Source code for pytomo.kaa_metadata.image.png
# -*- coding: iso-8859-1 -*-
# -----------------------------------------------------------------------------
# png.py - png file parsing
# -----------------------------------------------------------------------------
# $Id: png.py 3079 2008-02-13 20:10:40Z dmeyer $
#
# -----------------------------------------------------------------------------
# kaa-Metadata - Media Metadata for Python
# Copyright (C) 2003-2006 Thomas Schueppel, Dirk Meyer
#
# First Edition: Thomas Schueppel <stain@acm.org>
# Maintainer: Dirk Meyer <dischi@freevo.org>
#
# Please see the file AUTHORS for a complete list of authors.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MER-
# CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# -----------------------------------------------------------------------------
from __future__ import absolute_import
__all__ = ['Parser']
# python imports
import struct
import zlib
import logging
# kaa imports
#import kaa
# use strutils instead of kaa
from .. import strutils as kaa
# import kaa_metadata.image core
from . import core
# get logging object
log = logging.getLogger('metadata')
# interesting file format info:
# http://www.libpng.org/pub/png/png-sitemap.html#programming
# http://pmt.sourceforge.net/pngmeta/
# http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
PNGSIGNATURE = "\211PNG\r\n\032\n"
class PNG(core.Image):
def __init__(self,file):
core.Image.__init__(self)
self.mime = 'image/png'
self.type = 'PNG image'
signature = file.read(8)
if ( signature != PNGSIGNATURE ):
raise core.ParseError()
self.meta = {}
while self._readChunk(file):
pass
if len(self.meta.keys()):
self._appendtable( 'PNGMETA', self.meta )
for key, value in self.meta.items():
if key.startswith('Thumb:') or key == 'Software':
self._set(key, value)
def _readChunk(self,file):
try:
(length, type) = struct.unpack('>I4s', file.read(8))
except (OSError, IOError, struct.error):
return 0
key = None
if type == 'IEND':
return 0
elif type == 'IHDR':
data = file.read(length+4)
self.width, self.height, self.depth = struct.unpack(">IIb", data[:9])
elif type == 'tEXt':
log.debug('latin-1 Text found.')
(data, crc) = struct.unpack('>%isI' % length,file.read(length+4))
(key, value) = data.split('\0')
self.meta[key] = kaa.str_to_unicode(value)
elif type == 'zTXt':
log.debug('Compressed Text found.')
(data,crc) = struct.unpack('>%isI' % length,file.read(length+4))
split = data.split('\0')
key = split[0]
value = "".join(split[1:])
compression = ord(value[0])
value = value[1:]
if compression == 0:
decompressed = zlib.decompress(value)
log.debug("%s (Compressed %i) -> %s" % \
(key,compression,decompressed))
else:
log.debug("%s has unknown Compression %c" % (key,compression))
self.meta[key] = kaa.str_to_unicode(value)
elif type == 'iTXt':
log.debug('International Text found.')
(data,crc) = struct.unpack('>%isI' % length,file.read(length+4))
(key, value) = data.split('\0')
self.meta[key] = kaa.str_to_unicode(value)
else:
file.seek(length+4,1)
log.debug("%s of length %d ignored." % (type, length))
if key is not None and key.lower() == "comment":
self.comment = self.meta[key]
return 1
Parser = PNG