modules/preprocessing.py

# built-in dependencies
from typing import Tuple

# 3rd party
import numpy as np
import cv2

# project dependencies
from deepface.commons import package_utils


tf_major_version = package_utils.get_tf_major_version()
if tf_major_version == 1:
    from keras.preprocessing import image
elif tf_major_version == 2:
    from tensorflow.keras.preprocessing import image


def normalize_input(img: np.ndarray, normalization: str = "base") -> np.ndarray:
    """Normalize input image.

    Args:
        img (numpy array): the input image.
        normalization (str, optional): the normalization technique. Defaults to "base",
        for no normalization.

    Returns:
        numpy array: the normalized image.
    """

    # issue 131 declares that some normalization techniques improves the accuracy

    if normalization == "base":
        return img

    # @trevorgribble and @davedgd contributed this feature
    # restore input in scale of [0, 255] because it was normalized in scale of
    # [0, 1] in preprocess_face
    img *= 255

    if normalization == "raw":
        pass  # return just restored pixels

    elif normalization == "Facenet":
        mean, std = img.mean(), img.std()
        img = (img - mean) / std

    elif normalization == "Facenet2018":
        # simply / 127.5 - 1 (similar to facenet 2018 model preprocessing step as @iamrishab posted)
        img /= 127.5
        img -= 1

    elif normalization == "VGGFace":
        # mean subtraction based on VGGFace1 training data
        img[..., 0] -= 93.5940
        img[..., 1] -= 104.7624
        img[..., 2] -= 129.1863

    elif normalization == "VGGFace2":
        # mean subtraction based on VGGFace2 training data
        img[..., 0] -= 91.4953
        img[..., 1] -= 103.8827
        img[..., 2] -= 131.0912

    elif normalization == "ArcFace":
        # Reference study: The faces are cropped and resized to 112×112,
        # and each pixel (ranged between [0, 255]) in RGB images is normalised
        # by subtracting 127.5 then divided by 128.
        img -= 127.5
        img /= 128
    else:
        raise ValueError(f"unimplemented normalization type - {normalization}")

    return img


def resize_image(img: np.ndarray, target_size: Tuple[int, int]) -> np.ndarray:
    """
    Resize an image to expected size of a ml model with adding black pixels.
    Args:
        img (np.ndarray): pre-loaded image as numpy array
        target_size (tuple): input shape of ml model
    Returns:
        img (np.ndarray): resized input image
    """
    factor_0 = target_size[0] / img.shape[0]
    factor_1 = target_size[1] / img.shape[1]
    factor = min(factor_0, factor_1)

    dsize = (
        int(img.shape[1] * factor),
        int(img.shape[0] * factor),
    )
    img = cv2.resize(img, dsize)

    diff_0 = target_size[0] - img.shape[0]
    diff_1 = target_size[1] - img.shape[1]

    # Put the base image in the middle of the padded image
    img = np.pad(
        img,
        (
            (diff_0 // 2, diff_0 - diff_0 // 2),
            (diff_1 // 2, diff_1 - diff_1 // 2),
            (0, 0),
        ),
        "constant",
    )

    # double check: if target image is not still the same size with target.
    if img.shape[0:2] != target_size:
        img = cv2.resize(img, target_size)

    # make it 4-dimensional how ML models expect
    img = image.img_to_array(img)
    img = np.expand_dims(img, axis=0)

    if img.max() > 1:
        img = (img.astype(np.float32) / 255.0).astype(np.float32)

    return img