Source code for PIL.ImageFile

#
# 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.
#

import io
import struct
import sys
import warnings

from . import Image
from ._util import isPath

MAXBLOCK = 65536

SAFEBLOCK = 1024 * 1024

LOAD_TRUNCATED_IMAGES = False
"""Whether or not to load truncated image files. User code may change this."""

ERRORS = {
    -1: "image buffer overrun error",
    -2: "decoding error",
    -3: "unknown error",
    -8: "bad configuration",
    -9: "out of memory error",
}
"""Dict of known error codes returned from :meth:`.PyDecoder.decode`."""


#
# --------------------------------------------------------------------
# Helpers


def raise_oserror(error):
    try:
        message = Image.core.getcodecstatus(error)
    except AttributeError:
        message = ERRORS.get(error)
    if not message:
        message = f"decoder error {error}"
    raise OSError(message + " when reading image file")


def raise_ioerror(error):
    warnings.warn(
        "raise_ioerror is deprecated and will be removed in a future release. "
        "Use raise_oserror instead.",
        DeprecationWarning,
    )
    return raise_oserror(error)


def _tilesort(t):
    # sort on offset
    return t[2]


#
# --------------------------------------------------------------------
# ImageFile base class


[docs]class ImageFile(Image.Image): """Base class for image file format handlers.""" def __init__(self, fp=None, filename=None): super().__init__() self._min_frame = 0 self.custom_mimetype = None self.tile = None """ A list of tile descriptors, or ``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 self._exclusive_fp = True else: # stream self.fp = fp self.filename = filename # can be overridden self._exclusive_fp = None try: try: self._open() except ( IndexError, # end of data TypeError, # end of data (ord) KeyError, # unsupported mode EOFError, # got header but not the first frame struct.error, ) as v: raise SyntaxError(v) from v if not self.mode or self.size[0] <= 0: raise SyntaxError("not identified by this driver") except BaseException: # close the file only if we have opened it this constructor if self._exclusive_fp: self.fp.close() raise
[docs] def get_format_mimetype(self): if self.custom_mimetype: return self.custom_mimetype if self.format is not None: return Image.MIME.get(self.format.upper())
[docs] def verify(self): """Check file integrity""" # raise exception if something's wrong. must be called # directly after open, and closes file when finished. if self._exclusive_fp: self.fp.close() self.fp = None
[docs] def load(self): """Load image data based on tile list""" if self.tile is None: raise OSError("cannot load this image") pixel = Image.Image.load(self) if not self.tile: return pixel self.map = None use_mmap = self.filename and len(self.tile) == 1 # As of pypy 2.1.0, memory mapping was failing here. use_mmap = use_mmap and not hasattr(sys, "pypy_version_info") readonly = 0 # look for read/seek overrides try: read = self.load_read # don't use mmap if there are custom read/seek functions use_mmap = False except AttributeError: read = self.fp.read try: seek = self.load_seek use_mmap = False except AttributeError: seek = self.fp.seek if use_mmap: # try memory mapping decoder_name, extents, offset, args = self.tile[0] if ( decoder_name == "raw" and len(args) >= 3 and args[0] == self.mode and args[0] in Image._MAPMODES ): try: if hasattr(Image.core, "map"): # use built-in mapper WIN32 only self.map = Image.core.map(self.filename) self.map.seek(offset) self.im = self.map.readimage( self.mode, self.size, args[1], args[2] ) else: # use mmap, if possible import mmap with open(self.filename) as fp: self.map = mmap.mmap( fp.fileno(), 0, access=mmap.ACCESS_READ ) self.im = Image.core.map_buffer( self.map, self.size, decoder_name, offset, args ) readonly = 1 # After trashing self.im, # we might need to reload the palette data. if self.palette: self.palette.dirty = 1 except (AttributeError, OSError, ImportError): self.map = None self.load_prepare() err_code = -3 # initialize to unknown error 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 decoder_name, extents, offset, args in self.tile: decoder = Image._getdecoder( self.mode, decoder_name, args, self.decoderconfig ) try: seek(offset) decoder.setimage(self.im, extents) if decoder.pulls_fd: decoder.setfd(self.fp) status, err_code = decoder.decode(b"") else: b = prefix while True: try: s = read(self.decodermaxblock) except (IndexError, struct.error) as e: # truncated png/gif if LOAD_TRUNCATED_IMAGES: break else: raise OSError("image file is truncated") from e if not s: # truncated jpeg if LOAD_TRUNCATED_IMAGES: break else: raise OSError( "image file is truncated " f"({len(b)} bytes not processed)" ) b = b + s n, err_code = decoder.decode(b) if n < 0: break b = b[n:] finally: # Need to cleanup here to prevent leaks decoder.cleanup() self.tile = [] self.readonly = readonly self.load_end() if self._exclusive_fp and self._close_exclusive_fp_after_loading: self.fp.close() self.fp = None if not self.map and not LOAD_TRUNCATED_IMAGES and err_code < 0: # still raised if decoder fails to return anything raise_oserror(err_code) return Image.Image.load(self)
[docs] 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)
[docs] 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 def _seek_check(self, frame): if ( frame < self._min_frame # Only check upper limit on frames if additional seek operations # are not required to do so or ( not (hasattr(self, "_n_frames") and self._n_frames is None) and frame >= self.n_frames + self._min_frame ) ): raise EOFError("attempt to seek outside sequence") return self.tell() != frame
[docs]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")
[docs] def load(self): loader = self._load() if loader is None: raise OSError(f"cannot find loader for this {self.format} file") 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. """ incremental = None image = None data = None decoder = None offset = 0 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 OSError: 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_oserror(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: with io.BytesIO(self.data) as fp: im = Image.open(fp) except OSError: # 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
def __enter__(self): return self def __exit__(self, *args): self.close()
[docs] def close(self): """ (Consumer) Close the stream. :returns: An image object. :exception OSError: 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 OSError("image was incomplete") if not self.image: raise OSError("cannot parse this image") if self.data: # incremental parsing not possible; reopen the file # not that we have all data with io.BytesIO(self.data) as fp: try: self.image = Image.open(fp) finally: self.image.load() 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 specify 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 if fp == sys.stdout: fp.flush() return try: fh = fp.fileno() fp.flush() except (AttributeError, io.UnsupportedOperation) as exc: # 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) e.setimage(im.im, b) if e.pushes_fd: e.setfd(fp) l, s = e.encode_to_pyfd() else: while True: l, s, d = e.encode(bufsize) fp.write(d) if s: break if s < 0: raise OSError(f"encoder error {s} when writing image file") from exc e.cleanup() 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) e.setimage(im.im, b) if e.pushes_fd: e.setfd(fp) l, s = e.encode_to_pyfd() else: s = e.encode_to_file(fh, bufsize) if s < 0: raise OSError(f"encoder error {s} when writing image file") e.cleanup() if hasattr(fp, "flush"): fp.flush() 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 -= len(block) return b"".join(data) class PyCodecState: def __init__(self): self.xsize = 0 self.ysize = 0 self.xoff = 0 self.yoff = 0 def extents(self): return (self.xoff, self.yoff, self.xoff + self.xsize, self.yoff + self.ysize)
[docs]class PyDecoder: """ Python implementation of a format decoder. Override this class and add the decoding logic in the :meth:`decode` method. See :ref:`Writing Your Own File Decoder in Python<file-decoders-py>` """ _pulls_fd = False def __init__(self, mode, *args): self.im = None self.state = PyCodecState() self.fd = None self.mode = mode self.init(args)
[docs] def init(self, args): """ Override to perform decoder specific initialization :param args: Array of args items from the tile entry :returns: None """ self.args = args
@property def pulls_fd(self): return self._pulls_fd
[docs] def decode(self, buffer): """ Override to perform the decoding process. :param buffer: A bytes object with the data to be decoded. :returns: A tuple of ``(bytes consumed, errcode)``. If finished with decoding return <0 for the bytes consumed. Err codes are from :data:`.ImageFile.ERRORS`. """ raise NotImplementedError()
[docs] def cleanup(self): """ Override to perform decoder specific cleanup :returns: None """ pass
[docs] def setfd(self, fd): """ Called from ImageFile to set the python file-like object :param fd: A python file-like object :returns: None """ self.fd = fd
[docs] def setimage(self, im, extents=None): """ Called from ImageFile to set the core output image for the decoder :param im: A core image object :param extents: a 4 tuple of (x0, y0, x1, y1) defining the rectangle for this tile :returns: None """ # following c code self.im = im if extents: (x0, y0, x1, y1) = extents else: (x0, y0, x1, y1) = (0, 0, 0, 0) if x0 == 0 and x1 == 0: self.state.xsize, self.state.ysize = self.im.size else: self.state.xoff = x0 self.state.yoff = y0 self.state.xsize = x1 - x0 self.state.ysize = y1 - y0 if self.state.xsize <= 0 or self.state.ysize <= 0: raise ValueError("Size cannot be negative") if ( self.state.xsize + self.state.xoff > self.im.size[0] or self.state.ysize + self.state.yoff > self.im.size[1] ): raise ValueError("Tile cannot extend outside image")
[docs] def set_as_raw(self, data, rawmode=None): """ Convenience method to set the internal image from a stream of raw data :param data: Bytes to be set :param rawmode: The rawmode to be used for the decoder. If not specified, it will default to the mode of the image :returns: None """ if not rawmode: rawmode = self.mode d = Image._getdecoder(self.mode, "raw", (rawmode)) d.setimage(self.im, self.state.extents()) s = d.decode(data) if s[0] >= 0: raise ValueError("not enough image data") if s[1] != 0: raise ValueError("cannot decode image data")