Overlay photo speed, aperture, and ISO

overlay-exif.py

"""
Add legend with exposure speed, aperture, and ISO to top left of jpeg photo exif data.
Copies original exif data into output file.

Requires Python3.6, and some version of Pillow
"""

import argparse
from PIL import Image, ImageDraw, ImageColor, ImageFont
from PIL.ExifTags import TAGS, GPSTAGS


def parse_speed(exif_speed):
    assert exif_speed[0] == 1
    return f"{exif_speed[0]}/{exif_speed[1]}"


def parse_aperture(exif_aperture):
    assert exif_aperture[1] == 10
    return f"f{exif_aperture[0]/exif_aperture[1]}"


def parse_iso(exif_iso):
    return f"ISO {exif_iso}"


def main(in_file, out_file, comment=None):
    img = Image.open(in_file)
    exif = img._getexif()

    exif_data = {
        TAGS[tag] or GPSTAGS[tag]: value
        for tag, value in exif.items()
        if tag in TAGS or tag in GPSTAGS}

    assert exif_data['ExifVersion'] == b'0230'

    offset = min(img.height, img.width) // 20

    ImageDraw.Draw(img).multiline_text(
        (offset, offset),
        '\n'.join(filter(None, [
            comment,
            parse_speed(exif_data['ExposureTime']),
            parse_aperture(exif_data['FNumber']),
            parse_iso(exif_data['ISOSpeedRatings']),
        ])),
        ImageColor.getcolor("white", img.mode),
        font=ImageFont.truetype("arial.ttf", offset),
    )

    # exif takes a bytes object and not the dictionary from _getexif()
    img.save(out_file, "JPEG", exif=img.info['exif'])


if __name__ == "__main__":
    parser = argparse.ArgumentParser(__doc__)
    parser.add_argument("input_file", type=str)
    parser.add_argument("output_file", type=str)
    parser.add_argument("-c", "--comment", required=False, type=str)

    args = parser.parse_args()
    main(
        args.input_file,
        args.output_file,
        args.comment,
    )