# -*- coding: utf-8 -*-
"""This module contains the core functions of the pdfebc program. These consist mostly
of functions that manipulate PDF files and the file system.
.. module:: core
:platform: Unix
:synopsis: Core functions for pdfebc.
.. moduleauthor:: Simon Larsén <slarse@kth.se>
"""
import os
import sys
import subprocess
from . import utils
BYTES_PER_MEGABYTE = 1024**2
FILE_SIZE_LOWER_LIMIT = BYTES_PER_MEGABYTE
PDF_EXTENSION = ".pdf"
COMPRESSING_MULTIPLE = """Source directory: '{}'
Output directory: '{}'
Found '{}' PDF files. Starting compression ..."""
ALL_FILES_DONE = """All files done!
Results saved to '{}'"""
COMPRESSING = "Compressing '{}' ..."
FILE_DONE = "File done! Result saved to '{}'"
NOT_COMPRESSING = """Not compressing '{}'
Reason: Actual file size is {} bytes,
lower limit for compression is {} bytes"""
GS_NOT_INSTALLED = """Ghostscript not installed or not aliased to '{}'.
Exiting ..."""
[docs]def get_pdf_filenames_at(source_directory):
"""Find all PDF files in the specified directory.
Args:
source_directory (str): The source directory.
Returns:
list(str): Filepaths to all PDF files in the specified directory.
Raises:
ValueError
"""
if not os.path.isdir(source_directory):
raise ValueError("%s is not a directory!" % source_directory)
return [os.path.join(source_directory, filename)
for filename in os.listdir(source_directory)
if filename.endswith(PDF_EXTENSION)]
[docs]def compress_pdf(filepath, output_path, ghostscript_binary, status_callback=None):
"""Compress a single PDF file.
Args:
filepath (str): Path to the PDF file.
output_path (str): Output path.
ghostscript_binary (str): Name/alias of the Ghostscript binary.
status_callback (function): A callback function for passing status messages to a view.
Raises:
ValueError
"""
if not filepath.endswith(PDF_EXTENSION):
raise ValueError("Filename must end with .pdf!\n%s does not." % filepath)
try:
file_size = os.stat(filepath).st_size
if file_size < FILE_SIZE_LOWER_LIMIT:
utils.if_callable_call_with_formatted_string(status_callback, NOT_COMPRESSING,
filepath, file_size, FILE_SIZE_LOWER_LIMIT)
process = subprocess.Popen(['cp', filepath, output_path])
else:
utils.if_callable_call_with_formatted_string(status_callback, COMPRESSING, filepath)
process = subprocess.Popen(
[ghostscript_binary, "-sDEVICE=pdfwrite",
"-dCompatabilityLevel=1.4", "-dPDFSETTINGS=/ebook",
"-dNOPAUSE", "-dQUIET", "-dBATCH",
"-sOutputFile=%s" % output_path, filepath]
)
except FileNotFoundError:
utils.if_callable_call_with_formatted_string(status_callback, GS_NOT_INSTALLED,
ghostscript_binary)
sys.exit(1)
process.communicate()
utils.if_callable_call_with_formatted_string(status_callback, FILE_DONE, output_path)
[docs]def compress_multiple_pdfs(source_directory, output_directory, ghostscript_binary, status_callback=None):
"""Compress all PDF files in the current directory and place the output in the given output directory.
Args:
source_directory (str): Filepath to the source directory.
output_directory (str): Filepath to the output directory.
ghostscript_binary (str): Name of the Ghostscript binary.
status_callback (function): A callback function for passing status messages to a view.
Returns:
list(str): paths to outputs.
"""
source_paths = get_pdf_filenames_at(source_directory)
out_paths = list()
utils.if_callable_call_with_formatted_string(status_callback, COMPRESSING_MULTIPLE,
source_directory, output_directory, len(source_paths))
for source_path in source_paths:
output = os.path.join(output_directory, os.path.basename(source_path))
out_paths.append(output)
compress_pdf(source_path, output, ghostscript_binary, status_callback)
utils.if_callable_call_with_formatted_string(status_callback, ALL_FILES_DONE, output_directory)
return out_paths