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.
#

from . import Image
from ._util import isPath
import io
import sys
import struct

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._min_frame = 0

        self.custom_mimetype = None

        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
            self._exclusive_fp = True
        else:
            # stream
            self.fp = fp
            self.filename = filename
            # can be overridden
            self._exclusive_fp = None

        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:
            # close the file only if we have opened it this constructor
            if self._exclusive_fp:
                self.fp.close()
            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 get_format_mimetype(self):
        if self.format is None:
            return
        return self.custom_mimetype or Image.MIME.get(self.format.upper())

    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

    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
        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, "r") 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, extents,
                            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, EnvironmentError, 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):
                                # truncated png/gif
                                if LOAD_TRUNCATED_IMAGES:
                                    break
                                else:
                                    raise IOError("image file is truncated")

                            if not s:  # truncated jpeg
                                if LOAD_TRUNCATED_IMAGES:
                                    break
                                else:
                                    self.tile = []
                                    raise IOError("image file is truncated "
                                                  "(%d bytes not processed)" %
                                                  len(b))

                            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_ioerror(err_code)

        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

    def _seek_check(self, frame):
        if (frame < self._min_frame or
            # Only check upper limit on frames if additional seek operations
            # are not required to do so
            (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


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(object): """ 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 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: with io.BytesIO(self.data) as fp: im = Image.open(fp) 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
def __enter__(self): return self def __exit__(self, *args): self.close()
[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 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): # 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) 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 IOError("encoder error %d when writing image file" % s) 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, 0) 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 IOError("encoder error %d when writing image file" % s) 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(object): 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(object): """ Python implementation of a format decoder. Override this class and add the decoding logic in the `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. If `handles_eof` is set, then `buffer` will be empty and `self.fd` will be set. :returns: A tuple of (bytes consumed, errcode). If finished with decoding return <0 for the bytes consumed. Err codes are from `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")