Python code for compressing PDF files

pdf_compressor.py

#!/usr/bin/env python3
# Author: Theeko74
# Contributor(s): skjerns
# Oct, 2021
# MIT license -- free to use as you want, cheers.

"""
Simple python wrapper script to use ghoscript function to compress PDF files.

Compression levels:
    0: default - almost identical to /screen, 72 dpi images
    1: prepress - high quality, color preserving, 300 dpi imgs
    2: printer - high quality, 300 dpi images
    3: ebook - low quality, 150 dpi images
    4: screen - screen-view-only quality, 72 dpi images

Dependency: Ghostscript.
On MacOSX install via command line `brew install ghostscript`.
"""

import argparse
import os.path
import shutil
import subprocess
import sys


def compress(input_file_path, output_file_path, power=0):
    """Function to compress PDF via Ghostscript command line interface"""
    quality = {
        0: "/default",
        1: "/prepress",
        2: "/printer",
        3: "/ebook",
        4: "/screen"
    }

    # Basic controls
    # Check if valid path
    if not os.path.isfile(input_file_path):
        print("Error: invalid path for input PDF file.", input_file_path)
        sys.exit(1)

    # Check compression level
    if power < 0 or power > len(quality) - 1:
        print("Error: invalid compression level, run pdfc -h for options.", power)
        sys.exit(1)

    # Check if file is a PDF by extension
    if input_file_path.split('.')[-1].lower() != 'pdf':
        print(f"Error: input file is not a PDF.", input_file_path)
        sys.exit(1)

    gs = get_ghostscript_path()
    print("Compress PDF...")
    initial_size = os.path.getsize(input_file_path)
    subprocess.call(
        [
            gs,
            "-sDEVICE=pdfwrite",
            "-dCompatibilityLevel=1.4",
            "-dPDFSETTINGS={}".format(quality[power]),
            "-dNOPAUSE",
            "-dQUIET",
            "-dBATCH",
            "-sOutputFile={}".format(output_file_path),
            input_file_path,
        ]
    )
    final_size = os.path.getsize(output_file_path)
    ratio = 1 - (final_size / initial_size)
    print("Compression by {0:.0%}.".format(ratio))
    print("Final file size is {0:.5f}MB".format(final_size / 1000000))
    print("Done.")


def get_ghostscript_path():
    gs_names = ["gs", "gswin32", "gswin64"]
    for name in gs_names:
        if shutil.which(name):
            return shutil.which(name)
    raise FileNotFoundError(
        f"No GhostScript executable was found on path ({'/'.join(gs_names)})"
    )


def main():
    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument("input", help="Relative or absolute path of the input PDF file")
    parser.add_argument("-o", "--out", help="Relative or absolute path of the output PDF file")
    parser.add_argument("-c", "--compress", type=int, help="Compression level from 0 to 4")
    parser.add_argument("-b", "--backup", action="store_true", help="Backup the old PDF file")
    parser.add_argument("--open", action="store_true", default=False, help="Open PDF after compression")
    args = parser.parse_args()

    # In case no compression level is specified, default is 2 '/ printer'
    if not args.compress:
        args.compress = 2
    # In case no output file is specified, store in temp file
    if not args.out:
        args.out = "temp.pdf"

    # Run
    compress(args.input, args.out, power=args.compress)

    # In case no output file is specified, erase original file
    if args.out == "temp.pdf":
        if args.backup:
            shutil.copyfile(args.input, args.input.replace(".pdf", "_BACKUP.pdf"))
        shutil.copyfile(args.out, args.input)
        os.remove(args.out)

    # In case we want to open the file after compression
    if args.open:
        if args.out == "temp.pdf" and args.backup:
            subprocess.call(["open", args.input])
        else:
            subprocess.call(["open", args.out])


if __name__ == "__main__":
    main()