scalebars.py

#!/usr/bin/python3
from sys import argv
from PIL import Image, ImageFont, ImageDraw
import exiftool


focus_distance_data = {
    ("OM Digital Solutions", "OM-5", 'OLYMPUS M.60mm F2.8 Macro'): {
        0.185: 304,
        0.22: 238,
        0.235: 201,
        0.255: 171,
        0.265: 145,
        0.285: 120,
        0.3: 97,
        0.31: 88,
        0.465: 72,
        0.535: 65
    }
}

def calculate_mm_size(filename):
    with exiftool.ExifToolHelper() as et:
        [metadata] = et.get_metadata([filename])
    make = metadata['EXIF:Make']
    model = metadata['EXIF:Model']
    lens = metadata['EXIF:LensModel']
    focus_distance = metadata['MakerNotes:FocusDistance']
    fdd = focus_distance_data[(make, model, lens)]

    if focus_distance in fdd:
        return fdd[focus_distance]

    if focus_distance > max(fdd):
        raise ValueError('Focus distance for this photo is out of range', focus_distance)

    fdd_items = sorted(fdd.items())
    for prev, next in zip(fdd_items, fdd_items[1:]):
        x1, y1 = prev
        x2, y2 = next
        if x1 < focus_distance < x2 :
            m = (y2 - y1) / (x2 - x1)
            b = y2 - m * x2
            return focus_distance * m + b

    raise ValueError('Focus distance for this photo is out of range', focus_distance)

filename = argv[1]

source_image = Image.open(argv[1]).convert("RGBA")

if len(argv) == 3:
    mm_size = int(argv[2])
else:
    mm_size = calculate_mm_size(filename)


if mm_size * 15 < source_image.width:
    word = '1cm'
    bar_width = mm_size * 10
else:
    word = '1mm'
    bar_width = mm_size


bar_height = source_image.height / 100

bar_margin = bar_height * 2

draw = ImageDraw.Draw(source_image)

draw.rectangle(
    ((source_image.width - bar_margin - bar_width,
      source_image.height - bar_margin - bar_height),
     (source_image.width - bar_margin,
      source_image.height - bar_margin)),
    fill="white"
)

font = ImageFont.truetype("Arial_Bold.ttf", int(source_image.height / 50))

word_width, word_height = font.getsize(word)

draw.text(
    (source_image.width - bar_margin - word_width,
     source_image.height - bar_margin - bar_height - word_height - source_image.height / 50 / 3),
    word,
    (255,255,255),
    font=font,
)

exif = source_image.info['exif']

name, ext = filename.split('.', 1)
source_image.convert("RGB").save(f'{name}-scalebar.{ext}', "JPEG", exif=exif)