imresize

#!/usr/bin/env python
"""imresize: resize image files (typically for email use).

This script makes a copy of each given file with specified size and jpeg
quality, tagged with a suffix (it doesn't overwrite the input files).
Without options, the defaults try to give small sized files for email use.
See below for a description of options and their default values. This script
is basically just a wrapper around ImageMagick's convert.
"""

__author__ = "Fernando Perez"
__email__ = "fernando.perez@berkeley.edu"
__version__ = "0.3"
__date__ = "2017-04-16"
__license__ = "BSD"

# ***************************************************************************
# Standard library modules
import os
import sys

from argparse import ArgumentParser
from pathlib import Path
from subprocess import check_call


def parse_args(argv=None):
    """Parse command-line args and return resulting Namespace.
    """
    parser = ArgumentParser(description=__doc__)
    addarg = parser.add_argument
    addarg(
        "--size",
        type=str,
        nargs="?",
        default="1280x1280",
        help="size (bounding box) of final images, specified as HHxVV, "
        "e.g. 1280x1280.",
    )
    addarg(
        "--quality",
        type=int,
        nargs="?",
        default=65,
        help="quality parameter for jpeg compression, according to "
        "ImageMagick conventions (a number in the 0-100 range)",
    )
    addarg(
        "--suffix",
        type=str,
        nargs="?",
        default="_sm",
        help="suffix appended to each file generated. If foo.jpg is an "
        "input file, then foo_sm.jpg will be the resized copy.",
    )
    addarg(
        "--outdir",
        type=Path,
        nargs="?",
        default=Path("."),
        help="output directory.  If it doesn't exist, it will be "
        "automatically created with a call equivalent to `mkdir -p`",
    )
    addarg("filename", nargs="+")
    return parser.parse_args(argv)


def main(argv=None):
    """Main script entry point.
    """
    args = parse_args(argv)
    print(f"args:{args}")  # dbg
    # a few convenient shortcuts
    size = args.size
    quality = args.quality
    outdir = args.outdir

    if outdir.exists():
        if not outdir.is_dir():
            raise OSError(f"<{outdir}> must be a directory!")
    else:
        if outdir.resolve() != Path(".").resolve():
            print("Making directory:", outdir)
            outdir.mkdir(parents=True, exist_ok=True)

    cmd = ["convert", "-quality", str(quality), "-size", size, "-resize", size]

    print(f"Resizing images. Output size: {size}, quality: {quality}.")

    for fname in map(Path, args.filename):
        if not fname.is_file():
            print(f"*** File {fname} does not exist, skipping.")
            continue
        root, ext = os.path.splitext(fname)
        fname_out = outdir.joinpath(root + args.suffix + ext)
        print(fname, "->", fname_out, end="")
        check_call(cmd + [fname, fname_out])
        insize = fname.stat().st_size
        outsize = fname_out.stat().st_size
        reduction = 100 - 100 * outsize / insize
        print(
            f": {insize/1024:g}K -> {outsize/1024:g}K, "
            f"({round(reduction)}% reduction)"
        )

    return 0


if __name__ == "__main__":
    sys.exit(main())