deepface/modules/preprocessing.py

import os
from typing import Union, Tuple
import base64
from pathlib import Path

# 3rd party
import numpy as np
import cv2
import requests


def load_image(img: Union[str, np.ndarray]) -> Tuple[np.ndarray, str]:
    """
    Load image from path, url, base64 or numpy array.
    Args:
        img: a path, url, base64 or numpy array.
    Returns:
        image (numpy array): the loaded image in BGR format
        image name (str): image name itself
    """

    # The image is already a numpy array
    if isinstance(img, np.ndarray):
        return img, "numpy array"

    if isinstance(img, Path):
        img = str(img)

    if not isinstance(img, str):
        raise ValueError(f"img must be numpy array or str but it is {type(img)}")

    # The image is a base64 string
    if img.startswith("data:image/"):
        return load_base64(img), "base64 encoded string"

    # The image is a url
    if img.lower().startswith("http://") or img.lower().startswith("https://"):
        return load_image_from_web(url=img), img

    # The image is a path
    if os.path.isfile(img) is not True:
        raise ValueError(f"Confirm that {img} exists")

    # image must be a file on the system then

    # image name must have english characters
    if img.isascii() is False:
        raise ValueError(f"Input image must not have non-english characters - {img}")

    img_obj_bgr = cv2.imread(img)
    # img_obj_rgb = cv2.cvtColor(img_obj_bgr, cv2.COLOR_BGR2RGB)
    return img_obj_bgr, img


def load_image_from_web(url: str) -> np.ndarray:
    """
    Loading an image from web
    Args:
        url: link for the image
    Returns:
        img (np.ndarray): equivalent to pre-loaded image from opencv (BGR format)
    """
    response = requests.get(url, stream=True, timeout=60)
    response.raise_for_status()
    image_array = np.asarray(bytearray(response.raw.read()), dtype=np.uint8)
    image = cv2.imdecode(image_array, cv2.IMREAD_COLOR)
    return image


def load_base64(uri: str) -> np.ndarray:
    """Load image from base64 string.

    Args:
        uri: a base64 string.

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

    encoded_data_parts = uri.split(",")

    if len(encoded_data_parts) < 2:
        raise ValueError("format error in base64 encoded string")

    # similar to find functionality, we are just considering these extensions
    if not (
        uri.startswith("data:image/jpeg")
        or uri.startswith("data:image/jpg")
        or uri.startswith("data:image/png")
    ):
        raise ValueError(f"input image can be jpg, jpeg or png, but it is {encoded_data_parts}")

    encoded_data = encoded_data_parts[1]
    nparr = np.fromstring(base64.b64decode(encoded_data), np.uint8)
    img_bgr = cv2.imdecode(nparr, cv2.IMREAD_COLOR)
    # img_rgb = cv2.cvtColor(img_bgr, cv2.COLOR_BGR2RGB)
    return img_bgr


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