatedForward, CustomLayerWithFallback)
 
 INSTANTIATE_TEST_CASE_P(/**/, DeprecatedForward, dnnBackendsAndTargets());
 
+TEST(Net, forwardAndRetrieve)
+{
+    std::string prototxt =
+        "input: \"data\"\n"
+        "layer {\n"
+        "  name: \"testLayer\"\n"
+        "  type: \"Slice\"\n"
+        "  bottom: \"data\"\n"
+        "  top: \"firstCopy\"\n"
+        "  top: \"secondCopy\"\n"
+        "  slice_param {\n"
+        "    axis: 0\n"
+        "    slice_point: 2\n"
+        "  }\n"
+        "}";
+    Net net = readNetFromCaffe(&prototxt[0], prototxt.size());
+    net.setPreferableBackend(DNN_BACKEND_OPENCV);
+
+    Mat inp(4, 5, CV_32F);
+    randu(inp, -1, 1);
+    net.setInput(inp);
+
+    std::vector<String> outNames;
+    outNames.push_back("testLayer");
+    std::vector<std::vector<Mat> > outBlobs;
+
+    net.forward(outBlobs, outNames);
+
+    EXPECT_EQ(outBlobs.size(), 1);
+    EXPECT_EQ(outBlobs[0].size(), 2);
+    normAssert(outBlobs[0][0], inp.rowRange(0, 2), "first part");
+    normAssert(outBlobs[0][1], inp.rowRange(2, 4), "second part");
+}
+
 }} // namespace