Merge pull request #23604 from dkurt:dnn_no_protobuf

Build DNN without Protobuf

DNN module can be built without Protobuf for Darknet, TFLite, OpenVINO, Torch (not PyTorch) models.

```
cmake \
    -DCMAKE_BUILD_TYPE=Release \
    -DBUILD_LIST=dnn \
    -DWITH_PROTOBUF=OFF \
    -DWITH_OPENCL=OFF

7.1M    lib/libopencv_dnn.so.4.7.0
```


```
cmake \
    -DCMAKE_BUILD_TYPE=Release \
    -DBUILD_LIST=dnn \
    -DWITH_OPENCL=OFF

3.9M    lib/libopencv_dnn.so.4.7.0
```

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/dnn/src/caffe/caffe_importer.cpp

@@ -591,7 +591,23 @@ Net readNetFromCaffe(const std::vector<uchar>& bufferProto, const std::vector<uc
                             bufferModelPtr, bufferModel.size());
 }
 
-#endif //HAVE_PROTOBUF
+#else  // HAVE_PROTOBUF
+
+#define DNN_PROTOBUF_UNSUPPORTED() CV_Error(Error::StsError, "DNN/Caffe: Build OpenCV with Protobuf to import Caffe models")
+
+Net readNetFromCaffe(const String &, const String &) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromCaffe(const char *, size_t, const char *, size_t) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromCaffe(const std::vector<uchar>&, const std::vector<uchar>&) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+#endif  // HAVE_PROTOBUF
 
 CV__DNN_INLINE_NS_END
 }} // namespace

modules/dnn/src/init.cpp

@@ -42,7 +42,7 @@
 #include "precomp.hpp"
 #include <opencv2/dnn/layer.details.hpp>
 
-#if !defined(BUILD_PLUGIN)
+#if defined(HAVE_PROTOBUF) && !defined(BUILD_PLUGIN)
 #include <google/protobuf/stubs/common.h>
 #endif
 
@@ -60,7 +60,7 @@ Mutex& getInitializationMutex()
 // force initialization (single-threaded environment)
 Mutex* __initialization_mutex_initializer = &getInitializationMutex();
 
-#if !defined(BUILD_PLUGIN)
+#if defined(HAVE_PROTOBUF) && !defined(BUILD_PLUGIN)
 namespace {
 using namespace google::protobuf;
 class ProtobufShutdown {
@@ -80,7 +80,7 @@ void initializeLayerFactory()
 {
     CV_TRACE_FUNCTION();
 
-#if !defined(BUILD_PLUGIN)
+#if defined(HAVE_PROTOBUF) && !defined(BUILD_PLUGIN)
     static ProtobufShutdown protobufShutdown; CV_UNUSED(protobufShutdown);
 #endif
 

modules/dnn/src/onnx/onnx_graph_simplifier.cpp

@@ -7,6 +7,7 @@
 
 #include "../precomp.hpp"
 
+#ifdef HAVE_PROTOBUF
 #include "../graph_simplifier.hpp"
 #include "onnx_graph_simplifier.hpp"
 
@@ -1265,3 +1266,4 @@ Mat getMatFromTensor(const opencv_onnx::TensorProto& tensor_proto)
 
 CV__DNN_INLINE_NS_END
 }}  // namespace cv::dnn
+#endif  // HAVE_PROTOBUF

modules/dnn/src/onnx/onnx_graph_simplifier.hpp

@@ -7,6 +7,7 @@
 
 #ifndef __OPENCV_DNN_ONNX_SIMPLIFIER_HPP__
 #define __OPENCV_DNN_ONNX_SIMPLIFIER_HPP__
+#ifdef HAVE_PROTOBUF
 
 #if defined(__GNUC__) && __GNUC__ >= 5
 #pragma GCC diagnostic push
@@ -36,4 +37,5 @@ Mat getMatFromTensor(const opencv_onnx::TensorProto& tensor_proto);
 CV__DNN_INLINE_NS_END
 }}  // namespace dnn, namespace cv
 
+#endif  // HAVE_PROTOBUF
 #endif  // __OPENCV_DNN_ONNX_SIMPLIFIER_HPP__

modules/dnn/src/onnx/onnx_importer.cpp

@@ -43,6 +43,7 @@
 #endif
 
 #include "onnx_graph_simplifier.hpp"
+#endif
 
 namespace cv {
 namespace dnn {
@@ -50,6 +51,7 @@ CV__DNN_INLINE_NS_BEGIN
 
 extern bool DNN_DIAGNOSTICS_RUN;
 
+#ifdef HAVE_PROTOBUF
 class ONNXLayerHandler;
 
 template <typename T>
@@ -4170,7 +4172,27 @@ Mat readTensorFromONNX(const String& path)
     return mat;
 }
 
+#else  // HAVE_PROTOBUF
+
+#define DNN_PROTOBUF_UNSUPPORTED() CV_Error(Error::StsError, "DNN/ONNX: Build OpenCV with Protobuf to import ONNX models")
+
+Net readNetFromONNX(const String&) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromONNX(const char*, size_t) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromONNX(const std::vector<uchar>&) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Mat readTensorFromONNX(const String&) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+#endif  // HAVE_PROTOBUF
+
 CV__DNN_INLINE_NS_END
 }} // namespace
-
-#endif

modules/dnn/src/tensorflow/tf_importer.cpp

@@ -36,7 +36,7 @@ CV__DNN_INLINE_NS_BEGIN
 
 extern bool DNN_DIAGNOSTICS_RUN;
 
-#if HAVE_PROTOBUF
+#ifdef HAVE_PROTOBUF
 
 using ::google::protobuf::RepeatedField;
 using ::google::protobuf::RepeatedPtrField;
@@ -3225,8 +3225,6 @@ void TFLayerHandler::handleFailed(const tensorflow::NodeDef& layer)
 
 } // namespace
 
-#endif //HAVE_PROTOBUF
-
 Net readNetFromTensorflow(const String &model, const String &config)
 {
     return detail::readNetDiagnostic<TFImporter>(model.c_str(), config.c_str());
@@ -3276,5 +3274,27 @@ void writeTextGraph(const String& _model, const String& output)
     ofs.close();
 }
 
+#else  // HAVE_PROTOBUF
+
+#define DNN_PROTOBUF_UNSUPPORTED() CV_Error(Error::StsError, "DNN/TF: Build OpenCV with Protobuf to import TensorFlow models")
+
+Net readNetFromTensorflow(const String &, const String &) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromTensorflow(const char*, size_t, const char*, size_t) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+Net readNetFromTensorflow(const std::vector<uchar>&, const std::vector<uchar>&) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+void writeTextGraph(const String& _model, const String& output) {
+    DNN_PROTOBUF_UNSUPPORTED();
+}
+
+#endif  // HAVE_PROTOBUF
+
 CV__DNN_INLINE_NS_END
 }} // namespace