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Image Comparison: Dataset Format, Training, and Inference

We use a Siamese network for comparing images (e.g. objects or faces). As in the case of object detection, we use a PyTorch-based model for this purpose.

Dataset Format

The Siamese network training script expects a data directory with multiple subdirectories - one per object - where each such directory contains images corresponding to the same object. The expected directory structure is shown below:

    train_dataset_dir
    |    obj_1
    |    |    1.jpg
    |    |    ...
    |    |____n.jpg
    |    obj_2
    |    |    1.jpg
    |    |    ...
    |    |____n.jpg
    |    ...
    |____obj_n
         |    1.jpg
         |    ...
         |____n.jpg

Training a Comparison Model

For training a comparison model, the train_siamese_net.py script, which can be found under scripts, should be used. The script accepts the following arguments:

  • -d --data_path: Directory containing training (default /home/lucy/data)
  • -m --model_path: Path to a directory where the trained models (one per epoch) should be saved (default /home/lucy/models)
  • -e --num_epochs: Number of training epochs (default 10)
  • -lr --learning_rate: Initial learning rate (default 1e-4)
  • -b --training_batch_size: Training batch size (default 1)
  • -l --train_loss_file_path: Path to a file in which training losses will be saved (default /home/lucy/data/train_loss.log)

An example call is given below:

./train_siamese_net.py \
-d /home/lucy/images/ \
-m /home/lucy/models \
-e 10 \
-lr 0.0001 \
-b 64 \
-l /home/lucy/training_loss.log

Using a Comparison Model

The script test_siamese_net.py, also included under scripts, illustrates the use of a trained model for calculating the difference between two images. This script takes the following arguments:

  • -i1 --image1_path: Path to an image (default '')
  • -i2 --image2_path: Path to an image to be compared (default '')
  • -m --model_path: Path to a trained model (default /home/lucy/data/model.pt)

An example call is given below:

./test_siamese_net.py \
-i1 /home/lucy/img1.jpg \
-i2 /home/lucy/img2.jpg \
-m /home/lucy/models/model.pt