Reducing the size of single or multiple PDF documents in GNU/Linux Bash and Python

#!/bin/sh
 
# http://www.alfredklomp.com/programming/shrinkpdf
# Licensed under the 3-clause BSD license:
#
# Copyright (c) 2014-2019, Alfred Klomp
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# 1. Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
# 3. Neither the name of the copyright holder nor the names of its contributors
#    may be used to endorse or promote products derived from this software
#    without specific prior written permission.
#
#
# Modified by Vivek Gite to suit my needs
#
shrink ()
{
	gs					\
	  -q -dNOPAUSE -dBATCH -dSAFER		\
	  -sDEVICE=pdfwrite			\
	  -dCompatibilityLevel=1.3		\
	  -dPDFSETTINGS=/screen			\
	  -dEmbedAllFonts=true			\
	  -dSubsetFonts=true			\
	  -dAutoRotatePages=/None		\
	  -dColorImageDownsampleType=/Bicubic	\
	  -dColorImageResolution=$3		\
	  -dGrayImageDownsampleType=/Bicubic	\
	  -dGrayImageResolution=$3		\
	  -dMonoImageDownsampleType=/Subsample	\
	  -dMonoImageResolution=$3		\
	  -sOutputFile="$2"			\
	  "$1"
}
 
check_smaller ()
{
	# If $1 and $2 are regular files, we can compare file sizes to
	# see if we succeeded in shrinking. If not, we copy $1 over $2:
	if [ ! -f "$1" -o ! -f "$2" ]; then
		return 0;
	fi
	ISIZE="$(echo $(wc -c "$1") | cut -f1 -d\ )"
	OSIZE="$(echo $(wc -c "$2") | cut -f1 -d\ )"
	if [ "$ISIZE" -lt "$OSIZE" ]; then
		echo "Input smaller than output, doing straight copy" >&2
		cp "$1" "$2"
	fi
}
 
usage ()
{
	echo "Reduces PDF filesize by lossy recompressing with Ghostscript."
	echo "Not guaranteed to succeed, but usually works."
	echo "  Usage: $1 infile [outfile] [resolution_in_dpi]"
}
 
IFILE="$1"
 
# Need an input file:
if [ -z "$IFILE" ]; then
	usage "$0"
	exit 1
fi
 
# Output filename defaults to "-" (stdout) unless given:
if [ ! -z "$2" ]; then
	OFILE="$2"
else
	OFILE="-"
fi
 
# Output resolution defaults to 72 unless given:
if [ ! -z "$3" ]; then
	res="$3"
else
	res="90"
fi
 
shrink "$IFILE" "$OFILE" "$res" || exit $?
 
check_smaller "$IFILE" "$OFILE"

./shrinkpdf.sh input.pdf output.pdf [resolution]

res="90"

shrink "$IFILE" "$OFILE" "$res" || exit $?

#!/bin/bash

shrink ()
{
    gs                          \
      -q -dNOPAUSE -dBATCH -dSAFER       \
      -sDEVICE=pdfwrite          \
      -dCompatibilityLevel=1.3       \
      -dPDFSETTINGS=/screen           \
      -dEmbedAllFonts=true            \
      -dSubsetFonts=true             \
      -dAutoRotatePages=/None        \
      -dColorImageDownsampleType=/Bicubic \
      -dColorImageResolution=$3      \
      -dGrayImageDownsampleType=/Bicubic  \
      -dGrayImageResolution=$3       \
      -dMonoImageDownsampleType=/Subsample \
      -dMonoImageResolution=$3       \
      -sOutputFile="$2"          \
      "$1"
}

check_smaller ()
{
    # If $1 and $2 are regular files, we can compare file sizes to
    # see if we succeeded in shrinking. If not, we copy $1 over $2:
    if [ ! -f "$1" ] || [ ! -f "$2" ]; then
        return 0
    fi
    ISIZE="$(wc -c < "$1")"
    OSIZE="$(wc -c < "$2")"
    if [ "$ISIZE" -lt "$OSIZE" ]; then
        echo "$1" >&2
    fi
}

usage ()
{
    echo "Reduces PDF filesize by lossy recompressing with Ghostscript."
    echo "Not guaranteed to succeed, but usually works."
    echo "  Usage: $1 infile [outfile] [resolution_in_dpi]"
}

if [ $# -lt 1 ]; then
    usage "$0"
    exit 1
fi

INPUT_FOLDER="$1"

if [ ! -d "$INPUT_FOLDER" ]; then
    echo "Error: $INPUT_FOLDER is not a directory."
    exit 1
fi

# Loop through all PDF files in the directory
for FILE in "$INPUT_FOLDER"/*.pdf; do
    [ -e "$FILE" ] || continue
    OUTPUT_FILE="${FILE%.pdf}_shrink.pdf"
    shrink "$FILE" "$OUTPUT_FILE" 90 || exit $?
    check_smaller "$FILE" "$OUTPUT_FILE"
done

shrink "$FILE" "$OUTPUT_FILE" 150 || exit $?

import os
import subprocess
import tkinter as tk
from tkinter import filedialog, messagebox
from tkinter.ttk import Progressbar

def shrink(input_file, output_file, resolution, progress_var):
    command = [
        "gs",
        "-q", "-dNOPAUSE", "-dBATCH", "-dSAFER",
        "-sDEVICE=pdfwrite",
        "-dCompatibilityLevel=1.3",
        "-dPDFSETTINGS=/screen",
        "-dEmbedAllFonts=true",
        "-dSubsetFonts=true",
        "-dAutoRotatePages=/None",
        "-dColorImageDownsampleType=/Bicubic",
        f"-dColorImageResolution={resolution}",
        "-dGrayImageDownsampleType=/Bicubic",
        f"-dGrayImageResolution={resolution}",
        "-dMonoImageDownsampleType=/Subsample",
        f"-dMonoImageResolution={resolution}",
        "-sOutputFile=" + output_file,
        input_file
    ]
    
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    while True:
        output = process.stderr.readline().decode().strip()
        if not output:
            break
        if output.startswith('Processing pages'):
            parts = output.split(' ')
            if len(parts) > 2:
                current_page = int(parts[2])
                progress_var.set((current_page / total_pages) * 100)
                root.update_idletasks()

def check_smaller(input_file, output_file):
    if not (os.path.isfile(input_file) and os.path.isfile(output_file)):
        return False
    isize = os.path.getsize(input_file)
    osize = os.path.getsize(output_file)
    return isize < osize

def browse_folder():
    folder_path = filedialog.askdirectory()
    if folder_path:
        input_folder_entry.delete(0, tk.END)
        input_folder_entry.insert(0, folder_path)

def process_folder():
    input_folder = input_folder_entry.get()
    if not os.path.isdir(input_folder):
        messagebox.showerror("Error", f"{input_folder} is not a directory.")
        return

    resolution = resolution_entry.get()
    try:
        resolution = int(resolution)
    except ValueError:
        messagebox.showerror("Error", "Resolution must be an integer.")
        return

    total_pdf_files = sum(1 for file_name in os.listdir(input_folder) if file_name.endswith(".pdf"))
    progress_var.set(0)
    for index, file_name in enumerate(os.listdir(input_folder)):
        if file_name.endswith(".pdf"):
            input_file = os.path.join(input_folder, file_name)
            output_file = os.path.join(input_folder, f"{os.path.splitext(file_name)[0]}_shrink.pdf")
            shrink(input_file, output_file, resolution, progress_var)
            if check_smaller(input_file, output_file):
                result_listbox.insert(tk.END, output_file)
        progress_var.set((index + 1) / total_pdf_files * 100)
        root.update_idletasks()

def close_application():
    root.destroy()

# GUI Setup
root = tk.Tk()
root.title("PDF Shrinker")

input_folder_label = tk.Label(root, text="Input Folder:")
input_folder_label.grid(row=0, column=0, padx=5, pady=5, sticky="e")

input_folder_entry = tk.Entry(root, width=50)
input_folder_entry.grid(row=0, column=1, padx=5, pady=5)

browse_button = tk.Button(root, text="Browse", command=browse_folder)
browse_button.grid(row=0, column=2, padx=5, pady=5)

resolution_label = tk.Label(root, text="Resolution (dpi):")
resolution_label.grid(row=1, column=0, padx=5, pady=5, sticky="e")

resolution_entry = tk.Entry(root)
resolution_entry.grid(row=1, column=1, padx=5, pady=5)

process_button = tk.Button(root, text="Process Folder", command=process_folder)
process_button.grid(row=2, column=0, columnspan=3, padx=5, pady=5)

progress_var = tk.DoubleVar()
progress_bar = Progressbar(root, variable=progress_var, maximum=100)
progress_bar.grid(row=3, column=0, columnspan=3, padx=5, pady=5)

close_button = tk.Button(root, text="Close", command=close_application)
close_button.grid(row=4, column=0, columnspan=3, padx=5, pady=5)

root.mainloop()