Add a drop shadow effect to one or multiple images

shadowify.py

#!/usr/bin/env python3

from PIL import Image, ImageFilter
import argparse
from pathlib import Path
from typing import Optional

DEFAULT_POSTFIX = "-ds"


class BadArgsException(Exception):
    pass


# yoinked code
"""
Drop shadows with PIL.

Author: Kevin Schluff
License: Python license
"""


def dropShadow(
    image, offset=(5, 5), background=0xFFFFFF, shadow=0x444444, border=8, iterations=3
):
    """
  Add a gaussian blur drop shadow to an image.  
  
  image       - The image to overlay on top of the shadow.
  offset      - Offset of the shadow from the image as an (x,y) tuple.  Can be
                positive or negative.
  background  - Background colour behind the image.
  shadow      - Shadow colour (darkness).
  border      - Width of the border around the image.  This must be wide
                enough to account for the blurring of the shadow.
  iterations  - Number of times to apply the filter.  More iterations 
                produce a more blurred shadow, but increase processing time.
  """

    # Create the backdrop image -- a box in the background colour with a
    # shadow on it.
    totalWidth = image.size[0] + abs(offset[0]) + 2 * border
    totalHeight = image.size[1] + abs(offset[1]) + 2 * border
    back = Image.new(image.mode, (totalWidth, totalHeight), background)

    # Place the shadow, taking into account the offset from the image
    shadowLeft = border + max(offset[0], 0)
    shadowTop = border + max(offset[1], 0)
    back.paste(
        shadow,
        [shadowLeft, shadowTop, shadowLeft + image.size[0], shadowTop + image.size[1]],
    )

    # Apply the filter to blur the edges of the shadow.  Since a small kernel
    # is used, the filter must be applied repeatedly to get a decent blur.
    n = 0
    while n < iterations:
        back = back.filter(ImageFilter.BLUR)
        n += 1

    # Paste the input image onto the shadow backdrop
    imageLeft = border - min(offset[0], 0)
    imageTop = border - min(offset[1], 0)
    back.paste(image, (imageLeft, imageTop))

    return back


# end of code thievery


def single(src: Path, dest: Optional[Path], postfix: Optional[str]):
    print(f"Targeting: {src}")

    if not postfix:
        postfix = DEFAULT_POSTFIX

    if not src.exists() or not src.is_file():
        print(f"{src} is not a file")
        raise BadArgsException()

    if not dest:
        if "." not in str(src.name):
            dest_path = str(src.resolve().parent.joinpath(src.name + postfix))
        else:
            partition = src.name.rsplit(".", 1)
            dest_path = str(
                src.resolve().parent.joinpath(
                    partition[0] + postfix + "." + partition[1]
                )
            )
        print(f"Determined destination: {dest_path}")

    else:
        dest_path = str(dest)
        print(f"Using destination: {dest_path}")

    image = Image.open(str(src))
    print("Computing...")
    new_image = dropShadow(image)
    print("Saving...")
    new_image.save(dest_path, "PNG")


def recurse(srcdir: Path, destdir: Optional[Path], postfix: Optional[str]):
    if not postfix:
        postfix = DEFAULT_POSTFIX
    if not srcdir.exists() or not srcdir.is_dir():
        print(f"{srcdir} is not a directory")
        raise BadArgsException()

    if not destdir:
        destdir = srcdir

    if destdir.exists() and destdir.is_file():
        print(f"{destdir} already exists and is a file, not a directory")
    else:
        if not destdir.exists():
            destdir.mkdir()

    print(f"Destination directory: {destdir}")
    print(f"Finding images to modify:")
    for src in srcdir.iterdir():
        print("")
        if not src.is_file():
            print(f"Skipping sub directory: {src.name}")
            continue
        if "." in src.name:
            partition = src.name.rsplit(".", 1)
            if partition[0].endswith(postfix):
                print(f"Skipping already converted: {partition[0]}")
                continue
        if src.suffix.lower() in [".png"]:
            # postfix has to be preapplied
            partition = src.name.rsplit(".", 1)
            dest_path = src.resolve().parent.joinpath(
                partition[0] + postfix + "." + partition[1]
            )
            single(src.resolve(), dest_path, None)
        else:
            # TODO: ability to customize png
            print(f"Unsupported file type: {src.name}. skipping")


if __name__ == "__main__":
    import sys

    parser = argparse.ArgumentParser()
    parser.add_argument("-s", "--src", type=str, help="A single source file")
    parser.add_argument(
        "-S", "--srcdir", type=str, help="A directory to recursively convert"
    )
    parser.add_argument("-d", "--dest", type=str, help="A single destination location")
    parser.add_argument(
        "-p",
        "--postfix",
        type=str,
        help="string to add to source base name if no dest is specified",
    )
    parser.add_argument(
        "-D",
        "--destdir",
        type=str,
        help="A directory to output recrusively converted files to",
    )

    args = parser.parse_args()
    if args.dest:
        dest = Path(args.dest)
    else:
        dest = None
    if args.destdir:
        destdir = Path(args.destdir)
    else:
        destdir = None
    try:
        if args.src:
            single(Path(args.src), dest, args.postfix)
        elif args.srcdir:
            recurse(Path(args.srcdir), destdir, args.postfix)
        else:
            parser.print_help()
    except BadArgsException as e:
        parser.print_help()
        sys.exit(1)

    # dropShadow(image, background=0xEEEEEE, shadow=0x444444, offset=(0, 5)).show()

usage: shadowify.py [-h] [-s SRC] [-S SRCDIR] [-d DEST] [-p POSTFIX] [-D DESTDIR]

optional arguments:
  -h, --help            show this help message and exit
  -s SRC, --src SRC     A single source file
  -S SRCDIR, --srcdir SRCDIR
                        A directory to recursively convert
  -d DEST, --dest DEST  A single destination location
  -p POSTFIX, --postfix POSTFIX
                        string to add to source base name if no dest is specified
  -D DESTDIR, --destdir DESTDIR
                        A directory to output recrusively converted files to

As of now, only .png files are supported as the save format is hardcoded. This can be easily modified.by changing lines 103 and 131