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"""
Part of the bsie module.
A copy of the license is provided with the project.
Author: Matthias Baumgartner, 2022
"""
# imports
import io
import typing
# external imports
import PIL.Image
# bsie imports
from bsie.utils import bsfs, node, ns
# inner-module imports
from . import base
# exports
__all__: typing.Sequence[str] = (
'Preview',
)
## code ##
class Preview(base.Extractor):
"""Extract previews."""
CONTENT_READER = 'bsie.reader.preview.Preview'
def __init__(self, max_sides: typing.Iterable[int]):
super().__init__(bsfs.schema.from_string(base.SCHEMA_PREAMBLE + '''
bsfs:Preview rdfs:subClassOf bsfs:Node .
bsfs:BinaryBlob rdfs:subClassOf bsfs:Literal .
bsfs:JPEG rdfs:subClassOf bsfs:BinaryBlob .
bse:preview rdfs:subClassOf bsfs:Predicate ;
rdfs:domain bsfs:File ;
rdfs:range bsfs:Preview ;
bsfs:unique "false"^^xsd:boolean .
bsp:width rdfs:subClassOf bsfs:Predicate ;
rdfs:domain bsfs:Preview ;
rdfs:range xsd:integer ;
bsfs:unique "true"^^xsd:boolean .
bsp:height rdfs:subClassOf bsfs:Predicate ;
rdfs:domain bsfs:Preview ;
rdfs:range xsd:integer ;
bsfs:unique "true"^^xsd:boolean .
bsp:asset rdfs:subClassOf bsfs:Predicate ;
rdfs:domain bsfs:Preview ;
rdfs:range bsfs:JPEG ;
bsfs:unique "true"^^xsd:boolean .
'''))
# initialize extra args
self.max_sides = set(max_sides)
def __eq__(self, other: typing.Any) -> bool:
return super().__eq__(other) \
and self.max_sides == other.max_sides
def __hash__(self) -> int:
return hash((super().__hash__(), tuple(sorted(self.max_sides))))
def extract(
self,
subject: node.Node,
content: typing.Callable[[int], PIL.Image.Image],
principals: typing.Iterable[bsfs.schema.Predicate],
) -> typing.Iterator[typing.Tuple[node.Node, bsfs.schema.Predicate, typing.Any]]:
# check principals
if self.schema.predicate(ns.bse.preview) not in principals:
return
for max_side in self.max_sides:
# get the preview in the right resolution
img = content(max_side)
# convert the preview to jpeg
buffer = io.BytesIO()
img.save(buffer, format='jpeg')
# create a preview node
preview = node.Node(ns.bsfs.Preview,
ucid=bsfs.uuid.UCID.from_bytes(buffer.getvalue()),
size=max_side,
source=subject,
)
# yield triples
yield subject, self.schema.predicate(ns.bse.preview), preview
yield preview, self.schema.predicate(ns.bsp.width), img.width
yield preview, self.schema.predicate(ns.bsp.height), img.height
yield preview, self.schema.predicate(ns.bsp.asset), buffer.getvalue()
## EOF ##
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