File: PngImagePlugin.py

package info (click to toggle)
pillow 2.6.1-2%2Bdeb8u3
  • links: PTS
  • area: main
  • in suites: jessie
  • size: 13,812 kB
  • ctags: 4,987
  • sloc: ansic: 23,760; python: 20,267; makefile: 375; sh: 74
file content (782 lines) | stat: -rw-r--r-- 22,669 bytes parent folder | download | duplicates (2)
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
#
# The Python Imaging Library.
# $Id$
#
# 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)
# 2008-08-13 fl   Added tRNS support for RGB images
# 2009-03-06 fl   Support for preserving ICC profiles (by Florian Hoech)
# 2009-03-08 fl   Added zTXT support (from Lowell Alleman)
# 2009-03-29 fl   Read interlaced PNG files (from Conrado Porto Lopes Gouvua)
#
# Copyright (c) 1997-2009 by Secret Labs AB
# Copyright (c) 1996 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#

from __future__ import print_function

__version__ = "0.9"

import re

from PIL import Image, ImageFile, ImagePalette, _binary
import zlib

i8 = _binary.i8
i16 = _binary.i16be
i32 = _binary.i32be

is_cid = re.compile(b"\w\w\w\w").match


_MAGIC = b"\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"),
}


_simple_palette = re.compile(b'^\xff+\x00\xff*$')

# Maximum decompressed size for a iTXt or zTXt chunk.
# Eliminates decompression bombs where compressed chunks can expand 1000x
MAX_TEXT_CHUNK = ImageFile.SAFEBLOCK
# Set the maximum total text chunk size.
MAX_TEXT_MEMORY = 64 * MAX_TEXT_CHUNK

def _safe_zlib_decompress(s):
    dobj = zlib.decompressobj()
    plaintext = dobj.decompress(s, MAX_TEXT_CHUNK)
    if dobj.unconsumed_tail:
        raise ValueError("Decompressed Data Too Large")
    return plaintext


# --------------------------------------------------------------------
# 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, length = self.queue[-1]
            del self.queue[-1]
            self.fp.seek(pos)
        else:
            s = self.fp.read(8)
            cid = s[4:]
            pos = self.fp.tell()
            length = i32(s)

        if not is_cid(cid):
            raise SyntaxError("broken PNG file (chunk %s)" % repr(cid))

        return cid, pos, length

    def close(self):
        self.queue = self.crc = self.fp = None

    def push(self, cid, pos, length):

        self.queue.append((cid, pos, length))

    def call(self, cid, pos, length):
        "Call the appropriate chunk handler"

        if Image.DEBUG:
            print("STREAM", cid, pos, length)
        return getattr(self, "chunk_" + cid.decode('ascii'))(pos, length)

    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=b"IEND"):

        # Simple approach; just calculate checksum for all remaining
        # blocks.  Must be called directly after open.

        cids = []

        while True:
            cid, pos, length = self.read()
            if cid == endchunk:
                break
            self.crc(cid, ImageFile._safe_read(self.fp, length))
            cids.append(cid)

        return cids


# --------------------------------------------------------------------
# Subclass of string to allow iTXt chunks to look like strings while
# keeping their extra information

class iTXt(str):
    @staticmethod
    def __new__(cls, text, lang, tkey):
        self = str.__new__(cls, text)
        self.lang = lang
        self.tkey = tkey
        return self


# --------------------------------------------------------------------
# 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_itxt(self, key, value, lang="", tkey="", zip=False):
        if not isinstance(key, bytes):
            key = key.encode("latin-1", "strict")
        if not isinstance(value, bytes):
            value = value.encode("utf-8", "strict")
        if not isinstance(lang, bytes):
            lang = lang.encode("utf-8", "strict")
        if not isinstance(tkey, bytes):
            tkey = tkey.encode("utf-8", "strict")

        if zip:
            import zlib
            self.add(b"iTXt", key + b"\0\x01\0" + lang + b"\0" + tkey + b"\0" +
                     zlib.compress(value))
        else:
            self.add(b"iTXt", key + b"\0\0\0" + lang + b"\0" + tkey + b"\0" +
                     value)

    def add_text(self, key, value, zip=0):
        if isinstance(value, iTXt):
            return self.add_itxt(key, value, value.lang, value.tkey, bool(zip))

        # The tEXt chunk stores latin-1 text
        if not isinstance(value, bytes):
            try:
                value = value.encode('latin-1', 'strict')
            except UnicodeError:
                return self.add_itxt(key, value, zip=bool(zip))

        if not isinstance(key, bytes):
            key = key.encode('latin-1', 'strict')

        if zip:
            import zlib
            self.add(b"zTXt", key + b"\0\0" + zlib.compress(value))
        else:
            self.add(b"tEXt", key + b"\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_text = {}
        self.im_size = (0, 0)
        self.im_mode = None
        self.im_tile = None
        self.im_palette = None

        self.text_memory = 0

    def check_text_memory(self, chunklen):
        self.text_memory += chunklen
        if self.text_memory > MAX_TEXT_MEMORY:
            raise ValueError("Too much memory used in text chunks: %s>MAX_TEXT_MEMORY" %
                             self.text_memory)

    def chunk_iCCP(self, pos, length):

        # ICC profile
        s = ImageFile._safe_read(self.fp, length)
        # according to PNG spec, the iCCP chunk contains:
        # Profile name  1-79 bytes (character string)
        # Null separator        1 byte (null character)
        # Compression method    1 byte (0)
        # Compressed profile    n bytes (zlib with deflate compression)
        i = s.find(b"\0")
        if Image.DEBUG:
            print("iCCP profile name", s[:i])
            print("Compression method", i8(s[i]))
        comp_method = i8(s[i])
        if comp_method != 0:
            raise SyntaxError("Unknown compression method %s in iCCP chunk" %
                              comp_method)
        try:
            icc_profile = _safe_zlib_decompress(s[i+2:])
        except zlib.error:
            icc_profile = None  # FIXME
        self.im_info["icc_profile"] = icc_profile
        return s

    def chunk_IHDR(self, pos, length):

        # image header
        s = ImageFile._safe_read(self.fp, length)
        self.im_size = i32(s), i32(s[4:])
        try:
            self.im_mode, self.im_rawmode = _MODES[(i8(s[8]), i8(s[9]))]
        except:
            pass
        if i8(s[12]):
            self.im_info["interlace"] = 1
        if i8(s[11]):
            raise SyntaxError("unknown filter category")
        return s

    def chunk_IDAT(self, pos, length):

        # image data
        self.im_tile = [("zip", (0, 0)+self.im_size, pos, self.im_rawmode)]
        self.im_idat = length
        raise EOFError

    def chunk_IEND(self, pos, length):

        # end of PNG image
        raise EOFError

    def chunk_PLTE(self, pos, length):

        # palette
        s = ImageFile._safe_read(self.fp, length)
        if self.im_mode == "P":
            self.im_palette = "RGB", s
        return s

    def chunk_tRNS(self, pos, length):

        # transparency
        s = ImageFile._safe_read(self.fp, length)
        if self.im_mode == "P":
            if _simple_palette.match(s):
                i = s.find(b"\0")
                if i >= 0:
                    self.im_info["transparency"] = i
            else:
                self.im_info["transparency"] = s
        elif self.im_mode == "L":
            self.im_info["transparency"] = i16(s)
        elif self.im_mode == "RGB":
            self.im_info["transparency"] = i16(s), i16(s[2:]), i16(s[4:])
        return s

    def chunk_gAMA(self, pos, length):

        # gamma setting
        s = ImageFile._safe_read(self.fp, length)
        self.im_info["gamma"] = i32(s) / 100000.0
        return s

    def chunk_pHYs(self, pos, length):

        # pixels per unit
        s = ImageFile._safe_read(self.fp, length)
        px, py = i32(s), i32(s[4:])
        unit = i8(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, length):

        # text
        s = ImageFile._safe_read(self.fp, length)
        try:
            k, v = s.split(b"\0", 1)
        except ValueError:
            # fallback for broken tEXt tags
            k = s
            v = b""
        if k:
            if bytes is not str:
                k = k.decode('latin-1', 'strict')
                v = v.decode('latin-1', 'replace')

            self.im_info[k] = self.im_text[k] = v
            self.check_text_memory(len(v))

        return s

    def chunk_zTXt(self, pos, length):

        # compressed text
        s = ImageFile._safe_read(self.fp, length)
        try:
            k, v = s.split(b"\0", 1)
        except ValueError:
            k = s
            v = b""
        if v:
            comp_method = i8(v[0])
        else:
            comp_method = 0
        if comp_method != 0:
            raise SyntaxError("Unknown compression method %s in zTXt chunk" %
                              comp_method)
        import zlib
        try:
            v = _safe_zlib_decompress(v[1:])
        except zlib.error:
            v = b""

        if k:
            if bytes is not str:
                k = k.decode('latin-1', 'strict')
                v = v.decode('latin-1', 'replace')

            self.im_info[k] = self.im_text[k] = v
            self.check_text_memory(len(v))

        return s

    def chunk_iTXt(self, pos, length):

        # international text
        r = s = ImageFile._safe_read(self.fp, length)
        try:
            k, r = r.split(b"\0", 1)
        except ValueError:
            return s
        if len(r) < 2:
            return s
        cf, cm, r = i8(r[0]), i8(r[1]), r[2:]
        try:
            lang, tk, v = r.split(b"\0", 2)
        except ValueError:
            return s
        if cf != 0:
            if cm == 0:
                import zlib
                try:
                    v = _safe_zlib_decompress(v)
                except zlib.error:
                    return s
            else:
                return s
        if bytes is not str:
            try:
                k = k.decode("latin-1", "strict")
                lang = lang.decode("utf-8", "strict")
                tk = tk.decode("utf-8", "strict")
                v = v.decode("utf-8", "strict")
            except UnicodeError:
                return s

        self.im_info[k] = self.im_text[k] = iTXt(v, lang, tk)
        self.check_text_memory(len(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 True:

            #
            # get next chunk

            cid, pos, length = self.png.read()

            try:
                s = self.png.call(cid, pos, length)
            except EOFError:
                break
            except AttributeError:
                if Image.DEBUG:
                    print(cid, pos, length, "(unknown)")
                s = ImageFile._safe_read(self.fp, length)

            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.text = self.png.im_text  # experimental
        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 = length  # 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"):
            self.decoderconfig = self.decoderconfig + (1,)

        ImageFile.ImageFile.load_prepare(self)

    def load_read(self, read_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, length = self.png.read()

            if cid not in [b"IDAT", b"DDAT"]:
                self.png.push(cid, pos, length)
                return b""

            self.__idat = length  # empty chunks are allowed

        # read more data from this chunk
        if read_bytes <= 0:
            read_bytes = self.__idat
        else:
            read_bytes = min(read_bytes, self.__idat)

        self.__idat = self.__idat - read_bytes

        return self.fp.read(read_bytes)

    def load_end(self):
        "internal: finished reading image data"

        self.png.close()
        self.png = None


# --------------------------------------------------------------------
# PNG writer

o8 = _binary.o8
o16 = _binary.o16be
o32 = _binary.o32be

_OUTMODES = {
    # supported PIL modes, and corresponding rawmodes/bits/color combinations
    "1":    ("1",       b'\x01\x00'),
    "L;1":  ("L;1",     b'\x01\x00'),
    "L;2":  ("L;2",     b'\x02\x00'),
    "L;4":  ("L;4",     b'\x04\x00'),
    "L":    ("L",       b'\x08\x00'),
    "LA":   ("LA",      b'\x08\x04'),
    "I":    ("I;16B",   b'\x10\x00'),
    "P;1":  ("P;1",     b'\x01\x03'),
    "P;2":  ("P;2",     b'\x02\x03'),
    "P;4":  ("P;4",     b'\x04\x03'),
    "P":    ("P",       b'\x08\x03'),
    "RGB":  ("RGB",     b'\x08\x02'),
    "RGBA": ("RGBA",    b'\x08\x06'),
}


def putchunk(fp, cid, *data):
    "Write a PNG chunk (including CRC field)"

    data = b"".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, b"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 "bits" in im.encoderinfo:
            # number of bits specified by user
            colors = 1 << im.encoderinfo["bits"]
        else:
            # check palette contents
            if im.palette:
                colors = max(min(len(im.palette.getdata()[1])//3, 256), 2)
            else:
                colors = 256

        if colors <= 2:
            bits = 1
        elif colors <= 4:
            bits = 2
        elif colors <= 16:
            bits = 4
        else:
            bits = 8
        if bits != 8:
            mode = "%s;%d" % (mode, bits)

    # encoder options
    if "dictionary" in im.encoderinfo:
        dictionary = im.encoderinfo["dictionary"]
    else:
        dictionary = b""

    im.encoderconfig = ("optimize" in im.encoderinfo,
                        im.encoderinfo.get("compress_level", -1),
                        im.encoderinfo.get("compress_type", -1),
                        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, b"IHDR",
          o32(im.size[0]), o32(im.size[1]),     # 0: size
          mode,                                 # 8: depth/type
          b'\0',                                # 10: compression
          b'\0',                                # 11: filter category
          b'\0')                                # 12: interlace flag

    if im.mode == "P":
        palette_byte_number = (2 ** bits) * 3
        palette_bytes = im.im.getpalette("RGB")[:palette_byte_number]
        while len(palette_bytes) < palette_byte_number:
            palette_bytes += b'\0'
        chunk(fp, b"PLTE", palette_bytes)

    transparency = im.encoderinfo.get('transparency',
                                      im.info.get('transparency', None))

    if transparency or transparency == 0:
        if im.mode == "P":
            # limit to actual palette size
            alpha_bytes = 2**bits
            if isinstance(transparency, bytes):
                chunk(fp, b"tRNS", transparency[:alpha_bytes])
            else:
                transparency = max(0, min(255, transparency))
                alpha = b'\xFF' * transparency + b'\0'
                chunk(fp, b"tRNS", alpha[:alpha_bytes])
        elif im.mode == "L":
            transparency = max(0, min(65535, transparency))
            chunk(fp, b"tRNS", o16(transparency))
        elif im.mode == "RGB":
            red, green, blue = transparency
            chunk(fp, b"tRNS", o16(red) + o16(green) + o16(blue))
        else:
            if "transparency" in im.encoderinfo:
                # don't bother with transparency if it's an RGBA
                # and it's in the info dict. It's probably just stale.
                raise IOError("cannot use transparency for this mode")
    else:
        if im.mode == "P" and im.im.getpalettemode() == "RGBA":
            alpha = im.im.getpalette("RGBA", "A")
            alpha_bytes = 2**bits
            chunk(fp, b"tRNS", alpha[:alpha_bytes])

    if 0:
        # FIXME: to be supported some day
        chunk(fp, b"gAMA", o32(int(gamma * 100000.0)))

    dpi = im.encoderinfo.get("dpi")
    if dpi:
        chunk(fp, b"pHYs",
              o32(int(dpi[0] / 0.0254 + 0.5)),
              o32(int(dpi[1] / 0.0254 + 0.5)),
              b'\x01')

    info = im.encoderinfo.get("pnginfo")
    if info:
        for cid, data in info.chunks:
            chunk(fp, cid, data)

    # ICC profile writing support -- 2008-06-06 Florian Hoech
    if im.info.get("icc_profile"):
        # ICC profile
        # according to PNG spec, the iCCP chunk contains:
        # Profile name  1-79 bytes (character string)
        # Null separator        1 byte (null character)
        # Compression method    1 byte (0)
        # Compressed profile    n bytes (zlib with deflate compression)
        name = b"ICC Profile"
        data = name + b"\0\0" + zlib.compress(im.info["icc_profile"])
        chunk(fp, b"iCCP", data)

    ImageFile._save(im, _idat(fp, chunk),
                    [("zip", (0, 0)+im.size, 0, rawmode)])

    chunk(fp, b"IEND", b"")

    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 = b"".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")