File size: 24,421 Bytes
b72ab63
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
#
# 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 __future__ import annotations

import io
import itertools
import struct
import sys
from typing import IO, Any, NamedTuple

from . import Image
from ._deprecate import deprecate
from ._util import is_path

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`,
:meth:`.PyEncoder.encode` :meth:`.PyEncoder.encode_to_pyfd` and
:meth:`.PyEncoder.encode_to_file`.
"""


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


def _get_oserror(error, *, encoder):
    try:
        msg = Image.core.getcodecstatus(error)
    except AttributeError:
        msg = ERRORS.get(error)
    if not msg:
        msg = f"{'encoder' if encoder else 'decoder'} error {error}"
    msg += f" when {'writing' if encoder else 'reading'} image file"
    return OSError(msg)


def raise_oserror(error):
    deprecate(
        "raise_oserror",
        12,
        action="It is only useful for translating error codes returned by a codec's "
        "decode() method, which ImageFile already does automatically.",
    )
    raise _get_oserror(error, encoder=False)


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


class _Tile(NamedTuple):
    codec_name: str
    extents: tuple[int, int, int, int]
    offset: int
    args: tuple[Any, ...] | str | None


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


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 is_path(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 or self.size[1] <= 0:
                msg = "not identified by this driver"
                raise SyntaxError(msg)
        except BaseException:
            # close the file only if we have opened it this constructor
            if self._exclusive_fp:
                self.fp.close()
            raise

    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())

    def __setstate__(self, state):
        self.tile = []
        super().__setstate__(state)

    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"""

        if self.tile is None:
            msg = "cannot load this image"
            raise OSError(msg)

        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 isinstance(args, str):
                args = (args, 0, 1)
            if (
                decoder_name == "raw"
                and len(args) >= 3
                and args[0] == self.mode
                and args[0] in Image._MAPMODES
            ):
                try:
                    # use mmap, if possible
                    import mmap

                    with open(self.filename) as fp:
                        self.map = mmap.mmap(fp.fileno(), 0, access=mmap.ACCESS_READ)
                    if offset + self.size[1] * args[1] > self.map.size():
                        msg = "buffer is not large enough"
                        raise OSError(msg)
                    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""

            # Remove consecutive duplicates that only differ by their offset
            self.tile = [
                list(tiles)[-1]
                for _, tiles in itertools.groupby(
                    self.tile, lambda tile: (tile[0], tile[1], tile[3])
                )
            ]
            for decoder_name, extents, offset, args in self.tile:
                seek(offset)
                decoder = Image._getdecoder(
                    self.mode, decoder_name, args, self.decoderconfig
                )
                try:
                    decoder.setimage(self.im, extents)
                    if decoder.pulls_fd:
                        decoder.setfd(self.fp)
                        err_code = decoder.decode(b"")[1]
                    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:
                                    msg = "image file is truncated"
                                    raise OSError(msg) from e

                            if not s:  # truncated jpeg
                                if LOAD_TRUNCATED_IMAGES:
                                    break
                                else:
                                    msg = (
                                        "image file is truncated "
                                        f"({len(b)} bytes not processed)"
                                    )
                                    raise OSError(msg)

                            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 _get_oserror(err_code, encoder=False)

        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, read_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
            )
        ):
            msg = "attempt to seek outside sequence"
            raise EOFError(msg)

        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):
        msg = "StubImageFile subclass must implement _open"
        raise NotImplementedError(msg)

    def load(self):
        loader = self._load()
        if loader is None:
            msg = f"cannot find loader for this {self.format} file"
            raise OSError(msg)
        image = loader.load(self)
        assert image is not None
        # become the other object (!)
        self.__class__ = image.__class__
        self.__dict__ = image.__dict__
        return image.load()

    def _load(self):
        """(Hook) Find actual image loader."""
        msg = "StubImageFile subclass must implement _load"
        raise NotImplementedError(msg)


class Parser:
    """
    Incremental image parser.  This class implements the standard
    feed/close consumer interface.
    """

    incremental = None
    image: Image.Image | None = None
    data = None
    decoder = None
    offset = 0
    finished = 0

    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"

    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 _get_oserror(e, encoder=False)
                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:
                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()

    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:
                msg = "image was incomplete"
                raise OSError(msg)
        if not self.image:
            msg = "cannot parse this image"
            raise OSError(msg)
        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) -> None:
    """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
    try:
        fh = fp.fileno()
        fp.flush()
        _encode_tile(im, fp, tile, bufsize, fh)
    except (AttributeError, io.UnsupportedOperation) as exc:
        _encode_tile(im, fp, tile, bufsize, None, exc)
    if hasattr(fp, "flush"):
        fp.flush()


def _encode_tile(im, fp, tile: list[_Tile], bufsize, fh, exc=None):
    for encoder_name, extents, offset, args in tile:
        if offset > 0:
            fp.seek(offset)
        encoder = Image._getencoder(im.mode, encoder_name, args, im.encoderconfig)
        try:
            encoder.setimage(im.im, extents)
            if encoder.pushes_fd:
                encoder.setfd(fp)
                errcode = encoder.encode_to_pyfd()[1]
            else:
                if exc:
                    # compress to Python file-compatible object
                    while True:
                        errcode, data = encoder.encode(bufsize)[1:]
                        fp.write(data)
                        if errcode:
                            break
                else:
                    # slight speedup: compress to real file object
                    errcode = encoder.encode_to_file(fh, bufsize)
            if errcode < 0:
                raise _get_oserror(errcode, encoder=True) from exc
        finally:
            encoder.cleanup()


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 <i>size</i> bytes of data.

    Raises an OSError if the file is truncated and the read cannot be completed

    """
    if size <= 0:
        return b""
    if size <= SAFEBLOCK:
        data = fp.read(size)
        if len(data) < size:
            msg = "Truncated File Read"
            raise OSError(msg)
        return data
    data = []
    remaining_size = size
    while remaining_size > 0:
        block = fp.read(min(remaining_size, SAFEBLOCK))
        if not block:
            break
        data.append(block)
        remaining_size -= len(block)
    if sum(len(d) for d in data) < size:
        msg = "Truncated File Read"
        raise OSError(msg)
    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


class PyCodec:
    fd: IO[bytes] | None

    def __init__(self, mode, *args):
        self.im = None
        self.state = PyCodecState()
        self.fd = None
        self.mode = mode
        self.init(args)

    def init(self, args):
        """
        Override to perform codec specific initialization

        :param args: Array of args items from the tile entry
        :returns: None
        """
        self.args = args

    def cleanup(self):
        """
        Override to perform codec specific cleanup

        :returns: None
        """
        pass

    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

    def setimage(self, im, extents=None):
        """
        Called from ImageFile to set the core output image for the codec

        :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:
            msg = "Size cannot be negative"
            raise ValueError(msg)

        if (
            self.state.xsize + self.state.xoff > self.im.size[0]
            or self.state.ysize + self.state.yoff > self.im.size[1]
        ):
            msg = "Tile cannot extend outside image"
            raise ValueError(msg)


class PyDecoder(PyCodec):
    """
    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 Codec in Python<file-codecs-py>`
    """

    _pulls_fd = False

    @property
    def pulls_fd(self):
        return self._pulls_fd

    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 -1 for the bytes consumed.
            Err codes are from :data:`.ImageFile.ERRORS`.
        """
        msg = "unavailable in base decoder"
        raise NotImplementedError(msg)

    def set_as_raw(self, data: bytes, rawmode=None) -> 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:
            msg = "not enough image data"
            raise ValueError(msg)
        if s[1] != 0:
            msg = "cannot decode image data"
            raise ValueError(msg)


class PyEncoder(PyCodec):
    """
    Python implementation of a format encoder. Override this class and
    add the decoding logic in the :meth:`encode` method.

    See :ref:`Writing Your Own File Codec in Python<file-codecs-py>`
    """

    _pushes_fd = False

    @property
    def pushes_fd(self):
        return self._pushes_fd

    def encode(self, bufsize):
        """
        Override to perform the encoding process.

        :param bufsize: Buffer size.
        :returns: A tuple of ``(bytes encoded, errcode, bytes)``.
            If finished with encoding return 1 for the error code.
            Err codes are from :data:`.ImageFile.ERRORS`.
        """
        msg = "unavailable in base encoder"
        raise NotImplementedError(msg)

    def encode_to_pyfd(self):
        """
        If ``pushes_fd`` is ``True``, then this method will be used,
        and ``encode()`` will only be called once.

        :returns: A tuple of ``(bytes consumed, errcode)``.
            Err codes are from :data:`.ImageFile.ERRORS`.
        """
        if not self.pushes_fd:
            return 0, -8  # bad configuration
        bytes_consumed, errcode, data = self.encode(0)
        if data:
            self.fd.write(data)
        return bytes_consumed, errcode

    def encode_to_file(self, fh, bufsize):
        """
        :param fh: File handle.
        :param bufsize: Buffer size.

        :returns: If finished successfully, return 0.
            Otherwise, return an error code. Err codes are from
            :data:`.ImageFile.ERRORS`.
        """
        errcode = 0
        while errcode == 0:
            status, errcode, buf = self.encode(bufsize)
            if status > 0:
                fh.write(buf[status:])
        return errcode