Script to combine a set of images in "darken" or "lighten" mode, using PIL, rawpy, blend_modes

lighten.py

#!/usr/bin/env python3

import rawpy
from PIL import Image
from blend_modes import darken_only, lighten_only
from argparse import ArgumentParser
import numpy
import re
import sys

RAW_FORMATS = ['SRW']

parser = ArgumentParser()
parser.add_argument("filenames", metavar='FILE', nargs='+',
                  help="files to blend together")
parser.add_argument("-d", "--darken",
                  action="store_true", dest="darken", default=False,
                  help="darken instead of lighten images")
parser.add_argument("-g", "--gamma", dest="gamma", type=float, default=1.0,
                  help="raw import gamma")
parser.add_argument("-o", "--output", dest="output", default=None,
                  help="save result to OUTFILE", metavar="OUTFILE")
parser.add_argument("-q", "--quality", dest="quality", type=int, default=95,
                  help="jpeg file quality")
parser.add_argument("-s", "--silent",
                  action="store_false", dest="verbose", default=True,
                  help="don't print status messages to stdout")
args = parser.parse_args()

def extract_number(fn):
    try:
        return re.findall('\d+', fn)[-1]
    except IndexError:
        return None

def load_img(fn):
    if fn.split('.')[-1] in RAW_FORMATS:
        raw = rawpy.imread(fn)
        data = raw.postprocess(gamma=(args.gamma, args.gamma), no_auto_bright=True)
        image = Image.fromarray(data)
    else:
        image = Image.open(fn)
    return image.convert('RGBA')

f_first = args.filenames[0]
id_first = extract_number(f_first)
id_last = None

# Import background image
if args.verbose:
    print(f"Loading {f_first}...")
background_img_raw = load_img(f_first)  # RGBA image
background_img = numpy.array(background_img_raw)  # Inputs to blend_modes need to be numpy arrays.
merged_float = background_img.astype(float)  # Inputs to blend_modes need to be floats.

for f_next in args.filenames[1:]:
    id_last = extract_number(f_next)
    if args.verbose:
        print(f"Adding {f_next}...")
    # Import foreground image
    foreground_img_raw = load_img(f_next)  # RGBA image
    foreground_img = numpy.array(foreground_img_raw)  # Inputs to blend_modes need to be numpy arrays.
    foreground_img_float = foreground_img.astype(float)  # Inputs to blend_modes need to be floats.

    # Blend images
    if args.darken:
        merged_float = darken_only(merged_float, foreground_img_float, opacity=1.0)
    else:
        merged_float = lighten_only(merged_float, foreground_img_float, opacity=1.0)

# Convert blended image back into PIL image
blended_img = numpy.uint8(merged_float)  # Image needs to be converted back to uint8 type for PIL handling.
blended_img_raw = Image.fromarray(blended_img)  # Note that alpha channels are displayed in black by PIL by default.
                                                # This behavior is difficult to change (although possible).
                                                # If you have alpha channels in your images, then you should give
                                                # OpenCV a try.

if not args.output:
    # build name from extracted image number(s)
    if id_first and id_last:
        args.output = f"blended_{id_first}-{id_last}.jpg"
    elif id_first:
        args.output = f"blended_{id_first}.jpg"
    else:
        args.output = f"blended.jpg"

# Display blended image
if args.verbose:
    print(f"Saving {args.output}...")
blended_img_raw.convert('RGB').save(args.output, quality=args.quality, optimize=True, progressive=True)