OpenCV and deep learning neural networks

C++
1

Hi to everyone!!! I am pretty new to OpenCV and object detection algorithm., i was able to run some code examples with face detection and recognition using openCV and haarcascades classifiers, but i suppose this methods are “deprecated” and more stable algorithms are based on deep learning and neural networks. When i start to investigate this question i stucked with a huge variations and combinations of deep learning algorithms and i don’t really know from what point to start and what is the best choise for me…

My goal is to make a face mask detection software based on OpenCV and deep learning network model using C++ language (please don’t suggest python).

Could you please help me to find the best combination for my task? I need the whole pipeline: building and training my own deep learning neural network model from scratch (or get pretrained), run openCV detection with that model.

Thank you very much!!! I working on cross platform C++ project in windows PC using Visual Studio 2019.

2

well at least for that part you won’t be able to avoid coding in python
(as you need to use some framework like tf or pytorch for the (re-)training)
((but hey, it’s all C, if you stick with YOLO…))

try to find a simple tutorial on “object-detection” networks

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3

I already found some tutorials with different bunches ncnn+opencv, tensorflow+opencv, but all examples predominantly with python code.

Thank you for a tip about the python coding, i am ready to learn how to create and train model with python, but my main project needs to be in C++.

Could you please do me a favour and advice which bunch to choose for my task:

  1. ncnn+openCV
  2. tensorflow + openCV
  3. caffe + openCV
  4. dnn + openCV
  5. …

And how to choose from a huge plenty of neural networks:

  1. R-CNN
  2. YOLO
  3. HOG
  4. R-FCN
  5. SSD
  6. …

What is the most popular practice? Help to choose please

4
  1. i dont know it, but it looks like inference only (no training there)
  2. we have a “train your own face detection” sample here .
    but no good support for tf>1.5 in opencv
  3. caffe is dead
  4. as 1. no training possible
  5. PyTorch
  6. YOLO (again, if you prefer C …)

cmon mate, just ask the right questions

  • you probably dont need to train from scratch (“fine-tuning”)
  • maybe you can find a pre-trained model, so you can already work on the inference code
2 Likes
5

Thank you for a valuable tips and explanation

6

Finally i decided to start with the following bunch: OpenCV DNN module + Lobe.ai

I successfully trained the model with Lobe (https://www.lobe.ai/) and make two exports for a test one export is a tensorflow “model.pb” format, another is “model.onnx” format, but both of them doesn’t work, i stucked even on model loading part of the code.

Tensorflow load example:

    // load the neural network model
    auto model = cv::dnn::readNet("input/saved_model.pb");
    
    // also try this way
     auto model = cv::dnn::readNetFromTensorflow("input/saved_model.pb");

ONNX load example:

 // load the neural network model
    auto model = cv::dnn::readNetFromONNX("input/model.onnx");

Please help me to win the errors. Thank you

Here is the errors attached when i hit the readNet functions

ONNX errors:

[ERROR:0] global D:\build\opencv_next\modules\dnn\src\onnx\onnx_importer.cpp (2110) cv::dnn::dnn5_v20210608::ONNXImporter::handleNode DNN/ONNX: ERROR during processing node with 1 inputs and 1 outputs: [ReduceMean]:(saved_resnet_50_model/resnet50v2/avg_pool/Mean:0)
OpenCV: terminate handler is called! The last OpenCV error is:
OpenCV(5.0.0-pre) Error: Unspecified error (> Node [ReduceMean]:(saved_resnet_50_model/resnet50v2/avg_pool/Mean:0) parse error: OpenCV(5.0.0-pre) D:\build\opencv_next\modules\dnn\src\onnx\onnx_importer.cpp:725: error: (-215:Assertion failed) axis >= 2 + i in function 'cv::dnn::dnn5_v20210608::ONNXImporter::handleNode'
> ) in cv::dnn::dnn5_v20210608::ONNXImporter::handleNode, file D:\build\opencv_next\modules\dnn\src\onnx\onnx_importer.cpp, line 2129
7

Tensorflow errors:

[libprotobuf ERROR D:\build\opencv_next\3rdparty\protobuf\src\google\protobuf\wire_format_lite.cc:629] String field 'opencv_tensorflow.FunctionDef.Node.ret' contains invalid UTF-8 data when parsing a protocol buffer. Use the 'bytes' type if you intend to send raw bytes.
OpenCV: terminate handler is called! The last OpenCV error is:
OpenCV(5.0.0-pre) Error: Unspecified error (FAILED: ReadProtoFromBinaryFile(param_file, param). Failed to parse GraphDef file: input2/saved_model.pb) in cv::dnn::ReadTFNetParamsFromBinaryFileOrDie, file D:\build\opencv_next\modules\dnn\src\tensorflow\tf_io.cpp, line 42
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can you replace the sceenshots (hated ANYWHERE !) with a TEXT version, so folks here can look up your errors (impossible, given an image ) ? thank you.

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10

Yes, sure! Thank you

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11

unfortunately, its unclear, what you did there, or even what they are using.
impossible to debug
as of now, there is also classification only, right ?

importing tf2 saved_model is not fully supported yet

in the end, rather use something tried and tested

1 Like