Merge pull request opencv#19474 from aryanshomray:darknet_tanh

Author: alalek

modules/dnn/src/darknet/darknet_io.cpp

@@ -241,6 +241,10 @@ namespace cv {
                     {
                         activation_param.type = "Sigmoid";
                     }
+                    else if (type == "tanh")
+                    {
+                        activation_param.type = "TanH";
+                    }
                     else
                     {
                         CV_Error(cv::Error::StsParseError, "Unsupported activation: " + type);

modules/dnn/test/test_darknet_importer.cpp

@@ -702,6 +702,11 @@ TEST_P(Test_Darknet_layers, mish)
     testDarknetLayer("mish", true);
 }
 
+TEST_P(Test_Darknet_layers, tanh)
+{
+    testDarknetLayer("tanh");
+}
+
 TEST_P(Test_Darknet_layers, avgpool_softmax)
 {
     testDarknetLayer("avgpool_softmax");