117 lines
3.5 KiB
Python
117 lines
3.5 KiB
Python
# -*- coding: UTF-8 -*-
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#/**
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# * Software Name : pycrate
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# * Version : 0.4
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# *
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# * Copyright 2016. Benoit Michau. ANSSI.
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# *
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# * This library is free software; you can redistribute it and/or
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# * modify it under the terms of the GNU Lesser General Public
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# * License as published by the Free Software Foundation; either
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# * version 2.1 of the License, or (at your option) any later version.
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# *
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# * This library is distributed in the hope that it will be useful,
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# * but WITHOUT ANY WARRANTY; without even the implied warranty of
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# * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# * Lesser General Public License for more details.
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# *
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# * You should have received a copy of the GNU Lesser General Public
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# * License along with this library; if not, write to the Free Software
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# * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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# * MA 02110-1301 USA
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# *
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# *--------------------------------------------------------
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# * File Name : pycrate_media/PNG.py
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# * Created : 2016-03-08
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# * Authors : Benoit Michau
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# *--------------------------------------------------------
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#*/
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from zlib import crc32
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from pycrate_core.elt import *
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from pycrate_core.base import *
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from pycrate_core.repr import *
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Buf.REPR_MAXLEN = 256
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_Colour_dict = {
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0 : 'Greyscale',
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2 : 'Truecolour',
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3 : 'Indexed-colour',
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4 : 'Greyscale with alpha',
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6 : 'Truecolour with alpha'
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}
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_CompMeth_dict = {
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0 : 'inflate/deflate with sliding window'
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}
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_FilterMeth_dict = {
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0 : 'adaptative filtering with 5 basic filter types',
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}
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_InterMeth_dict = {
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0 : 'no interlace',
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1 : 'Adam7 interlace'
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}
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class IHDR(Envelope):
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_GEN = (
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Uint32('width'),
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Uint32('height'),
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Uint8('depth', desc='bit depth'),
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Uint8('color', desc='color type', dic=_Colour_dict),
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Uint8('comp', desc='compression method', dic=_CompMeth_dict),
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Uint8('filter', desc='filter method', dic=_FilterMeth_dict),
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Uint8('interlace', desc='interlace method', dic=_InterMeth_dict)
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)
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class PaletteEntry(Envelope):
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_GEN = (
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Uint8('Red'),
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Uint8('Green'),
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Uint8('Blue')
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)
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class PLTE(Array):
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_GEN = PaletteEntry()
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class PNGChunk(Envelope):
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CHK_CRC = True
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_GEN = (
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Uint32('len'),
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Buf('type', bl=32),
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Buf('data', rep=REPR_HD),
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Uint32('crc', rep=REPR_HEX)
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)
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def __init__(self, *args, **kwargs):
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Envelope.__init__(self, *args, **kwargs)
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self[0].set_valauto(self[2].get_len)
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self[2].set_blauto(lambda: 8*self[0].get_val())
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self[3].set_valauto(lambda: crc32(self[1:3].to_bytes()) & 0xffffffff)
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def _from_char(self, char):
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Envelope._from_char(self, char)
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chunk_len, chunk_type = self[0].get_val(), self[1].get_val()
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if chunk_type == b'IHDR' and chunk_len == 13:
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ihdr = IHDR()
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ihdr.from_bytes(self[2].to_bytes())
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self.replace(self[2], ihdr)
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elif chunk_type == b'PLTE' and chunk_len % 3 == 0:
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plte = PLTE()
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plte.set_num(chunk_len//3)
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plte.from_bytes(self[2].to_bytes())
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self.replace(self[2], plte)
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#
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if self.CHK_CRC:
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crc = self[3].get_val()
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self[3].reautomate()
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if self[3].get_val() != crc:
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log('warning, bad CRC32 for chunk {0}'.format(self[1].get_val()))
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class PNG(Envelope):
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_GEN = (
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Buf('sig', desc='PNG signature', val=b'\x89PNG\r\n\x1a\n', bl=64),
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Sequence('PNGBody', hier=1, GEN=PNGChunk())
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)
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