Proof of Concept for OpenRaster-based "Use external editor" option

openraster_test.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Proof of concept code for generating and opening an OpenRaster image in the
user's preferred OpenRaster editor.
"""

__author__ = "Stephan Sokolow (deitarion/SSokolow)"
__appname__ = "OpenRaster Proof of Concept"
__version__ = "0.1"
__license__ = "MIT"

import logging
import os
import subprocess
import sys
import tempfile
import zipfile
import xml.etree.ElementTree as ET

from PIL import Image

log = logging.getLogger(__name__)


def to_ora(img2img_src, mask=None, out_path=None):
    """Combine the given file and, optionally, a pre-existing mask into an
    OpenRaster file suitable for a "use external editor" option.
    """
    outdir = os.path.dirname(out_path) if out_path else None
    img = Image.open(img2img_src)
    try:
        (ora_fd, ora_path) = tempfile.mkstemp(dir=outdir,
            prefix='ext_ed-', suffix='.ora')
        with open(ora_fd, 'wb') as fh:
            with zipfile.ZipFile(fh,
                    mode='w',
                    # ORA supports STORE or DEFLATE but, since we're using this
                    # to exchange data between two apps on the same machine
                    # through a transient file, don't waste the CPU time doing
                    # DEFLATE compression beyond what's already internal to the
                    # layer files we're embedding.
                    compression=zipfile.ZIP_STORED) as ora_zh:

                # Required pseudo-"magic number". Must always be STOREd
                ora_zh.writestr('mimetype', 'image/openraster',
                                zipfile.ZIP_STORED)

                # img2img source
                #
                # Write it as mergedimage.png to save space and time. The spec
                # says it's just convention that the layers are under /data
                # and mergedimage.png is mandatory, so let's just show the
                # img2img layer.
                with ora_zh.open('mergedimage.png', 'w') as fh:
                    img.save(fh, format='png')

                # Mask
                # (Empty for proof of concept, but would be
                # persisted in practice)
                with ora_zh.open('data/mask.png', 'w') as fh:
                    if mask:
                        Image.open(mask).save(fh, format='png')
                    else:
                        Image.new('1', img.size).save(fh, format='png')

                # Layer stack definition
                with ora_zh.open('stack.xml', 'w') as fh:
                    image_node = ET.Element('image')
                    image_node.set('version', '0.0.3')
                    image_node.set('w', str(img.size[0]))
                    image_node.set('h', str(img.size[1]))
                    stack_node = ET.SubElement(image_node, 'stack')
                    ET.SubElement(stack_node, 'layer', name='Mask',
                        src='data/mask.png', opacity=str(0.5), selected="true")
                    ET.SubElement(stack_node, 'layer', name='Base Image',
                        src='mergedimage.png')
                    stack_xml = ET.ElementTree(image_node)
                    stack_xml.write(fh, encoding='UTF-8', xml_declaration=True)

                # We create a technically-usable thumbnail because *some* kind
                # of thumbnail is required by the ORA spec and we don't want to
                # risk confusing the user if it displays the cached thumbnail
                # somewhere.
                #
                # Must be written after stack.xml since it modifies the image
                # in-place before the dimensions are read.
                #
                # TODO: Check if it's possible to request to prefer reuse of
                # any embedded thumbnail in the source image.
                with ora_zh.open('Thumbnails/thumbnail.png', 'w') as fh:
                    img.thumbnail((128, 128), resample=0)
                    img.save(fh, 'png')
    except BaseException:
        os.remove(ora_path)
    else:
        if out_path:
            os.rename(ora_path, out_path)
            return out_path
        else:
            return ora_path

# TODO: from_ora


def process_arg(path):
    ora_path = to_ora(path)
    print("Generated .ora file at ", ora_path)

    if os.name == 'nt':
        os.startfile(ora_path.replace('/', '\\'))
    elif sys.platform == 'darwin':
        subprocess.call(('open', ora_path))
    else:
        subprocess.call(('xdg-open', ora_path))


def main():
    """The main entry point, compatible with setuptools entry points."""
    from argparse import ArgumentParser, RawDescriptionHelpFormatter
    parser = ArgumentParser(formatter_class=RawDescriptionHelpFormatter,
        description=__doc__.replace('\r\n', '\n').split('\n--snip--\n')[0])
    parser.add_argument('-V', '--version', action='version',
        version="%%(prog)s v%s" % __version__)
    parser.add_argument('-v', '--verbose', action="count",
        default=2, help="Increase the verbosity. Use twice for extra effect.")
    parser.add_argument('-q', '--quiet', action="count",
        default=0, help="Decrease the verbosity. Use twice for extra effect.")
    parser.add_argument('path', action="store", nargs="+",
        help="Path to operate on")
    # Reminder: %(default)s can be used in help strings.

    args = parser.parse_args()

    # Set up clean logging to stderr
    log_levels = [logging.CRITICAL, logging.ERROR, logging.WARNING,
                  logging.INFO, logging.DEBUG]
    args.verbose = min(args.verbose - args.quiet, len(log_levels) - 1)
    args.verbose = max(args.verbose, 0)
    logging.basicConfig(level=log_levels[args.verbose],
                        format='%(levelname)s: %(message)s')

    for path in args.path:
        process_arg(path)


if __name__ == '__main__':  # pragma: nocover
    main()

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