frechet-coefficient 1.0.4

Frechet Coefficient

Frechet Coefficient

Frechet Coefficient is a Python package for calculating various similarity metrics between images, including Frechet Distance, Frechet Coefficient, and Hellinger Distance. It leverages pre-trained models from TensorFlow's Keras applications to extract features from images.

Table of Contents

• Installation
• Usage
• Features
• Citation
• License

Installation

To install the package, use the following command:

pip install frechet-coefficient

Requirements:

• Python 3.10-3.12
• TensorFlow 2.18.*
• imageio 2.36.*

Usage

You can use the command-line interface (CLI) to calculate similarity metrics between two directories of images.

frechet-coefficient <path_to_directory1> <path_to_directory2> --metric <metric> [options]

Remember to use enough images to get a meaningful result. If your datasets are small, consider using --random_patches argument to calculate metrics on random patches of images.

Positional Arguments

• dir1: Path to the first directory of images.
• dir2: Path to the second directory of images.

Options

• --metric: Metric to calculate (fd, fc, hd).
• --batch_size: Batch size for processing images.
• --num_of_images: Number of images to load from each directory.
• --as_gray: Load images as grayscale.
• --random_patches: Calculate metrics on random patches of images.
• --patch_size: Size of the random patches.
• --num_of_patch: Number of random patches to extract.
• --model: Pre-trained model to use as feature extractor (inceptionv3, resnet50v2, xception, densenet201, convnexttiny, efficientnetv2s).
• --verbose: Enable verbose output.

Example CLI Commands

To calculate the Frechet Distance between two sets of images, use the following command:

frechet-coefficient images/set1 images/set2 --metric fd

To calculate the Frechet Coefficient between two sets of images using the InceptionV3 model, use the following command:

frechet-coefficient images/set1 images/set2 --metric fc --model inceptionv3

To calculate the Hellinger Distance between two sets of images using random patches, use the following command:

frechet-coefficient images/set1 images/set2 --metric hd --random_patches --patch_size 128 --num_of_patch 10000

Python Code

You can also use python code to calculate similarity metrics between two sets of images.

import numpy as np
from typing import List
from frechet_coefficient import ImageSimilarityMetrics, load_images

# Initialize the ImageSimilarityMetrics class
ism = ImageSimilarityMetrics(model='inceptionv3', verbose=0)

images_1: List[np.ndarray] = load_images(path=...) # shape: (num_of_images, height, width, channels)
images_2: List[np.ndarray] = load_images(path=...) # shape: (num_of_images, height, width, channels)

# Calculate Frechet Distance
fd = ism.calculate_frechet_distance(images_1, images_2, batch_size=4)
# Calculate Frechet Coefficient
fc = ism.calculate_frechet_coefficient(images_1, images_2, batch_size=4)
# Calculate Hellinger Distance
hd = ism.calculate_hellinger_distance(images_1, images_2, batch_size=4)

# Calculate means vectors and covariance matrices
mean_1, cov_1 = ism.derive_mean_cov(images_1, batch_size=4)
mean_2, cov_2 = ism.derive_mean_cov(images_2, batch_size=4)

# Calculate metrics using mean vectors and covariance matrices
fd = ism.calculate_fd_with_mean_cov(mean_1, cov_1, mean_2, cov_2)
fc = ism.calculate_fc_with_mean_cov(mean_1, cov_1, mean_2, cov_2)
hd = ism.calculate_hd_with_mean_cov(mean_1, cov_1, mean_2, cov_2)

You can also calculate similarity metrics between two sets of images using random patches.

import numpy as np
from typing import List
from frechet_coefficient import ImageSimilarityMetrics, crop_random_patches, load_images

# Initialize the ImageSimilarityMetrics class
ism = ImageSimilarityMetrics(model='inceptionv3', verbose=0)

images_1: List[np.ndarray] = load_images(path=...) # shape: (num_of_images, height, width, channels)
images_2: List[np.ndarray] = load_images(path=...) # shape: (num_of_images, height, width, channels)

# Crop random patches from images
images_1_patches = crop_random_patches(images_1, size=(128, 128), num_of_patch=10000)
images_2_patches = crop_random_patches(images_2, size=(128, 128), num_of_patch=10000)

# Calculate Frechet Distance
fd = ism.calculate_frechet_distance(images_1_patches, images_2_patches, batch_size=4)
# Calculate Frechet Coefficient
fc = ism.calculate_frechet_coefficient(images_1_patches, images_2_patches, batch_size=4)
# Calculate Hellinger Distance
hd = ism.calculate_hellinger_distance(images_1_patches, images_2_patches, batch_size=4)

Metrics

• fd: Frechet Distance (with InceptionV3 model is equivalent to FID)
• fc: Frechet Coefficient
• hd: Hellinger Distance

The Hellinger Distance is numerically unstable for small datasets. The main reason is poorly estimated covariance matrices. To mitigate this issue, you can use the --random_patches argument to calculate metrics on random patches of images with a very high number of patches (e.g., 50000).

Models

• inceptionv3 - Input size: 299x299, Output size: 2048 - https://keras.io/api/applications/inceptionv3/
• resnet50v2 - Input size: 224x224, Output size: 2048 - https://keras.io/api/applications/resnet/
• xception - Input size: 224x224, Output size: 2048 - https://keras.io/api/applications/xception/
• densenet201 - Input size: 224x224, Output size: 1920 - https://keras.io/api/applications/densenet/
• convnexttiny - Input size: 224x224, Output size: 768 - https://keras.io/api/applications/convnext/
• efficientnetv2s - Input size: 384x384, Output size: 1280 - https://keras.io/api/applications/efficientnet/

Features

• Calculate Frechet Distance, Frechet Coefficient, and Hellinger Distance between two sets of images.
• Support for multiple pre-trained models.
• Option to calculate metrics on random patches of images.

Citation

If you use this package in your research, please consider citing the following paper:

• not available yet

License

This project is licensed under the MIT License. See the [LICENSE] file for details.