photo_config.py

#!/home/patrick/Documents/programming/python_projects/photo-processing/bin/python3
# -*- coding: utf-8 -*-
"""
A series of declarations about external programs, used by other scripts in the
photo-processing scripts collection.

This program comes with ABSOLUTELY NO WARRANTY. Use at your own risk.

This program is part of Patrick Mooney's photo postprocessing scripts; the
complete set can be found at https://github.com/patrick-brian-mooney/photo-processing.
All programs in that collection are copyright 2015-2019 by Patrick Mooney; they
are free software released under the GNU GPL, either version 3 or (at your
option) any later version. See the file LICENSE.md for details.

The latest version of these scripts can always be found at
    https://github.com/patrick-brian-mooney/photo-processing
"""


import os, platform, shlex, subprocess, sys

import PIL  # I'd rather have this fail here, during setup checking, then in other places.


# The list of executable programs and their locations. Anything whose value is set to None will be searched for in
# the user's $PATH. If the executable is not in the $PATH, it can be set manually here. Note that some paths set here
# are not actually called by any of the photo-processing scripts directly: instead, they are called by bash scripts
# written by the photo-postprocessing scripts. They go here both for completeness's sake and because this forces a
# check for their existence, which means that the relevant "program not installed" error is thrown early and
# intelligibly by this script, instead of cryptically when the user tries to (implicitly or explicitly) run the bash
# script. Note that other paths that need to be accessible can be set here manually or procedurally, too.
executables = {
    'exiftool': None,
    'exiftran': None,
    'luminance-hdr': None,
    'mogrify': None,
    'ffmpeg': None,
    'dcraw': None,
    'align_image_stack': None,
    'enfuse': None,
    'convert': None,
    'photo-processing': os.path.split(os.path.abspath(sys.argv[0]))[0],   # Well ... path to the folder containing the current script, actually. #FIXME: this will break if we move scripts around.
}


def executable_location(executable_name):
    """Return the known location for EXECUTABLE_NAME."""
    assert executable_name in executables, "ERROR: no known location for %s!\n\nIs the externals.py module properly set up?" % executable_name
    return executables[executable_name]


def populate_executables():
    """Populate the list of external executable programs."""
    for which_exec in executables:
        try:
            if executables[which_exec] is None:             # use POSIX `which` to locate the binary.
                executables[which_exec] = subprocess.check_output(['which', shlex.quote(which_exec)]).decode().strip()
        except BaseException as err:
            print("ERROR: unable to locate the program: %s." % which_exec)
            print("Please be sure it is installed and located in your system $PATH.")
            print("The system complained: %s" % err)
            sys.exit(1)


def startup():
    """Handle basic startup tasks: after making sure we're not running under Windows,
    populate the list of external programs. Doesn't do anything if the list is
    already initialized.
    * Assumes a terminal at least 80 chars wide.
    """
    if None in executables.values():
        if "windows" in platform.system().lower():
            print("ERROR: Patrick Mooney's photo-processing scripts do not run under Windows. With\nthe proper external programs and a little attention, though, they should run\nunder most Unix-like OSes.")
            sys.exit(1)
        populate_executables()


if __name__ == "__main__":
    startup()

    # If we haven't quit yet ...
    print("Successfully initialized program locations!")