Paste a screenshot on top of a template image to produce an output image with a drop shadow

process.py

#!/usr/bin/env python3

# This script pastes the input image on top of the template image and writes out
# a new file. The reference template image includes a drop shadow.
#
# To get this script working on macOS, install the following dependencies:
#
#   $ brew install pngquant
#   $ python3 -m pip install Pillow pngquant
#
# Because this script was designed to work on macOS, the image sizes have been
# doubled to account for retina resolution.
#
# Input images must be exactly 2400 by 1400 pixels.


import sys
import pathlib

from PIL import Image
import pngquant

if len(sys.argv) != 3:
    print(f"Usage: {sys.argv[0]} TEMPLATE_IMG INPUT_IMG")
    sys.exit(1)

template_filename = sys.argv[1]
input_filename = sys.argv[2]

template_img = Image.open(template_filename)
input_img = Image.open(input_filename)

# Check template image is correct size
if template_img.width != 2560 or template_img.height != 1560:
    print(f"ERROR: Incorrect template image size")
    sys.exit(1)

# Check input image is correct size
if input_img.width != 2400 or input_img.height != 1400:
    print(f"ERROR: Incorrect input image size")
    sys.exit(1)

template_img.paste(input_img, (80, 80))

input_path = pathlib.Path(input_filename)
new_stem = f"{input_path.stem}-out"
output_path = input_path.with_stem(new_stem)

template_img.save(output_path, optimize=True)

print(f"Saved: {output_path}")