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-rw-r--r--PIL/PngImagePlugin.py558
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diff --git a/PIL/PngImagePlugin.py b/PIL/PngImagePlugin.py
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+#
+# The Python Imaging Library.
+# $Id: PngImagePlugin.py 2203 2004-12-19 14:32:32Z fredrik $
+#
+# PNG support code
+#
+# See "PNG (Portable Network Graphics) Specification, version 1.0;
+# W3C Recommendation", 1996-10-01, Thomas Boutell (ed.).
+#
+# history:
+# 1996-05-06 fl Created (couldn't resist it)
+# 1996-12-14 fl Upgraded, added read and verify support (0.2)
+# 1996-12-15 fl Separate PNG stream parser
+# 1996-12-29 fl Added write support, added getchunks
+# 1996-12-30 fl Eliminated circular references in decoder (0.3)
+# 1998-07-12 fl Read/write 16-bit images as mode I (0.4)
+# 2001-02-08 fl Added transparency support (from Zircon) (0.5)
+# 2001-04-16 fl Don't close data source in "open" method (0.6)
+# 2004-02-24 fl Don't even pretend to support interlaced files (0.7)
+# 2004-08-31 fl Do basic sanity check on chunk identifiers (0.8)
+# 2004-09-20 fl Added PngInfo chunk container
+# 2004-12-18 fl Added DPI read support (based on code by Niki Spahiev)
+#
+# Copyright (c) 1997-2004 by Secret Labs AB
+# Copyright (c) 1996 by Fredrik Lundh
+#
+# See the README file for information on usage and redistribution.
+#
+
+__version__ = "0.8.2"
+
+import re, string
+
+import Image, ImageFile, ImagePalette
+
+
+def i16(c):
+ return ord(c[1]) + (ord(c[0])<<8)
+def i32(c):
+ return ord(c[3]) + (ord(c[2])<<8) + (ord(c[1])<<16) + (ord(c[0])<<24)
+
+is_cid = re.compile("\w\w\w\w").match
+
+
+_MAGIC = "\211PNG\r\n\032\n"
+
+
+_MODES = {
+ # supported bits/color combinations, and corresponding modes/rawmodes
+ (1, 0): ("1", "1"),
+ (2, 0): ("L", "L;2"),
+ (4, 0): ("L", "L;4"),
+ (8, 0): ("L", "L"),
+ (16,0): ("I", "I;16B"),
+ (8, 2): ("RGB", "RGB"),
+ (16,2): ("RGB", "RGB;16B"),
+ (1, 3): ("P", "P;1"),
+ (2, 3): ("P", "P;2"),
+ (4, 3): ("P", "P;4"),
+ (8, 3): ("P", "P"),
+ (8, 4): ("LA", "LA"),
+ (16,4): ("RGBA", "LA;16B"), # LA;16B->LA not yet available
+ (8, 6): ("RGBA", "RGBA"),
+ (16,6): ("RGBA", "RGBA;16B"),
+}
+
+
+# --------------------------------------------------------------------
+# Support classes. Suitable for PNG and related formats like MNG etc.
+
+class ChunkStream:
+
+ def __init__(self, fp):
+
+ self.fp = fp
+ self.queue = []
+
+ if not hasattr(Image.core, "crc32"):
+ self.crc = self.crc_skip
+
+ def read(self):
+ "Fetch a new chunk. Returns header information."
+
+ if self.queue:
+ cid, pos, len = self.queue[-1]
+ del self.queue[-1]
+ self.fp.seek(pos)
+ else:
+ s = self.fp.read(8)
+ cid = s[4:]
+ pos = self.fp.tell()
+ len = i32(s)
+
+ if not is_cid(cid):
+ raise SyntaxError, "broken PNG file (chunk %s)" % repr(cid)
+
+ return cid, pos, len
+
+ def close(self):
+ self.queue = self.crc = self.fp = None
+
+ def push(self, cid, pos, len):
+
+ self.queue.append((cid, pos, len))
+
+ def call(self, cid, pos, len):
+ "Call the appropriate chunk handler"
+
+ if Image.DEBUG:
+ print "STREAM", cid, pos, len
+ return getattr(self, "chunk_" + cid)(pos, len)
+
+ def crc(self, cid, data):
+ "Read and verify checksum"
+
+ crc1 = Image.core.crc32(data, Image.core.crc32(cid))
+ crc2 = i16(self.fp.read(2)), i16(self.fp.read(2))
+ if crc1 != crc2:
+ raise SyntaxError, "broken PNG file"\
+ "(bad header checksum in %s)" % cid
+
+ def crc_skip(self, cid, data):
+ "Read checksum. Used if the C module is not present"
+
+ self.fp.read(4)
+
+ def verify(self, endchunk = "IEND"):
+
+ # Simple approach; just calculate checksum for all remaining
+ # blocks. Must be called directly after open.
+
+ cids = []
+
+ while 1:
+ cid, pos, len = self.read()
+ if cid == endchunk:
+ break
+ self.crc(cid, ImageFile._safe_read(self.fp, len))
+ cids.append(cid)
+
+ return cids
+
+
+# --------------------------------------------------------------------
+# PNG chunk container (for use with save(pnginfo=))
+
+class PngInfo:
+
+ def __init__(self):
+ self.chunks = []
+
+ def add(self, cid, data):
+ self.chunks.append((cid, data))
+
+ def add_text(self, key, value, zip=0):
+ if zip:
+ import zlib
+ self.add("zTXt", key + "\0\0" + zlib.compress(value))
+ else:
+ self.add("tEXt", key + "\0" + value)
+
+# --------------------------------------------------------------------
+# PNG image stream (IHDR/IEND)
+
+class PngStream(ChunkStream):
+
+ def __init__(self, fp):
+
+ ChunkStream.__init__(self, fp)
+
+ # local copies of Image attributes
+ self.im_info = {}
+ self.im_size = (0,0)
+ self.im_mode = None
+ self.im_tile = None
+ self.im_palette = None
+
+ def chunk_IHDR(self, pos, len):
+
+ # image header
+ s = ImageFile._safe_read(self.fp, len)
+ self.im_size = i32(s), i32(s[4:])
+ try:
+ self.im_mode, self.im_rawmode = _MODES[(ord(s[8]), ord(s[9]))]
+ except:
+ pass
+ if ord(s[12]):
+ self.im_info["interlace"] = 1
+ if ord(s[11]):
+ raise SyntaxError, "unknown filter category"
+ return s
+
+ def chunk_IDAT(self, pos, len):
+
+ # image data
+ self.im_tile = [("zip", (0,0)+self.im_size, pos, self.im_rawmode)]
+ self.im_idat = len
+ raise EOFError
+
+ def chunk_IEND(self, pos, len):
+
+ # end of PNG image
+ raise EOFError
+
+ def chunk_PLTE(self, pos, len):
+
+ # palette
+ s = ImageFile._safe_read(self.fp, len)
+ if self.im_mode == "P":
+ self.im_palette = "RGB", s
+ return s
+
+ def chunk_tRNS(self, pos, len):
+
+ # transparency
+ s = ImageFile._safe_read(self.fp, len)
+ if self.im_mode == "P":
+ i = string.find(s, chr(0))
+ if i >= 0:
+ self.im_info["transparency"] = i
+ elif self.im_mode == "L":
+ self.im_info["transparency"] = i16(s)
+ return s
+
+ def chunk_gAMA(self, pos, len):
+
+ # gamma setting
+ s = ImageFile._safe_read(self.fp, len)
+ self.im_info["gamma"] = i32(s) / 100000.0
+ return s
+
+ def chunk_pHYs(self, pos, len):
+
+ # pixels per unit
+ s = ImageFile._safe_read(self.fp, len)
+ px, py = i32(s), i32(s[4:])
+ unit = ord(s[8])
+ if unit == 1: # meter
+ dpi = int(px * 0.0254 + 0.5), int(py * 0.0254 + 0.5)
+ self.im_info["dpi"] = dpi
+ elif unit == 0:
+ self.im_info["aspect"] = px, py
+ return s
+
+ def chunk_tEXt(self, pos, len):
+
+ # text
+ s = ImageFile._safe_read(self.fp, len)
+ try:
+ k, v = string.split(s, "\0", 1)
+ except ValueError:
+ k = s; v = "" # fallback for broken tEXt tags
+ if k:
+ self.im_info[k] = v
+ return s
+
+
+# --------------------------------------------------------------------
+# PNG reader
+
+def _accept(prefix):
+ return prefix[:8] == _MAGIC
+
+##
+# Image plugin for PNG images.
+
+class PngImageFile(ImageFile.ImageFile):
+
+ format = "PNG"
+ format_description = "Portable network graphics"
+
+ def _open(self):
+
+ if self.fp.read(8) != _MAGIC:
+ raise SyntaxError, "not a PNG file"
+
+ #
+ # Parse headers up to the first IDAT chunk
+
+ self.png = PngStream(self.fp)
+
+ while 1:
+
+ #
+ # get next chunk
+
+ cid, pos, len = self.png.read()
+
+ try:
+ s = self.png.call(cid, pos, len)
+ except EOFError:
+ break
+ except AttributeError:
+ if Image.DEBUG:
+ print cid, pos, len, "(unknown)"
+ s = ImageFile._safe_read(self.fp, len)
+
+ self.png.crc(cid, s)
+
+ #
+ # Copy relevant attributes from the PngStream. An alternative
+ # would be to let the PngStream class modify these attributes
+ # directly, but that introduces circular references which are
+ # difficult to break if things go wrong in the decoder...
+ # (believe me, I've tried ;-)
+
+ self.mode = self.png.im_mode
+ self.size = self.png.im_size
+ self.info = self.png.im_info
+ self.tile = self.png.im_tile
+
+ if self.png.im_palette:
+ rawmode, data = self.png.im_palette
+ self.palette = ImagePalette.raw(rawmode, data)
+
+ self.__idat = len # used by load_read()
+
+
+ def verify(self):
+ "Verify PNG file"
+
+ if self.fp is None:
+ raise RuntimeError("verify must be called directly after open")
+
+ # back up to beginning of IDAT block
+ self.fp.seek(self.tile[0][2] - 8)
+
+ self.png.verify()
+ self.png.close()
+
+ self.fp = None
+
+ def load_prepare(self):
+ "internal: prepare to read PNG file"
+
+ if self.info.get("interlace"):
+ raise IOError("cannot read interlaced PNG files")
+
+ ImageFile.ImageFile.load_prepare(self)
+
+ def load_read(self, bytes):
+ "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))
+ 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)
+
+ 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")
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