Store custom data in .tif EXIF metadata using Python

tif-exif.py

from PIL import Image
# Use the UserComment field, since manufacturers et al. leave it empty
# https://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif/usercomment.html
EXIF_USERCOMMENT = 37510 

def write_exif(src_path, dst_path, json_dict):
    """Write json (dictionary)
    """
    write_exif_string(src_path, dst_path, json.dumps(json_dict))

def write_exif_string(src_path, dst_path, string):
    """Write a string
    """
    image = Image.open(src_path)
    image.tag[EXIF_USERCOMMENT] = string
    image.save(dst_path, tiffinfo=image.tag)

def read_exif(path):
    """Returns json (dictionary)
    """
    return json.loads(read_exif_string(path))

def read_exif_string(path):
    """Returns a string
    """
    with Image.open(path) as image:
        return image.tag[EXIF_USERCOMMENT][0]

Example:

    path = "/path/to/photo.tif"

    data = {
        "fruit" : "pineapple"
    }

    write_exif(path, path, data)
    print(read_exif(path)["fruit"])