Merge pull request #28646 from abhishek-gola:kernel_values

Fix kernel shape handling in ONNX importer2 #28646

Requires opencv_extra: https://github.com/opencv/opencv_extra/pull/1323
closes: https://github.com/opencv/opencv/issues/28321

### 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/onnx/onnx_graph_simplifier.cpp

@@ -1728,6 +1728,15 @@ void simplifySubgraphs(opencv_onnx::GraphProto& net)
 }
 
 
+static std::string getExternalDataValue(const opencv_onnx::TensorProto& tensor_proto, const std::string& key)
+{
+    for (const auto& entry : tensor_proto.external_data())
+    {
+        if (entry.key() == key)
+            return entry.value();
+    }
+    return std::string();
+}
 
 static char* getTensorRAWData(const opencv_onnx::TensorProto& tensor_proto,
                               std::vector<int64_t>& tensor_data, const std::string& base_path = "")
@@ -1735,24 +1744,31 @@ static char* getTensorRAWData(const opencv_onnx::TensorProto& tensor_proto,
     if (tensor_proto.has_data_location() && tensor_proto.data_location() == opencv_onnx::TensorProto::EXTERNAL) {
     #if OPENCV_HAVE_FILESYSTEM_SUPPORT
         CV_Assert(tensor_proto.has_data_location() && tensor_proto.data_location() == opencv_onnx::TensorProto::EXTERNAL);
-        auto it_begin = tensor_proto.external_data().begin();
-        auto it_end = tensor_proto.external_data().end();
-        // file path
-        auto it = std::find_if(it_begin, it_end,[](const auto& entry) { return entry.key() == "location"; });
-        CV_CheckTrue(it != it_end, "External tensor data location is not specified");
+        std::string location_path = getExternalDataValue(tensor_proto, "location");
+        CV_CheckTrue(!location_path.empty(), "External tensor data location is not specified");
 
-
-        std::string location_path = it->value();
         std::string full_path = base_path.empty() ? location_path : utils::fs::join(base_path, location_path);
 
         std::ifstream file(full_path, std::ios::binary | std::ios::ate);
         CV_CheckTrue(file.is_open(), "Failed to open external tensor data file");
 
-        size_t size = file.tellg();
-        file.seekg(0, std::ios::beg);
-        tensor_data.resize(divUp((size_t)size, sizeof(int64_t)));
+        size_t file_size = (size_t)file.tellg();
+        size_t offset = 0;
+        std::string offset_str = getExternalDataValue(tensor_proto, "offset");
+        if (!offset_str.empty())
+            offset = (size_t)std::stoull(offset_str);
 
-        file.read((char*)tensor_data.data(), size);
+        size_t length = file_size - offset;
+        std::string length_str = getExternalDataValue(tensor_proto, "length");
+        if (!length_str.empty())
+            length = (size_t)std::stoull(length_str);
+
+        CV_Check(offset, offset <= file_size, "External data offset exceeds file size");
+        CV_Check(length, length <= file_size - offset, "External data length exceeds available bytes");
+
+        file.seekg(offset, std::ios::beg);
+        tensor_data.resize(divUp(length, sizeof(int64_t)));
+        file.read((char*)tensor_data.data(), length);
         return (char*)tensor_data.data();
     #else
         CV_Error(Error::StsNotImplemented, "External tensor data is not supported without filesystem support");

modules/dnn/src/onnx/onnx_importer2.cpp

@@ -1370,7 +1370,7 @@ void ONNXImporter2::parseConv(LayerParams& layerParams, const opencv_onnx::NodeP
     int n_inputs = node_proto.input_size();
     CV_Assert(2 <= n_inputs && n_inputs <= 3);
     layerParams.type = "Conv2";
-    addLayer(layerParams, node_proto);
+    addLayer(layerParams, node_proto, n_inputs);
 }
 
 void ONNXImporter2::parseConvTranspose(LayerParams& layerParams, const opencv_onnx::NodeProto& node_proto)

modules/dnn/test/test_onnx_importer.cpp

@@ -2563,6 +2563,12 @@ TEST_P(Test_ONNX_nets, MobileNet_v2_FP16)
     testONNXModels("mobilenetv2_fp16", npy, default_l1, default_lInf, true);
 }
 
+TEST_P(Test_ONNX_nets, MobileNet_v4)
+{
+    required = true;
+    testONNXModels("mobilenetv4", npy, default_l1, default_lInf, true);
+}
+
 TEST_P(Test_ONNX_nets, LResNet100E_IR)
 {
     applyTestTag(