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668 lines
19 KiB
Python
668 lines
19 KiB
Python
#
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# The Python Imaging Library.
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# $Id$
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#
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# PNG support code
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#
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# See "PNG (Portable Network Graphics) Specification, version 1.0;
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# W3C Recommendation", 1996-10-01, Thomas Boutell (ed.).
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#
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# history:
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# 1996-05-06 fl Created (couldn't resist it)
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# 1996-12-14 fl Upgraded, added read and verify support (0.2)
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# 1996-12-15 fl Separate PNG stream parser
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# 1996-12-29 fl Added write support, added getchunks
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# 1996-12-30 fl Eliminated circular references in decoder (0.3)
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# 1998-07-12 fl Read/write 16-bit images as mode I (0.4)
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# 2001-02-08 fl Added transparency support (from Zircon) (0.5)
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# 2001-04-16 fl Don't close data source in "open" method (0.6)
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# 2004-02-24 fl Don't even pretend to support interlaced files (0.7)
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# 2004-08-31 fl Do basic sanity check on chunk identifiers (0.8)
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# 2004-09-20 fl Added PngInfo chunk container
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# 2004-12-18 fl Added DPI read support (based on code by Niki Spahiev)
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# 2008-08-13 fl Added tRNS support for RGB images
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# 2009-03-06 fl Support for preserving ICC profiles (by Florian Hoech)
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# 2009-03-08 fl Added zTXT support (from Lowell Alleman)
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# 2009-03-29 fl Read interlaced PNG files (from Conrado Porto Lopes Gouvua)
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#
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# Copyright (c) 1997-2009 by Secret Labs AB
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# Copyright (c) 1996 by Fredrik Lundh
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#
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# See the README file for information on usage and redistribution.
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#
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from __future__ import print_function
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__version__ = "0.9"
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import re
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from PIL import Image, ImageFile, ImagePalette, _binary
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import zlib
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i8 = _binary.i8
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i16 = _binary.i16be
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i32 = _binary.i32be
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is_cid = re.compile(b"\w\w\w\w").match
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_MAGIC = b"\211PNG\r\n\032\n"
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_MODES = {
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# supported bits/color combinations, and corresponding modes/rawmodes
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(1, 0): ("1", "1"),
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(2, 0): ("L", "L;2"),
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(4, 0): ("L", "L;4"),
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(8, 0): ("L", "L"),
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(16,0): ("I", "I;16B"),
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(8, 2): ("RGB", "RGB"),
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(16,2): ("RGB", "RGB;16B"),
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(1, 3): ("P", "P;1"),
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(2, 3): ("P", "P;2"),
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(4, 3): ("P", "P;4"),
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(8, 3): ("P", "P"),
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(8, 4): ("LA", "LA"),
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(16,4): ("RGBA", "LA;16B"), # LA;16B->LA not yet available
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(8, 6): ("RGBA", "RGBA"),
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(16,6): ("RGBA", "RGBA;16B"),
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}
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_simple_palette = re.compile(b'^\xff+\x00\xff*$')
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# --------------------------------------------------------------------
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# Support classes. Suitable for PNG and related formats like MNG etc.
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class ChunkStream:
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def __init__(self, fp):
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self.fp = fp
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self.queue = []
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if not hasattr(Image.core, "crc32"):
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self.crc = self.crc_skip
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def read(self):
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"Fetch a new chunk. Returns header information."
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if self.queue:
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cid, pos, length = self.queue[-1]
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del self.queue[-1]
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self.fp.seek(pos)
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else:
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s = self.fp.read(8)
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cid = s[4:]
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pos = self.fp.tell()
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length = i32(s)
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if not is_cid(cid):
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raise SyntaxError("broken PNG file (chunk %s)" % repr(cid))
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return cid, pos, length
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def close(self):
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self.queue = self.crc = self.fp = None
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def push(self, cid, pos, length):
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self.queue.append((cid, pos, length))
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def call(self, cid, pos, length):
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"Call the appropriate chunk handler"
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if Image.DEBUG:
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print("STREAM", cid, pos, length)
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return getattr(self, "chunk_" + cid.decode('ascii'))(pos, length)
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def crc(self, cid, data):
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"Read and verify checksum"
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crc1 = Image.core.crc32(data, Image.core.crc32(cid))
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crc2 = i16(self.fp.read(2)), i16(self.fp.read(2))
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if crc1 != crc2:
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raise SyntaxError("broken PNG file"\
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"(bad header checksum in %s)" % cid)
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def crc_skip(self, cid, data):
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"Read checksum. Used if the C module is not present"
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self.fp.read(4)
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def verify(self, endchunk = b"IEND"):
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# Simple approach; just calculate checksum for all remaining
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# blocks. Must be called directly after open.
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cids = []
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while True:
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cid, pos, length = self.read()
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if cid == endchunk:
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break
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self.crc(cid, ImageFile._safe_read(self.fp, length))
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cids.append(cid)
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return cids
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# --------------------------------------------------------------------
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# PNG chunk container (for use with save(pnginfo=))
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class PngInfo:
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def __init__(self):
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self.chunks = []
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def add(self, cid, data):
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self.chunks.append((cid, data))
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def add_text(self, key, value, zip=0):
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# The tEXt chunk stores latin-1 text
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if not isinstance(key, bytes):
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key = key.encode('latin-1', 'strict')
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if not isinstance(value, bytes):
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value = value.encode('latin-1', 'replace')
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if zip:
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import zlib
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self.add(b"zTXt", key + b"\0\0" + zlib.compress(value))
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else:
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self.add(b"tEXt", key + b"\0" + value)
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# --------------------------------------------------------------------
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# PNG image stream (IHDR/IEND)
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class PngStream(ChunkStream):
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def __init__(self, fp):
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ChunkStream.__init__(self, fp)
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# local copies of Image attributes
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self.im_info = {}
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self.im_text = {}
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self.im_size = (0,0)
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self.im_mode = None
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self.im_tile = None
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self.im_palette = None
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def chunk_iCCP(self, pos, length):
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# ICC profile
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s = ImageFile._safe_read(self.fp, length)
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# according to PNG spec, the iCCP chunk contains:
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# Profile name 1-79 bytes (character string)
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# Null separator 1 byte (null character)
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# Compression method 1 byte (0)
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# Compressed profile n bytes (zlib with deflate compression)
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i = s.find(b"\0")
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if Image.DEBUG:
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print("iCCP profile name", s[:i])
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print("Compression method", i8(s[i]))
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comp_method = i8(s[i])
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if comp_method != 0:
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raise SyntaxError("Unknown compression method %s in iCCP chunk" % comp_method)
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try:
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icc_profile = zlib.decompress(s[i+2:])
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except zlib.error:
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icc_profile = None # FIXME
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self.im_info["icc_profile"] = icc_profile
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return s
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def chunk_IHDR(self, pos, length):
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# image header
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s = ImageFile._safe_read(self.fp, length)
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self.im_size = i32(s), i32(s[4:])
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try:
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self.im_mode, self.im_rawmode = _MODES[(i8(s[8]), i8(s[9]))]
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except:
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pass
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if i8(s[12]):
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self.im_info["interlace"] = 1
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if i8(s[11]):
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raise SyntaxError("unknown filter category")
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return s
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def chunk_IDAT(self, pos, length):
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# image data
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self.im_tile = [("zip", (0,0)+self.im_size, pos, self.im_rawmode)]
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self.im_idat = length
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raise EOFError
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def chunk_IEND(self, pos, length):
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# end of PNG image
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raise EOFError
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def chunk_PLTE(self, pos, length):
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# palette
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s = ImageFile._safe_read(self.fp, length)
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if self.im_mode == "P":
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self.im_palette = "RGB", s
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return s
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def chunk_tRNS(self, pos, length):
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# transparency
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s = ImageFile._safe_read(self.fp, length)
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if self.im_mode == "P":
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if _simple_palette.match(s):
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i = s.find(b"\0")
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if i >= 0:
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self.im_info["transparency"] = i
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else:
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self.im_info["transparency"] = s
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elif self.im_mode == "L":
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self.im_info["transparency"] = i16(s)
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elif self.im_mode == "RGB":
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self.im_info["transparency"] = i16(s), i16(s[2:]), i16(s[4:])
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return s
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def chunk_gAMA(self, pos, length):
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# gamma setting
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s = ImageFile._safe_read(self.fp, length)
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self.im_info["gamma"] = i32(s) / 100000.0
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return s
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def chunk_pHYs(self, pos, length):
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# pixels per unit
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s = ImageFile._safe_read(self.fp, length)
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px, py = i32(s), i32(s[4:])
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unit = i8(s[8])
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if unit == 1: # meter
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dpi = int(px * 0.0254 + 0.5), int(py * 0.0254 + 0.5)
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self.im_info["dpi"] = dpi
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elif unit == 0:
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self.im_info["aspect"] = px, py
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return s
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def chunk_tEXt(self, pos, length):
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# text
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s = ImageFile._safe_read(self.fp, length)
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try:
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k, v = s.split(b"\0", 1)
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except ValueError:
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k = s; v = b"" # fallback for broken tEXt tags
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if k:
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if bytes is not str:
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k = k.decode('latin-1', 'strict')
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v = v.decode('latin-1', 'replace')
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self.im_info[k] = self.im_text[k] = v
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return s
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def chunk_zTXt(self, pos, length):
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# compressed text
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s = ImageFile._safe_read(self.fp, length)
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try:
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k, v = s.split(b"\0", 1)
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except ValueError:
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k = s; v = b""
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if v:
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comp_method = i8(v[0])
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else:
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comp_method = 0
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if comp_method != 0:
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raise SyntaxError("Unknown compression method %s in zTXt chunk" % comp_method)
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import zlib
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try:
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v = zlib.decompress(v[1:])
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except zlib.error:
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v = b""
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if k:
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if bytes is not str:
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k = k.decode('latin-1', 'strict')
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v = v.decode('latin-1', 'replace')
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self.im_info[k] = self.im_text[k] = v
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return s
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# --------------------------------------------------------------------
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# PNG reader
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def _accept(prefix):
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return prefix[:8] == _MAGIC
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##
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# Image plugin for PNG images.
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class PngImageFile(ImageFile.ImageFile):
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format = "PNG"
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format_description = "Portable network graphics"
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def _open(self):
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if self.fp.read(8) != _MAGIC:
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raise SyntaxError("not a PNG file")
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#
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# Parse headers up to the first IDAT chunk
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self.png = PngStream(self.fp)
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while True:
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#
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# get next chunk
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cid, pos, length = self.png.read()
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try:
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s = self.png.call(cid, pos, length)
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except EOFError:
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break
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except AttributeError:
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if Image.DEBUG:
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print(cid, pos, length, "(unknown)")
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s = ImageFile._safe_read(self.fp, length)
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self.png.crc(cid, s)
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#
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# Copy relevant attributes from the PngStream. An alternative
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# would be to let the PngStream class modify these attributes
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# directly, but that introduces circular references which are
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# difficult to break if things go wrong in the decoder...
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# (believe me, I've tried ;-)
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self.mode = self.png.im_mode
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self.size = self.png.im_size
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self.info = self.png.im_info
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self.text = self.png.im_text # experimental
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self.tile = self.png.im_tile
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if self.png.im_palette:
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rawmode, data = self.png.im_palette
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self.palette = ImagePalette.raw(rawmode, data)
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self.__idat = length # used by load_read()
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def verify(self):
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"Verify PNG file"
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if self.fp is None:
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raise RuntimeError("verify must be called directly after open")
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# back up to beginning of IDAT block
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self.fp.seek(self.tile[0][2] - 8)
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self.png.verify()
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self.png.close()
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self.fp = None
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def load_prepare(self):
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"internal: prepare to read PNG file"
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if self.info.get("interlace"):
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self.decoderconfig = self.decoderconfig + (1,)
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ImageFile.ImageFile.load_prepare(self)
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def load_read(self, read_bytes):
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"internal: read more image data"
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while self.__idat == 0:
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# end of chunk, skip forward to next one
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self.fp.read(4) # CRC
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cid, pos, length = self.png.read()
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if cid not in [b"IDAT", b"DDAT"]:
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self.png.push(cid, pos, length)
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return b""
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self.__idat = length # empty chunks are allowed
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# read more data from this chunk
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if read_bytes <= 0:
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read_bytes = self.__idat
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else:
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read_bytes = min(read_bytes, self.__idat)
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self.__idat = self.__idat - read_bytes
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return self.fp.read(read_bytes)
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def load_end(self):
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"internal: finished reading image data"
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self.png.close()
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self.png = None
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# --------------------------------------------------------------------
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# PNG writer
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o8 = _binary.o8
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o16 = _binary.o16be
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o32 = _binary.o32be
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_OUTMODES = {
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# supported PIL modes, and corresponding rawmodes/bits/color combinations
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"1": ("1", b'\x01\x00'),
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"L;1": ("L;1", b'\x01\x00'),
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"L;2": ("L;2", b'\x02\x00'),
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"L;4": ("L;4", b'\x04\x00'),
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"L": ("L", b'\x08\x00'),
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"LA": ("LA", b'\x08\x04'),
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"I": ("I;16B", b'\x10\x00'),
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"P;1": ("P;1", b'\x01\x03'),
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"P;2": ("P;2", b'\x02\x03'),
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"P;4": ("P;4", b'\x04\x03'),
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"P": ("P", b'\x08\x03'),
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"RGB": ("RGB", b'\x08\x02'),
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"RGBA":("RGBA", b'\x08\x06'),
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}
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def putchunk(fp, cid, *data):
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"Write a PNG chunk (including CRC field)"
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data = b"".join(data)
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fp.write(o32(len(data)) + cid)
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fp.write(data)
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hi, lo = Image.core.crc32(data, Image.core.crc32(cid))
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fp.write(o16(hi) + o16(lo))
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class _idat:
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# wrap output from the encoder in IDAT chunks
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def __init__(self, fp, chunk):
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self.fp = fp
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self.chunk = chunk
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def write(self, data):
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self.chunk(self.fp, b"IDAT", data)
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def _save(im, fp, filename, chunk=putchunk, check=0):
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# save an image to disk (called by the save method)
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mode = im.mode
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if mode == "P":
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#
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# attempt to minimize storage requirements for palette images
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if "bits" in im.encoderinfo:
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# number of bits specified by user
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colors = 1 << im.encoderinfo["bits"]
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else:
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# check palette contents
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if im.palette:
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colors = max(min(len(im.palette.getdata()[1])//3, 256), 2)
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else:
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colors = 256
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if colors <= 2:
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bits = 1
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elif colors <= 4:
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bits = 2
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elif colors <= 16:
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bits = 4
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else:
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bits = 8
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if bits != 8:
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mode = "%s;%d" % (mode, bits)
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# encoder options
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if "dictionary" in im.encoderinfo:
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dictionary = im.encoderinfo["dictionary"]
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else:
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dictionary = b""
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im.encoderconfig = ("optimize" in im.encoderinfo,
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im.encoderinfo.get("compress_level", -1),
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im.encoderinfo.get("compress_type", -1),
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dictionary)
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# get the corresponding PNG mode
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try:
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rawmode, mode = _OUTMODES[mode]
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except KeyError:
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raise IOError("cannot write mode %s as PNG" % mode)
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if check:
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return check
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#
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# write minimal PNG file
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fp.write(_MAGIC)
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chunk(fp, b"IHDR",
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o32(im.size[0]), o32(im.size[1]), # 0: size
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mode, # 8: depth/type
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b'\0', # 10: compression
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b'\0', # 11: filter category
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b'\0') # 12: interlace flag
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if im.mode == "P":
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palette_byte_number = (2 ** bits) * 3
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palette_bytes = im.im.getpalette("RGB")[:palette_byte_number]
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while len(palette_bytes) < palette_byte_number:
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palette_bytes += b'\0'
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chunk(fp, b"PLTE", palette_bytes)
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transparency = im.encoderinfo.get('transparency',im.info.get('transparency', None))
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if transparency or transparency == 0:
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if im.mode == "P":
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# limit to actual palette size
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alpha_bytes = 2**bits
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if isinstance(transparency, bytes):
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chunk(fp, b"tRNS", transparency[:alpha_bytes])
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else:
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transparency = max(0, min(255, transparency))
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alpha = b'\xFF' * transparency + b'\0'
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chunk(fp, b"tRNS", alpha[:alpha_bytes])
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elif im.mode == "L":
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transparency = max(0, min(65535, transparency))
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chunk(fp, b"tRNS", o16(transparency))
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elif im.mode == "RGB":
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red, green, blue = transparency
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chunk(fp, b"tRNS", o16(red) + o16(green) + o16(blue))
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else:
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if "transparency" in im.encoderinfo:
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# don't bother with transparency if it's an RGBA
|
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# and it's in the info dict. It's probably just stale.
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raise IOError("cannot use transparency for this mode")
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else:
|
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if im.mode == "P" and im.im.getpalettemode() == "RGBA":
|
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alpha = im.im.getpalette("RGBA", "A")
|
|
alpha_bytes = 2**bits
|
|
chunk(fp, b"tRNS", alpha[:alpha_bytes])
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|
|
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if 0:
|
|
# FIXME: to be supported some day
|
|
chunk(fp, b"gAMA", o32(int(gamma * 100000.0)))
|
|
|
|
dpi = im.encoderinfo.get("dpi")
|
|
if dpi:
|
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chunk(fp, b"pHYs",
|
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o32(int(dpi[0] / 0.0254 + 0.5)),
|
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o32(int(dpi[1] / 0.0254 + 0.5)),
|
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b'\x01')
|
|
|
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info = im.encoderinfo.get("pnginfo")
|
|
if info:
|
|
for cid, data in info.chunks:
|
|
chunk(fp, cid, data)
|
|
|
|
# ICC profile writing support -- 2008-06-06 Florian Hoech
|
|
if im.info.get("icc_profile"):
|
|
# ICC profile
|
|
# according to PNG spec, the iCCP chunk contains:
|
|
# Profile name 1-79 bytes (character string)
|
|
# Null separator 1 byte (null character)
|
|
# Compression method 1 byte (0)
|
|
# Compressed profile n bytes (zlib with deflate compression)
|
|
name = b"ICC Profile"
|
|
data = name + b"\0\0" + zlib.compress(im.info["icc_profile"])
|
|
chunk(fp, b"iCCP", data)
|
|
|
|
ImageFile._save(im, _idat(fp, chunk), [("zip", (0,0)+im.size, 0, rawmode)])
|
|
|
|
chunk(fp, b"IEND", b"")
|
|
|
|
try:
|
|
fp.flush()
|
|
except:
|
|
pass
|
|
|
|
|
|
# --------------------------------------------------------------------
|
|
# PNG chunk converter
|
|
|
|
def getchunks(im, **params):
|
|
"""Return a list of PNG chunks representing this image."""
|
|
|
|
class collector:
|
|
data = []
|
|
def write(self, data):
|
|
pass
|
|
def append(self, chunk):
|
|
self.data.append(chunk)
|
|
|
|
def append(fp, cid, *data):
|
|
data = b"".join(data)
|
|
hi, lo = Image.core.crc32(data, Image.core.crc32(cid))
|
|
crc = o16(hi) + o16(lo)
|
|
fp.append((cid, data, crc))
|
|
|
|
fp = collector()
|
|
|
|
try:
|
|
im.encoderinfo = params
|
|
_save(im, fp, None, append)
|
|
finally:
|
|
del im.encoderinfo
|
|
|
|
return fp.data
|
|
|
|
|
|
# --------------------------------------------------------------------
|
|
# Registry
|
|
|
|
Image.register_open("PNG", PngImageFile, _accept)
|
|
Image.register_save("PNG", _save)
|
|
|
|
Image.register_extension("PNG", ".png")
|
|
|
|
Image.register_mime("PNG", "image/png")
|