Terralego/django-terra-geocrud

import hashlib
import logging

from sorl.thumbnail.base import ThumbnailBackend
from sorl.thumbnail.conf import settings, defaults as default_settings
from sorl.thumbnail.images import ImageFile, DummyImageFile
from sorl.thumbnail import default
from terra_geocrud.properties.files import get_storage

logger = logging.getLogger(__name__)


class ThumbnailDataFileBackend(ThumbnailBackend):

    def get_thumbnail(self, file_, geometry_string, **options):
        """
        Returns thumbnail as an ImageFile instance for file with geometry and
        options given. First it will try to get it from the key value store,
        secondly it will create it.

        Override from ThumbnailBackend to use different storage backend for image source
        """
        logger.debug('Getting thumbnail for file [%s] at [%s]', file_, geometry_string)

        if file_:
            source = ImageFile(file_, storage=get_storage())
        else:
            raise ValueError('falsey file_ argument in get_thumbnail()')

        # preserve image filetype
        if settings.THUMBNAIL_PRESERVE_FORMAT:
            options.setdefault('format', self._get_format(source))

        for key, value in self.default_options.items():
            options.setdefault(key, value)

        # For the future I think it is better to add options only if they
        # differ from the default settings as below. This will ensure the same
        # filenames being generated for new options at default.
        for key, attr in self.extra_options:
            value = getattr(settings, attr)
            if value != getattr(default_settings, attr):
                options.setdefault(key, value)

        try:
            source_image = default.engine.get_image(source)
            options['hash'] = hashlib.md5(source_image.tobytes()).hexdigest()
        except IOError:
            pass

        name = self._get_thumbnail_filename(source, geometry_string, options)
        thumbnail = ImageFile(name, default.storage)
        cached = default.kvstore.get(thumbnail)

        if cached and cached.exists():
            return cached

        # We have to check exists() because the Storage backend does not
        # overwrite in some implementations.
        if settings.THUMBNAIL_FORCE_OVERWRITE or not thumbnail.exists():
            try:
                source_image = default.engine.get_image(source)
            except IOError as e:
                logger.exception(e)
                if settings.THUMBNAIL_DUMMY:
                    return DummyImageFile(geometry_string)
                else:
                    # if S3Storage says file doesn't exist remotely, don't try to
                    # create it and exit early.
                    # Will return working empty image type; 404'd image
                    logger.warning(
                        'Remote file [%s] at [%s] does not exist',
                        file_, geometry_string,
                    )
                    return thumbnail

            # We might as well set the size since we have the image in memory
            image_info = default.engine.get_image_info(source_image)
            options['image_info'] = image_info
            size = default.engine.get_image_size(source_image)
            source.set_size(size)

            try:
                self._create_thumbnail(source_image, geometry_string, options,
                                       thumbnail)
                self._create_alternative_resolutions(source_image, geometry_string,
                                                     options, thumbnail.name)
            finally:
                default.engine.cleanup(source_image)

        # If the thumbnail exists we don't create it, the other option is
        # to delete and write but this could lead to race conditions so I
        # will just leave that out for now.
        default.kvstore.get_or_set(source)
        default.kvstore.set(thumbnail, source)
        return thumbnail