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Image Processing and Duplicate Detection

The workflow uses pre-trained models from OpenCV for face detection and dlib for face recognition and landmark detection. This setup provides a fast, reliable solution for real-time applications, without requiring the training of models from scratch. OpenCV handles face detection using a Caffe-based model, while dlib, accessed through the face_recognition library, manages recognition and duplicate identification.

Future updates will involve custom-trained models to further improve performance.

Inference Mode Operation

This application operates entirely in inference mode, relying on pre-trained models for both face detection and recognition tasks. OpenCV handles face detection, and face_recognition, a Python wrapper for dlib, performs face recognition and duplicate identification. This approach ensures efficient, real-time processing without the need for additional training, allowing the application to quickly deploy its capabilities.

  • OpenCV: Optimized for fast face detection, ideal for real-time image and video applications.
  • dlib's face_recognition: Focuses on generating face embeddings for comparison, providing high accuracy in identification.

By combining OpenCV for detection and dlib for recognition, the system offers a balance of speed and precision.

Pre-Trained Models Storage

  • OpenCV uses a pre-trained Caffe model stored in Azure Blob Storage, automatically downloaded at application startup.
  • face_recognition utilizes a pre-trained dlib model stored locally within the container’s library directory.

Administrators can manually update the Caffe model via the admin panel, allowing flexible updates or new model versions without altering the application code.

Face Detection and Recognition Models

OpenCV Model Details

OpenCV powers the face detection component using a pre-trained model designed for real-time performance.

Model Components

  • deploy.prototxt: Defines the network architecture and parameters for model execution.
  • res10_300x300_ssd_iter_140000.caffemodel: Contains trained weights, generated after 140,000 iterations using the Caffe framework.

Model Architecture

  • Res10 Architecture: A lightweight model that balances speed and accuracy, perfect for real-time detection.
  • 300x300 Input Resolution: Optimized for face detection at this resolution, ensuring a balance between detail and efficiency.
  • SSD (Single Shot MultiBox Detector): A method that predicts bounding boxes and confidence scores in a single pass, allowing rapid detection of multiple faces in a single image.

Dlib Model Details

The dlib models used for recognition and facial landmark detection include:

  1. dlib_face_recognition_resnet_model_v1.dat

    A modified ResNet-34 model generating 128-dimensional face embeddings for face recognition, achieving 99.38% accuracy on the LFW benchmark.

  2. mmod_human_face_detector.dat A CNN-based Max-Margin Object Detector (MMOD) for accurate face detection, especially under difficult conditions like varied orientations or lighting.

  3. shape_predictor_5_face_landmarks.dat Detects 5 key facial landmarks (eye corners and nose base), optimized for fast face alignment.

  4. shape_predictor_68_face_landmarks.dat Detects 68 facial landmarks (eyes, nose, mouth, jawline), used for more detailed facial alignment and analysis.

Workflow Diagram

The workflow diagram illustrates the overall process of image processing and duplicate detection. OpenCV is used for face detection, while face_recognition (built on dlib) handles face recognition and duplicate identification.

flowchart LR
  subgraph ImageProcessing[Image Processing]
      direction LR

      subgraph FaceDetection[Face Detection]

        subgraph DNNManager[DNN Manager]
            direction TB
            load_model[Load Caffe Model] -- computation <a href="../config/#dnn_backend">backend</a>\ntarget <a href="../config/#dnn_target">device</a>  --> set_preferences[Set Preferences]
        end

          DNNManager --> run_model

          direction TB
          load_image[Load Image] -- decoded image as 3D numpy array\n(height, width, channels of BlueGreeRed color space) --> prepare_image[Prepare Image] -- blob 4D tensor\n(normalized size, use <a href="../config/#blob_from_image_scale_factor">scale factor</a> and <a href="../config/#blob_from_image_mean_values">means</a>) --> run_model[Run Model] -- shape (1, 1, N, 7),\n1 image\nN is the number of detected faces\neach face is described by the 7 detection values--> filter_results[Filter Results] -- <a href="../config/#face_detection_confidence">confidence</a> is above the minimum threshold,\n<a href="../config/#nms_threshold">NMS</a> to suppress overlapping bounding boxes --> return_detections[Return Detections]
      end

      subgraph FaceRecognition[Face Recognition]
          direction TB
          load_image_[Load Image] --> detect_faces[Detect Faces] -- detected face regions\n<a href="../config/#face_encodings_num_jitters">number of times</a> to re-sample the face\n<a href="../config/#face_encodings_model">key facial landmarks</a> --> generate_encodings[Generate Encodings] -- numerical representations of the facial features\n(face's geometry and appearance) --> save_encodings[Save Encodings]
      end
  end

  subgraph DuplicateFinder[Duplicate Finder]
      direction TB
      load_encodings[Load Encodings] --> compare_encodings[Compare Encodings] -- face distance less then <a href="../config/#face_distance_threshold">threshold</a> --> return_duplicates[Return Duplicates]
  end

  ImageProcessing --> DuplicateFinder
  FaceDetection --> FaceRecognition