Source code for properties.images

""" Image file property classes"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals

import base64
from io import BytesIO

import png
from six import string_types

from .basic import File

PNG_PREAMBLE = 'data:image/png;base64,'

[docs]class ImagePNG(File): """Property for PNG images **Available keywords** (in addition to those inherited from :ref:`Property <property>`): * **mode**: Opens the file in this mode. Must be a binary mode that supports file reading. Default value is 'rb'. * **valid_modes**: Tuple of valid modes for open files. This must include **mode**. If nothing is specified, **valid_mode** is set to **mode**. * **filename** - Name associated with open copy of PNG image. Default is 'texture.png'. """ class_info = 'a PNG image file' file_modes = {'rb', 'rb+', 'wb+', 'ab+'} def __init__(self, doc, mode='rb', **kwargs): kwargs.update( {'valid_modes': kwargs.get('valid_modes', ImagePNG.file_modes)} ) super(ImagePNG, self).__init__(doc, mode, **kwargs) @property def filename(self): """Bytestream image filename""" return getattr(self, '_filename', 'texture.png') @filename.setter def filename(self, value): if not isinstance(value, string_types): raise TypeError('Filename must be a string') self._filename = value def validate(self, instance, value): """Checks if value is an open PNG file, valid filename, or png.Image Returns an open bytestream of the image """ # Pass if already validated if getattr(value, '__valid__', False): return value # Validate that value is PNG if isinstance(value, png.Image): pass else: value = super(ImagePNG, self).validate(instance, value) try: png.Reader(value).validate_signature() except png.FormatError: self.error(instance, value, extra='Open file is not PNG.') # Write input to new bytestream output = BytesIO() = self.filename output.__valid__ = True if isinstance(value, png.Image): else: fid = value output.write( fid.close() return output @staticmethod def to_json(value, **kwargs): """Convert a PNG Image to base64-encoded JSON to_json assumes that value has passed validation. """ b64rep = base64.b64encode( jsonrep = '{preamble}{b64}'.format( preamble=PNG_PREAMBLE, b64=b64rep.decode(), ) return jsonrep @staticmethod def from_json(value, **kwargs): """Convert a PNG Image from base64-encoded JSON""" if not value.startswith(PNG_PREAMBLE): raise ValueError('Not a valid base64-encoded PNG image') infile = BytesIO() rep = base64.b64decode(value[len(PNG_PREAMBLE):].encode('utf-8')) infile.write(rep) return infile