Make external cv::dnn::Importer usage is deprecated

modules/dnn/src/caffe/caffe_importer.cpp

@@ -370,24 +370,15 @@ Ptr<Importer> createCaffeImporter(const String &prototxt, const String &caffeMod
     return Ptr<Importer>(new CaffeImporter(prototxt.c_str(), caffeModel.c_str()));
 }
 
-#else //HAVE_PROTOBUF
-
-Ptr<Importer> createCaffeImporter(const String&, const String&)
+Net readNetFromCaffe(const String &prototxt, const String &caffeModel /*= String()*/)
 {
-    CV_Error(cv::Error::StsNotImplemented, "libprotobuf required to import data from Caffe models");
-    return Ptr<Importer>();
+    CaffeImporter caffeImporter(prototxt.c_str(), caffeModel.c_str());
+    Net net;
+    caffeImporter.populateNet(net);
+    return net;
 }
 
 #endif //HAVE_PROTOBUF
 
-Net readNetFromCaffe(const String &prototxt, const String &caffeModel /*= String()*/)
-{
-    Ptr<Importer> caffeImporter = createCaffeImporter(prototxt, caffeModel);
-    Net net;
-    if (caffeImporter)
-        caffeImporter->populateNet(net);
-    return net;
-}
-
 CV__DNN_EXPERIMENTAL_NS_END
 }} // namespace

modules/dnn/src/tensorflow/tf_importer.cpp

@@ -1045,10 +1045,9 @@ Ptr<Importer> createTensorflowImporter(const String&)
 
 Net readNetFromTensorflow(const String &model)
 {
-    Ptr<Importer> importer = createTensorflowImporter(model);
+    TFImporter importer(model.c_str());
     Net net;
-    if (importer)
-        importer->populateNet(net);
+    importer.populateNet(net);
     return net;
 }
 

modules/dnn/src/torch/torch_importer.cpp

@@ -1150,10 +1150,9 @@ Net readNetFromTorch(const String &model, bool isBinary)
 {
     CV_TRACE_FUNCTION();
 
-    Ptr<Importer> importer = createTorchImporter(model, isBinary);
+    TorchImporter importer(model, isBinary);
     Net net;
-    if (importer)
-        importer->populateNet(net);
+    importer.populateNet(net);
     return net;
 }