发布于 2015-09-11 16:09:08 | 223 次阅读 | 评论: 0 | 来源: 网络整理
#
# The Python Imaging Library.
# $Id$
#
# base class for image file handlers
#
# history:
# 1995-09-09 fl Created
# 1996-03-11 fl Fixed load mechanism.
# 1996-04-15 fl Added pcx/xbm decoders.
# 1996-04-30 fl Added encoders.
# 1996-12-14 fl Added load helpers
# 1997-01-11 fl Use encode_to_file where possible
# 1997-08-27 fl Flush output in _save
# 1998-03-05 fl Use memory mapping for some modes
# 1999-02-04 fl Use memory mapping also for "I;16" and "I;16B"
# 1999-05-31 fl Added image parser
# 2000-10-12 fl Set readonly flag on memory-mapped images
# 2002-03-20 fl Use better messages for common decoder errors
# 2003-04-21 fl Fall back on mmap/map_buffer if map is not available
# 2003-10-30 fl Added StubImageFile class
# 2004-02-25 fl Made incremental parser more robust
#
# Copyright (c) 1997-2004 by Secret Labs AB
# Copyright (c) 1995-2004 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#
from PIL import Image
from PIL._util import isPath
import traceback, os, sys
import io
MAXBLOCK = 65536
SAFEBLOCK = 1024*1024
LOAD_TRUNCATED_IMAGES = False
ERRORS = {
-1: "image buffer overrun error",
-2: "decoding error",
-3: "unknown error",
-8: "bad configuration",
-9: "out of memory error"
}
def raise_ioerror(error):
try:
message = Image.core.getcodecstatus(error)
except AttributeError:
message = ERRORS.get(error)
if not message:
message = "decoder error %d" % error
raise IOError(message + " when reading image file")
#
# --------------------------------------------------------------------
# Helpers
def _tilesort(t):
# sort on offset
return t[2]
#
# --------------------------------------------------------------------
# ImageFile base class
class ImageFile(Image.Image):
"Base class for image file format handlers."
def __init__(self, fp=None, filename=None):
Image.Image.__init__(self)
self.tile = None
self.readonly = 1 # until we know better
self.decoderconfig = ()
self.decodermaxblock = MAXBLOCK
if isPath(fp):
# filename
self.fp = open(fp, "rb")
self.filename = fp
else:
# stream
self.fp = fp
self.filename = filename
try:
self._open()
except IndexError as v: # end of data
if Image.DEBUG > 1:
traceback.print_exc()
raise SyntaxError(v)
except TypeError as v: # end of data (ord)
if Image.DEBUG > 1:
traceback.print_exc()
raise SyntaxError(v)
except KeyError as v: # unsupported mode
if Image.DEBUG > 1:
traceback.print_exc()
raise SyntaxError(v)
except EOFError as v: # got header but not the first frame
if Image.DEBUG > 1:
traceback.print_exc()
raise SyntaxError(v)
if not self.mode or self.size[0] <= 0:
raise SyntaxError("not identified by this driver")
def draft(self, mode, size):
"Set draft mode"
pass
def verify(self):
"Check file integrity"
# raise exception if something's wrong. must be called
# directly after open, and closes file when finished.
self.fp = None
def load(self):
"Load image data based on tile list"
pixel = Image.Image.load(self)
if self.tile is None:
raise IOError("cannot load this image")
if not self.tile:
return pixel
self.map = None
readonly = 0
if self.filename and len(self.tile) == 1 and not hasattr(sys, 'pypy_version_info'):
# As of pypy 2.1.0, memory mapping was failing here.
# try memory mapping
d, e, o, a = self.tile[0]
if d == "raw" and a[0] == self.mode and a[0] in Image._MAPMODES:
try:
if hasattr(Image.core, "map"):
# use built-in mapper
self.map = Image.core.map(self.filename)
self.map.seek(o)
self.im = self.map.readimage(
self.mode, self.size, a[1], a[2]
)
else:
# use mmap, if possible
import mmap
file = open(self.filename, "r+")
size = os.path.getsize(self.filename)
# FIXME: on Unix, use PROT_READ etc
self.map = mmap.mmap(file.fileno(), size)
self.im = Image.core.map_buffer(
self.map, self.size, d, e, o, a
)
readonly = 1
except (AttributeError, EnvironmentError, ImportError):
self.map = None
self.load_prepare()
# look for read/seek overrides
try:
read = self.load_read
except AttributeError:
read = self.fp.read
try:
seek = self.load_seek
except AttributeError:
seek = self.fp.seek
if not self.map:
# sort tiles in file order
self.tile.sort(key=_tilesort)
try:
# FIXME: This is a hack to handle TIFF's JpegTables tag.
prefix = self.tile_prefix
except AttributeError:
prefix = b""
for d, e, o, a in self.tile:
d = Image._getdecoder(self.mode, d, a, self.decoderconfig)
seek(o)
try:
d.setimage(self.im, e)
except ValueError:
continue
b = prefix
t = len(b)
while True:
try:
s = read(self.decodermaxblock)
except IndexError as ie: # truncated png/gif
if LOAD_TRUNCATED_IMAGES:
break
else:
raise IndexError(ie)
if not s and not d.handles_eof: # truncated jpeg
self.tile = []
# JpegDecode needs to clean things up here either way
# If we don't destroy the decompressor, we have a memory leak.
d.cleanup()
if LOAD_TRUNCATED_IMAGES:
break
else:
raise IOError("image file is truncated (%d bytes not processed)" % len(b))
b = b + s
n, e = d.decode(b)
if n < 0:
break
b = b[n:]
t = t + n
self.tile = []
self.readonly = readonly
self.fp = None # might be shared
if not self.map and (not LOAD_TRUNCATED_IMAGES or t == 0) and e < 0:
# still raised if decoder fails to return anything
raise_ioerror(e)
# post processing
if hasattr(self, "tile_post_rotate"):
# FIXME: This is a hack to handle rotated PCD's
self.im = self.im.rotate(self.tile_post_rotate)
self.size = self.im.size
self.load_end()
return Image.Image.load(self)
def load_prepare(self):
# create image memory if necessary
if not self.im or
self.im.mode != self.mode or self.im.size != self.size:
self.im = Image.core.new(self.mode, self.size)
# create palette (optional)
if self.mode == "P":
Image.Image.load(self)
def load_end(self):
# may be overridden
pass
# may be defined for contained formats
# def load_seek(self, pos):
# pass
# may be defined for blocked formats (e.g. PNG)
# def load_read(self, bytes):
# pass
class StubImageFile(ImageFile):
"""
Base class for stub image loaders.
A stub loader is an image loader that can identify files of a
certain format, but relies on external code to load the file.
"""
def _open(self):
raise NotImplementedError(
"StubImageFile subclass must implement _open"
)
def load(self):
loader = self._load()
if loader is None:
raise IOError("cannot find loader for this %s file" % self.format)
image = loader.load(self)
assert image is not None
# become the other object (!)
self.__class__ = image.__class__
self.__dict__ = image.__dict__
def _load(self):
"(Hook) Find actual image loader."
raise NotImplementedError(
"StubImageFile subclass must implement _load"
)
[docs]class Parser:
"""
Incremental image parser. This class implements the standard
feed/close consumer interface.
In Python 2.x, this is an old-style class.
"""
incremental = None
image = None
data = None
decoder = None
finished = 0
[docs] def reset(self):
"""
(Consumer) Reset the parser. Note that you can only call this
method immediately after you've created a parser; parser
instances cannot be reused.
"""
assert self.data is None, "cannot reuse parsers"
[docs] def feed(self, data):
"""
(Consumer) Feed data to the parser.
:param data: A string buffer.
:exception IOError: If the parser failed to parse the image file.
"""
# collect data
if self.finished:
return
if self.data is None:
self.data = data
else:
self.data = self.data + data
# parse what we have
if self.decoder:
if self.offset > 0:
# skip header
skip = min(len(self.data), self.offset)
self.data = self.data[skip:]
self.offset = self.offset - skip
if self.offset > 0 or not self.data:
return
n, e = self.decoder.decode(self.data)
if n < 0:
# end of stream
self.data = None
self.finished = 1
if e < 0:
# decoding error
self.image = None
raise_ioerror(e)
else:
# end of image
return
self.data = self.data[n:]
elif self.image:
# if we end up here with no decoder, this file cannot
# be incrementally parsed. wait until we've gotten all
# available data
pass
else:
# attempt to open this file
try:
try:
fp = io.BytesIO(self.data)
im = Image.open(fp)
finally:
fp.close() # explicitly close the virtual file
except IOError:
# traceback.print_exc()
pass # not enough data
else:
flag = hasattr(im, "load_seek") or hasattr(im, "load_read")
if flag or len(im.tile) != 1:
# custom load code, or multiple tiles
self.decode = None
else:
# initialize decoder
im.load_prepare()
d, e, o, a = im.tile[0]
im.tile = []
self.decoder = Image._getdecoder(
im.mode, d, a, im.decoderconfig
)
self.decoder.setimage(im.im, e)
# calculate decoder offset
self.offset = o
if self.offset <= len(self.data):
self.data = self.data[self.offset:]
self.offset = 0
self.image = im
[docs] def close(self):
"""
(Consumer) Close the stream.
:returns: An image object.
:exception IOError: If the parser failed to parse the image file either
because it cannot be identified or cannot be
decoded.
"""
# finish decoding
if self.decoder:
# get rid of what's left in the buffers
self.feed(b"")
self.data = self.decoder = None
if not self.finished:
raise IOError("image was incomplete")
if not self.image:
raise IOError("cannot parse this image")
if self.data:
# incremental parsing not possible; reopen the file
# not that we have all data
try:
fp = io.BytesIO(self.data)
self.image = Image.open(fp)
finally:
self.image.load()
fp.close() # explicitly close the virtual file
return self.image
# --------------------------------------------------------------------
def _save(im, fp, tile, bufsize=0):
"""Helper to save image based on tile list
:param im: Image object.
:param fp: File object.
:param tile: Tile list.
:param bufsize: Optional buffer size
"""
im.load()
if not hasattr(im, "encoderconfig"):
im.encoderconfig = ()
tile.sort(key=_tilesort)
# FIXME: make MAXBLOCK a configuration parameter
# It would be great if we could have the encoder specifiy what it needs
# But, it would need at least the image size in most cases. RawEncode is
# a tricky case.
bufsize = max(MAXBLOCK, bufsize, im.size[0] * 4) # see RawEncode.c
try:
fh = fp.fileno()
fp.flush()
except (AttributeError, io.UnsupportedOperation):
# compress to Python file-compatible object
for e, b, o, a in tile:
e = Image._getencoder(im.mode, e, a, im.encoderconfig)
if o > 0:
fp.seek(o, 0)
e.setimage(im.im, b)
while True:
l, s, d = e.encode(bufsize)
fp.write(d)
if s:
break
if s < 0:
raise IOError("encoder error %d when writing image file" % s)
else:
# slight speedup: compress to real file object
for e, b, o, a in tile:
e = Image._getencoder(im.mode, e, a, im.encoderconfig)
if o > 0:
fp.seek(o, 0)
e.setimage(im.im, b)
s = e.encode_to_file(fh, bufsize)
if s < 0:
raise IOError("encoder error %d when writing image file" % s)
try:
fp.flush()
except: pass
def _safe_read(fp, size):
"""
Reads large blocks in a safe way. Unlike fp.read(n), this function
doesn't trust the user. If the requested size is larger than
SAFEBLOCK, the file is read block by block.
:param fp: File handle. Must implement a <b>read</b> method.
:param size: Number of bytes to read.
:returns: A string containing up to <i>size</i> bytes of data.
"""
if size <= 0:
return b""
if size <= SAFEBLOCK:
return fp.read(size)
data = []
while size > 0:
block = fp.read(min(size, SAFEBLOCK))
if not block:
break
data.append(block)
size = size - len(block)
return b"".join(data)