Merge pull request #28678 from omrope79:caffe-importer-cleanup

Caffe importer cleanup #28678

Merge with: https://github.com/opencv/opencv_extra/pull/1324

### 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
- [x] The feature is well documented and sample code can be built with the project CMake

modules/objdetect/src/barcode.cpp

@@ -348,11 +348,13 @@ BarcodeDetector::BarcodeDetector(const string &prototxt_path, const string &mode
     Ptr<BarcodeImpl> p_ = new BarcodeImpl();
     p = p_;
     p_->sr = make_shared<SuperScale>();
-    if (!prototxt_path.empty() && !model_path.empty())
+    // The Super Resolution model is now a single-file ONNX network; the legacy Caffe
+    // prototxt argument is retained for API compatibility but is no longer used.
+    CV_UNUSED(prototxt_path);
+    if (!model_path.empty())
     {
-        CV_Assert(utils::fs::exists(prototxt_path));
         CV_Assert(utils::fs::exists(model_path));
-        int res = p_->sr->init(prototxt_path, model_path);
+        int res = p_->sr->init(model_path);
         CV_Assert(res == 0);
         p_->use_nn_sr = true;
     }

modules/objdetect/src/barcode_decoder/common/super_scale.cpp

@@ -18,9 +18,10 @@ namespace barcode {
 
 constexpr static float MAX_SCALE = 4.0f;
 
-int SuperScale::init(const std::string &proto_path, const std::string &model_path)
+int SuperScale::init(const std::string &model_path)
 {
-    srnet_ = dnn::readNetFromCaffe(proto_path, model_path);
+    // Super Resolution is loaded from a single-file ONNX model (e.g. dnn/wechat_2021-01/sr.onnx).
+    srnet_ = dnn::readNetFromONNX(model_path);
     net_loaded_ = true;
     return 0;
 }
@@ -77,9 +78,8 @@ int SuperScale::superResolutionScale(const Mat &src, Mat &dst)
 
 #else // HAVE_OPENCV_DNN
 
-int SuperScale::init(const std::string &proto_path, const std::string &model_path)
+int SuperScale::init(const std::string &model_path)
 {
-    CV_UNUSED(proto_path);
     CV_UNUSED(model_path);
     return 0;
 }

modules/objdetect/src/barcode_decoder/common/super_scale.hpp

@@ -22,7 +22,7 @@ public:
 
     ~SuperScale() = default;
 
-    int init(const std::string &proto_path, const std::string &model_path);
+    int init(const std::string &model_path);
 
     void processImageScale(const Mat &src, Mat &dst, float scale, const bool &use_sr, int sr_max_size = 160);