remove exif from jpg without PIL

remove_exif.py

"""
This code is based on https://github.com/AzadKurt/pexif written by AzadKurt
"""


def remove_exif(img_bytes: bytes) -> bytes:
    """
    returns the bytes of the image without exif

    :param img_bytes: image bytes including exif
    :return: image bytes without exif
    """
    exif_start = get_exif_sig_start(img_bytes)
    if not exif_start:
        return img_bytes

    img_size = len(img_bytes)
    exif_data_size = ((img_bytes[exif_start + 2] << 8) | img_bytes[exif_start + 3]) + 2
    # + 2 to include exif marker 0xFFE1

    i = exif_start + exif_data_size
    while not (img_bytes[i] == 0xFF and img_bytes[i + 1] == 0xDB):
        i += ((img_bytes[i + 2] << 8) | img_bytes[i + 3]) + 2  # skip to next marker

    new_size = img_size - i + 20  # + 20 because of the 20 jfif bytes
    purged = init_basic_jfif(new_size)
    jfif_difference = i - 20
    for ii in range(i, img_size):
        purged[ii - jfif_difference] = img_bytes[ii]

    return bytes(purged)


def get_exif_sig_start(img_bytes: bytes) -> int:
    """
    find the starting position of exif
    if there is no exif returns 0

    :param img_bytes: image bytes
    :return: index of image
    """
    if not (img_bytes[0] == 0xFF and img_bytes[1] == 0xD8):
        return 0

    for i in range(2, len(img_bytes)):
        if img_bytes[i] == 0xFF:
            marker = img_bytes[i + 1]
            if marker == 0xDB:  # 0xFFDB marks the beginning of the quantization table
                return 0
            if marker == 0xE1:
                return i

            # if another marker that is not the exif marker is present,
            # jump forward by the specified data size of the current marker
            if (marker & 0xF0) == 0xE0:
                i += ((img_bytes[i + 2] << 8) | img_bytes[i + 3]) + 1
                # + 1 because the two bytes that specify the data size are
                # included and + 1 together with i++ results in an increase of 2
    return 0


def init_basic_jfif(size):
    """
    these bytes make up the beginning of a basic jpg in the jfif format
    for an explanation as to what these specific bytes mean, visit
    https://www.ccoderun.ca/programming/2017-01-31_jpeg/ or
    http://web.archive.org/web/20200929185628/https://www.ccoderun.ca/programming/2017-01-31_jpeg/ if necessary

    :param size: size of image
    :return: allocated list of image bytes
    """
    purged = [0] * size
    purged[0] = 0xFF
    purged[1] = 0xD8
    purged[2] = 0xFF
    purged[3] = 0xE0
    purged[4] = 0x00
    purged[5] = 0x10
    purged[6] = 0x4A
    purged[7] = 0x46
    purged[8] = 0x49
    purged[9] = 0x46
    purged[10] = 0x00
    purged[11] = 0x01
    purged[12] = 0x01
    purged[13] = 0x00
    purged[14] = 0x00
    purged[15] = 0x01
    purged[16] = 0x00
    purged[17] = 0x01
    purged[18] = 0x00
    purged[19] = 0x00
    return purged


if __name__ == '__main__':
    with open('in.jpg', 'rb') as f:
        raw = f.read()
        
    with open('out.jpg', 'wb') as f:
        f.write(remove_exif(raw))