621 lines
17 KiB
Python
621 lines
17 KiB
Python
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#
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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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__version__ = "0.9"
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import re, string
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import Image, ImageFile, ImagePalette, zlib
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def i16(c):
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return ord(c[1]) + (ord(c[0])<<8)
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def i32(c):
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return ord(c[3]) + (ord(c[2])<<8) + (ord(c[1])<<16) + (ord(c[0])<<24)
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is_cid = re.compile("\w\w\w\w").match
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_MAGIC = "\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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# --------------------------------------------------------------------
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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, len = 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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len = 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, len
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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, len):
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self.queue.append((cid, pos, len))
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def call(self, cid, pos, len):
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"Call the appropriate chunk handler"
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if Image.DEBUG:
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print "STREAM", cid, pos, len
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return getattr(self, "chunk_" + cid)(pos, len)
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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 = "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 1:
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cid, pos, len = 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, len))
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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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if zip:
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import zlib
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self.add("zTXt", key + "\0\0" + zlib.compress(value))
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else:
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self.add("tEXt", key + "\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, len):
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# ICC profile
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s = ImageFile._safe_read(self.fp, len)
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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 = string.find(s, chr(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", ord(s[i])
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comp_method = ord(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, len):
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# image header
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s = ImageFile._safe_read(self.fp, len)
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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[(ord(s[8]), ord(s[9]))]
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except:
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pass
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if ord(s[12]):
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self.im_info["interlace"] = 1
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if ord(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, len):
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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 = len
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raise EOFError
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def chunk_IEND(self, pos, len):
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# end of PNG image
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raise EOFError
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def chunk_PLTE(self, pos, len):
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# palette
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s = ImageFile._safe_read(self.fp, len)
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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, len):
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# transparency
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s = ImageFile._safe_read(self.fp, len)
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if self.im_mode == "P":
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i = string.find(s, chr(0))
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if i >= 0:
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self.im_info["transparency"] = i
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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, len):
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# gamma setting
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s = ImageFile._safe_read(self.fp, len)
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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, len):
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# pixels per unit
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s = ImageFile._safe_read(self.fp, len)
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px, py = i32(s), i32(s[4:])
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unit = ord(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, len):
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# text
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s = ImageFile._safe_read(self.fp, len)
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try:
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k, v = string.split(s, "\0", 1)
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except ValueError:
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k = s; v = "" # fallback for broken tEXt tags
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if k:
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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, len):
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# compressed text
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s = ImageFile._safe_read(self.fp, len)
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k, v = string.split(s, "\0", 1)
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comp_method = ord(v[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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self.im_info[k] = self.im_text[k] = zlib.decompress(v[1:])
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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 1:
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#
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# get next chunk
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cid, pos, len = self.png.read()
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try:
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s = self.png.call(cid, pos, len)
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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, len, "(unknown)"
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s = ImageFile._safe_read(self.fp, len)
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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 = len # 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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||
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"internal: prepare to read PNG file"
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||
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||
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if self.info.get("interlace"):
|
||
|
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self.decoderconfig = self.decoderconfig + (1,)
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||
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ImageFile.ImageFile.load_prepare(self)
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def load_read(self, bytes):
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"internal: read more image data"
|
||
|
|
|
||
|
|
while self.__idat == 0:
|
||
|
|
# end of chunk, skip forward to next one
|
||
|
|
|
||
|
|
self.fp.read(4) # CRC
|
||
|
|
|
||
|
|
cid, pos, len = self.png.read()
|
||
|
|
|
||
|
|
if cid not in ["IDAT", "DDAT"]:
|
||
|
|
self.png.push(cid, pos, len)
|
||
|
|
return ""
|
||
|
|
|
||
|
|
self.__idat = len # empty chunks are allowed
|
||
|
|
|
||
|
|
# read more data from this chunk
|
||
|
|
if bytes <= 0:
|
||
|
|
bytes = self.__idat
|
||
|
|
else:
|
||
|
|
bytes = min(bytes, self.__idat)
|
||
|
|
|
||
|
|
self.__idat = self.__idat - bytes
|
||
|
|
|
||
|
|
return self.fp.read(bytes)
|
||
|
|
|
||
|
|
|
||
|
|
def load_end(self):
|
||
|
|
"internal: finished reading image data"
|
||
|
|
|
||
|
|
self.png.close()
|
||
|
|
self.png = None
|
||
|
|
|
||
|
|
|
||
|
|
# --------------------------------------------------------------------
|
||
|
|
# PNG writer
|
||
|
|
|
||
|
|
def o16(i):
|
||
|
|
return chr(i>>8&255) + chr(i&255)
|
||
|
|
|
||
|
|
def o32(i):
|
||
|
|
return chr(i>>24&255) + chr(i>>16&255) + chr(i>>8&255) + chr(i&255)
|
||
|
|
|
||
|
|
_OUTMODES = {
|
||
|
|
# supported PIL modes, and corresponding rawmodes/bits/color combinations
|
||
|
|
"1": ("1", chr(1)+chr(0)),
|
||
|
|
"L;1": ("L;1", chr(1)+chr(0)),
|
||
|
|
"L;2": ("L;2", chr(2)+chr(0)),
|
||
|
|
"L;4": ("L;4", chr(4)+chr(0)),
|
||
|
|
"L": ("L", chr(8)+chr(0)),
|
||
|
|
"LA": ("LA", chr(8)+chr(4)),
|
||
|
|
"I": ("I;16B", chr(16)+chr(0)),
|
||
|
|
"P;1": ("P;1", chr(1)+chr(3)),
|
||
|
|
"P;2": ("P;2", chr(2)+chr(3)),
|
||
|
|
"P;4": ("P;4", chr(4)+chr(3)),
|
||
|
|
"P": ("P", chr(8)+chr(3)),
|
||
|
|
"RGB": ("RGB", chr(8)+chr(2)),
|
||
|
|
"RGBA":("RGBA", chr(8)+chr(6)),
|
||
|
|
}
|
||
|
|
|
||
|
|
def putchunk(fp, cid, *data):
|
||
|
|
"Write a PNG chunk (including CRC field)"
|
||
|
|
|
||
|
|
data = string.join(data, "")
|
||
|
|
|
||
|
|
fp.write(o32(len(data)) + cid)
|
||
|
|
fp.write(data)
|
||
|
|
hi, lo = Image.core.crc32(data, Image.core.crc32(cid))
|
||
|
|
fp.write(o16(hi) + o16(lo))
|
||
|
|
|
||
|
|
class _idat:
|
||
|
|
# wrap output from the encoder in IDAT chunks
|
||
|
|
|
||
|
|
def __init__(self, fp, chunk):
|
||
|
|
self.fp = fp
|
||
|
|
self.chunk = chunk
|
||
|
|
def write(self, data):
|
||
|
|
self.chunk(self.fp, "IDAT", data)
|
||
|
|
|
||
|
|
def _save(im, fp, filename, chunk=putchunk, check=0):
|
||
|
|
# save an image to disk (called by the save method)
|
||
|
|
|
||
|
|
mode = im.mode
|
||
|
|
|
||
|
|
if mode == "P":
|
||
|
|
|
||
|
|
#
|
||
|
|
# attempt to minimize storage requirements for palette images
|
||
|
|
|
||
|
|
if im.encoderinfo.has_key("bits"):
|
||
|
|
|
||
|
|
# number of bits specified by user
|
||
|
|
n = 1 << im.encoderinfo["bits"]
|
||
|
|
|
||
|
|
else:
|
||
|
|
|
||
|
|
# check palette contents
|
||
|
|
n = 256 # FIXME
|
||
|
|
|
||
|
|
if n <= 2:
|
||
|
|
bits = 1
|
||
|
|
elif n <= 4:
|
||
|
|
bits = 2
|
||
|
|
elif n <= 16:
|
||
|
|
bits = 4
|
||
|
|
else:
|
||
|
|
bits = 8
|
||
|
|
|
||
|
|
if bits != 8:
|
||
|
|
mode = "%s;%d" % (mode, bits)
|
||
|
|
|
||
|
|
# encoder options
|
||
|
|
if im.encoderinfo.has_key("dictionary"):
|
||
|
|
dictionary = im.encoderinfo["dictionary"]
|
||
|
|
else:
|
||
|
|
dictionary = ""
|
||
|
|
|
||
|
|
im.encoderconfig = (im.encoderinfo.has_key("optimize"), dictionary)
|
||
|
|
|
||
|
|
# get the corresponding PNG mode
|
||
|
|
try:
|
||
|
|
rawmode, mode = _OUTMODES[mode]
|
||
|
|
except KeyError:
|
||
|
|
raise IOError, "cannot write mode %s as PNG" % mode
|
||
|
|
|
||
|
|
if check:
|
||
|
|
return check
|
||
|
|
|
||
|
|
#
|
||
|
|
# write minimal PNG file
|
||
|
|
|
||
|
|
fp.write(_MAGIC)
|
||
|
|
|
||
|
|
chunk(fp, "IHDR",
|
||
|
|
o32(im.size[0]), o32(im.size[1]), # 0: size
|
||
|
|
mode, # 8: depth/type
|
||
|
|
chr(0), # 10: compression
|
||
|
|
chr(0), # 11: filter category
|
||
|
|
chr(0)) # 12: interlace flag
|
||
|
|
|
||
|
|
if im.mode == "P":
|
||
|
|
chunk(fp, "PLTE", im.im.getpalette("RGB"))
|
||
|
|
|
||
|
|
if im.encoderinfo.has_key("transparency"):
|
||
|
|
if im.mode == "P":
|
||
|
|
transparency = max(0, min(255, im.encoderinfo["transparency"]))
|
||
|
|
chunk(fp, "tRNS", chr(255) * transparency + chr(0))
|
||
|
|
elif im.mode == "L":
|
||
|
|
transparency = max(0, min(65535, im.encoderinfo["transparency"]))
|
||
|
|
chunk(fp, "tRNS", o16(transparency))
|
||
|
|
elif im.mode == "RGB":
|
||
|
|
red, green, blue = im.encoderinfo["transparency"]
|
||
|
|
chunk(fp, "tRNS", o16(red) + o16(green) + o16(blue))
|
||
|
|
else:
|
||
|
|
raise IOError("cannot use transparency for this mode")
|
||
|
|
|
||
|
|
if 0:
|
||
|
|
# FIXME: to be supported some day
|
||
|
|
chunk(fp, "gAMA", o32(int(gamma * 100000.0)))
|
||
|
|
|
||
|
|
dpi = im.encoderinfo.get("dpi")
|
||
|
|
if dpi:
|
||
|
|
chunk(fp, "pHYs",
|
||
|
|
o32(int(dpi[0] / 0.0254 + 0.5)),
|
||
|
|
o32(int(dpi[1] / 0.0254 + 0.5)),
|
||
|
|
chr(1))
|
||
|
|
|
||
|
|
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.has_key("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)
|
||
|
|
try:
|
||
|
|
import ICCProfile
|
||
|
|
p = ICCProfile.ICCProfile(im.info["icc_profile"])
|
||
|
|
name = p.tags.desc.get("ASCII", p.tags.desc.get("Unicode", p.tags.desc.get("Macintosh", p.tags.desc.get("en", {}).get("US", "ICC Profile")))).encode("latin1", "replace")[:79]
|
||
|
|
except ImportError:
|
||
|
|
name = "ICC Profile"
|
||
|
|
data = name + "\0\0" + zlib.compress(im.info["icc_profile"])
|
||
|
|
chunk(fp, "iCCP", data)
|
||
|
|
|
||
|
|
ImageFile._save(im, _idat(fp, chunk), [("zip", (0,0)+im.size, 0, rawmode)])
|
||
|
|
|
||
|
|
chunk(fp, "IEND", "")
|
||
|
|
|
||
|
|
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 = string.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")
|