Merge pull request #15057 from l-bat:fix_vizualizer

* Fix dumpToFile

* Add test

* Fix test

modules/dnn/include/opencv2/dnn/dnn.hpp

@@ -387,7 +387,7 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
 
         /** @brief Dump net to String
          *  @returns String with structure, hyperparameters, backend, target and fusion
-         *  To see correct backend, target and fusion run after forward().
+         *  Call method after setInput(). To see correct backend, target and fusion run after forward().
          */
         CV_WRAP String dump();
         /** @brief Dump net structure, hyperparameters, backend, target and fusion to dot file

modules/dnn/src/dnn.cpp

@@ -2903,6 +2903,13 @@ String parseLayerParams(const String& name, const LayerParams& lp) {
 String Net::dump()
 {
     CV_Assert(!empty());
+
+    if (impl->netInputLayer->inputsData.empty())
+        CV_Error(Error::StsError, "Requested set input");
+
+    if (!impl->netWasAllocated)
+        impl->setUpNet();
+
     std::ostringstream out;
     std::map<int, LayerData>& map = impl->layers;
     int prefBackend = impl->preferableBackend;

modules/dnn/test/test_misc.cpp

@@ -78,6 +78,26 @@ TEST(readNet, Regression)
     EXPECT_FALSE(net.empty());
 }
 
+typedef testing::TestWithParam<tuple<Backend, Target> > dump;
+TEST_P(dump, Regression)
+{
+    const int backend  = get<0>(GetParam());
+    const int target   = get<1>(GetParam());
+    Net net = readNet(findDataFile("dnn/squeezenet_v1.1.prototxt"),
+                      findDataFile("dnn/squeezenet_v1.1.caffemodel", false));
+
+    int size[] = {1, 3, 227, 227};
+    Mat input = cv::Mat::ones(4, size, CV_32F);
+    net.setInput(input);
+    net.setPreferableBackend(backend);
+    net.setPreferableTarget(target);
+    EXPECT_FALSE(net.dump().empty());
+    net.forward();
+    EXPECT_FALSE(net.dump().empty());
+}
+
+INSTANTIATE_TEST_CASE_P(/**/, dump, dnnBackendsAndTargets());
+
 class FirstCustomLayer CV_FINAL : public Layer
 {
 public: