PIL.PngImagePlugin 源代码
#
# 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.
#
import itertools
import logging
import re
import struct
import warnings
import zlib
from . import Image, ImageChops, ImageFile, ImagePalette, ImageSequence
from ._binary import i16be as i16
from ._binary import i32be as i32
from ._binary import o8
from ._binary import o16be as o16
from ._binary import o32be as o32
logger = logging.getLogger(__name__)
is_cid = re.compile(br"\w\w\w\w").match
_MAGIC = b"\211PNG\r\n\032\n"
_MODES = {
# supported bits/color combinations, and corresponding modes/rawmodes
# Greyscale
(1, 0): ("1", "1"),
(2, 0): ("L", "L;2"),
(4, 0): ("L", "L;4"),
(8, 0): ("L", "L"),
(16, 0): ("I", "I;16B"),
# Truecolour
(8, 2): ("RGB", "RGB"),
(16, 2): ("RGB", "RGB;16B"),
# Indexed-colour
(1, 3): ("P", "P;1"),
(2, 3): ("P", "P;2"),
(4, 3): ("P", "P;4"),
(8, 3): ("P", "P"),
# Greyscale with alpha
(8, 4): ("LA", "LA"),
(16, 4): ("RGBA", "LA;16B"), # LA;16B->LA not yet available
# Truecolour with alpha
(8, 6): ("RGBA", "RGBA"),
(16, 6): ("RGBA", "RGBA;16B"),
}
_simple_palette = re.compile(b"^\xff*\x00\xff*$")
MAX_TEXT_CHUNK = ImageFile.SAFEBLOCK
"""
Maximum decompressed size for a iTXt or zTXt chunk.
Eliminates decompression bombs where compressed chunks can expand 1000x.
See :ref:`Text in PNG File Format<png-text>`.
"""
MAX_TEXT_MEMORY = 64 * MAX_TEXT_CHUNK
"""
Set the maximum total text chunk size.
See :ref:`Text in PNG File Format<png-text>`.
"""
# APNG frame disposal modes
APNG_DISPOSE_OP_NONE = 0
"""
No disposal is done on this frame before rendering the next frame.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
APNG_DISPOSE_OP_BACKGROUND = 1
"""
This frame’s modified region is cleared to fully transparent black before rendering
the next frame.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
APNG_DISPOSE_OP_PREVIOUS = 2
"""
This frame’s modified region is reverted to the previous frame’s contents before
rendering the next frame.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
# APNG frame blend modes
APNG_BLEND_OP_SOURCE = 0
"""
All color components of this frame, including alpha, overwrite the previous output
image contents.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
APNG_BLEND_OP_OVER = 1
"""
This frame should be alpha composited with the previous output image contents.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
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
def _crc32(data, seed=0):
return zlib.crc32(data, seed) & 0xFFFFFFFF
# --------------------------------------------------------------------
# Support classes. Suitable for PNG and related formats like MNG etc.
[文档]class ChunkStream:
def __init__(self, fp):
self.fp = fp
self.queue = []
[文档] def read(self):
"""Fetch a new chunk. Returns header information."""
cid = None
if self.queue:
cid, pos, length = self.queue.pop()
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):
if not ImageFile.LOAD_TRUNCATED_IMAGES:
raise SyntaxError(f"broken PNG file (chunk {repr(cid)})")
return cid, pos, length
def __enter__(self):
return self
def __exit__(self, *args):
self.close()
[文档] def call(self, cid, pos, length):
"""Call the appropriate chunk handler"""
logger.debug("STREAM %r %s %s", cid, pos, length)
return getattr(self, "chunk_" + cid.decode("ascii"))(pos, length)
[文档] def crc(self, cid, data):
"""Read and verify checksum"""
# Skip CRC checks for ancillary chunks if allowed to load truncated
# images
# 5th byte of first char is 1 [specs, section 5.4]
if ImageFile.LOAD_TRUNCATED_IMAGES and (cid[0] >> 5 & 1):
self.crc_skip(cid, data)
return
try:
crc1 = _crc32(data, _crc32(cid))
crc2 = i32(self.fp.read(4))
if crc1 != crc2:
raise SyntaxError(
f"broken PNG file (bad header checksum in {repr(cid)})"
)
except struct.error as e:
raise SyntaxError(
f"broken PNG file (incomplete checksum in {repr(cid)})"
) from e
[文档] def crc_skip(self, cid, data):
"""Read checksum. Used if the C module is not present"""
self.fp.read(4)
[文档] def verify(self, endchunk=b"IEND"):
# Simple approach; just calculate checksum for all remaining
# blocks. Must be called directly after open.
cids = []
while True:
try:
cid, pos, length = self.read()
except struct.error as e:
raise OSError("truncated PNG file") from e
if cid == endchunk:
break
self.crc(cid, ImageFile._safe_read(self.fp, length))
cids.append(cid)
return cids
[文档]class iTXt(str):
"""
Subclass of string to allow iTXt chunks to look like strings while
keeping their extra information
"""
[文档] @staticmethod
def __new__(cls, text, lang=None, tkey=None):
"""
:param cls: the class to use when creating the instance
:param text: value for this key
:param lang: language code
:param tkey: UTF-8 version of the key name
"""
self = str.__new__(cls, text)
self.lang = lang
self.tkey = tkey
return self
[文档]class PngInfo:
"""
PNG chunk container (for use with save(pnginfo=))
"""
def __init__(self):
self.chunks = []
[文档] def add(self, cid, data, after_idat=False):
"""Appends an arbitrary chunk. Use with caution.
:param cid: a byte string, 4 bytes long.
:param data: a byte string of the encoded data
:param after_idat: for use with private chunks. Whether the chunk
should be written after IDAT
"""
chunk = [cid, data]
if after_idat:
chunk.append(True)
self.chunks.append(tuple(chunk))
[文档] def add_itxt(self, key, value, lang="", tkey="", zip=False):
"""Appends an iTXt chunk.
:param key: latin-1 encodable text key name
:param value: value for this key
:param lang: language code
:param tkey: UTF-8 version of the key name
:param zip: compression flag
"""
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:
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)
[文档] def add_text(self, key, value, zip=False):
"""Appends a text chunk.
:param key: latin-1 encodable text key name
:param value: value for this key, text or an
:py:class:`PIL.PngImagePlugin.iTXt` instance
:param zip: compression flag
"""
if isinstance(value, iTXt):
return self.add_itxt(key, value, value.lang, value.tkey, zip=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=zip)
if not isinstance(key, bytes):
key = key.encode("latin-1", "strict")
if zip:
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)
[文档]class PngStream(ChunkStream):
def __init__(self, fp):
super().__init__(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.im_custom_mimetype = None
self.im_n_frames = None
self._seq_num = None
self.rewind_state = None
self.text_memory = 0
[文档] 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: "
f"{self.text_memory}>MAX_TEXT_MEMORY"
)
[文档] def save_rewind(self):
self.rewind_state = {
"info": self.im_info.copy(),
"tile": self.im_tile,
"seq_num": self._seq_num,
}
[文档] def rewind(self):
self.im_info = self.rewind_state["info"]
self.im_tile = self.rewind_state["tile"]
self._seq_num = self.rewind_state["seq_num"]
[文档] 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")
logger.debug("iCCP profile name %r", s[:i])
logger.debug("Compression method %s", s[i])
comp_method = s[i]
if comp_method != 0:
raise SyntaxError(f"Unknown compression method {comp_method} in iCCP chunk")
try:
icc_profile = _safe_zlib_decompress(s[i + 2 :])
except ValueError:
if ImageFile.LOAD_TRUNCATED_IMAGES:
icc_profile = None
else:
raise
except zlib.error:
icc_profile = None # FIXME
self.im_info["icc_profile"] = icc_profile
return s
[文档] def chunk_IHDR(self, pos, length):
# image header
s = ImageFile._safe_read(self.fp, length)
self.im_size = i32(s, 0), i32(s, 4)
try:
self.im_mode, self.im_rawmode = _MODES[(s[8], s[9])]
except Exception:
pass
if s[12]:
self.im_info["interlace"] = 1
if s[11]:
raise SyntaxError("unknown filter category")
return s
[文档] def chunk_IDAT(self, pos, length):
# image data
if "bbox" in self.im_info:
tile = [("zip", self.im_info["bbox"], pos, self.im_rawmode)]
else:
if self.im_n_frames is not None:
self.im_info["default_image"] = True
tile = [("zip", (0, 0) + self.im_size, pos, self.im_rawmode)]
self.im_tile = tile
self.im_idat = length
raise EOFError
[文档] 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
[文档] def chunk_tRNS(self, pos, length):
# transparency
s = ImageFile._safe_read(self.fp, length)
if self.im_mode == "P":
if _simple_palette.match(s):
# tRNS contains only one full-transparent entry,
# other entries are full opaque
i = s.find(b"\0")
if i >= 0:
self.im_info["transparency"] = i
else:
# otherwise, we have a byte string with one alpha value
# for each palette entry
self.im_info["transparency"] = s
elif self.im_mode in ("1", "L", "I"):
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
[文档] 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
[文档] def chunk_cHRM(self, pos, length):
# chromaticity, 8 unsigned ints, actual value is scaled by 100,000
# WP x,y, Red x,y, Green x,y Blue x,y
s = ImageFile._safe_read(self.fp, length)
raw_vals = struct.unpack(">%dI" % (len(s) // 4), s)
self.im_info["chromaticity"] = tuple(elt / 100000.0 for elt in raw_vals)
return s
[文档] def chunk_sRGB(self, pos, length):
# srgb rendering intent, 1 byte
# 0 perceptual
# 1 relative colorimetric
# 2 saturation
# 3 absolute colorimetric
s = ImageFile._safe_read(self.fp, length)
self.im_info["srgb"] = s[0]
return s
[文档] def chunk_pHYs(self, pos, length):
# pixels per unit
s = ImageFile._safe_read(self.fp, length)
px, py = i32(s, 0), i32(s, 4)
unit = s[8]
if unit == 1: # meter
dpi = px * 0.0254, py * 0.0254
self.im_info["dpi"] = dpi
elif unit == 0:
self.im_info["aspect"] = px, py
return s
[文档] 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:
k = k.decode("latin-1", "strict")
v_str = v.decode("latin-1", "replace")
self.im_info[k] = v if k == "exif" else v_str
self.im_text[k] = v_str
self.check_text_memory(len(v_str))
return s
[文档] 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 = v[0]
else:
comp_method = 0
if comp_method != 0:
raise SyntaxError(f"Unknown compression method {comp_method} in zTXt chunk")
try:
v = _safe_zlib_decompress(v[1:])
except ValueError:
if ImageFile.LOAD_TRUNCATED_IMAGES:
v = b""
else:
raise
except zlib.error:
v = b""
if k:
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
[文档] 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 = r[0], r[1], r[2:]
try:
lang, tk, v = r.split(b"\0", 2)
except ValueError:
return s
if cf != 0:
if cm == 0:
try:
v = _safe_zlib_decompress(v)
except ValueError:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
else:
raise
except zlib.error:
return s
else:
return s
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
[文档] def chunk_eXIf(self, pos, length):
s = ImageFile._safe_read(self.fp, length)
self.im_info["exif"] = b"Exif\x00\x00" + s
return s
# APNG chunks
[文档] def chunk_acTL(self, pos, length):
s = ImageFile._safe_read(self.fp, length)
if self.im_n_frames is not None:
self.im_n_frames = None
warnings.warn("Invalid APNG, will use default PNG image if possible")
return s
n_frames = i32(s)
if n_frames == 0 or n_frames > 0x80000000:
warnings.warn("Invalid APNG, will use default PNG image if possible")
return s
self.im_n_frames = n_frames
self.im_info["loop"] = i32(s, 4)
self.im_custom_mimetype = "image/apng"
return s
[文档] def chunk_fcTL(self, pos, length):
s = ImageFile._safe_read(self.fp, length)
seq = i32(s)
if (self._seq_num is None and seq != 0) or (
self._seq_num is not None and self._seq_num != seq - 1
):
raise SyntaxError("APNG contains frame sequence errors")
self._seq_num = seq
width, height = i32(s, 4), i32(s, 8)
px, py = i32(s, 12), i32(s, 16)
im_w, im_h = self.im_size
if px + width > im_w or py + height > im_h:
raise SyntaxError("APNG contains invalid frames")
self.im_info["bbox"] = (px, py, px + width, py + height)
delay_num, delay_den = i16(s, 20), i16(s, 22)
if delay_den == 0:
delay_den = 100
self.im_info["duration"] = float(delay_num) / float(delay_den) * 1000
self.im_info["disposal"] = s[24]
self.im_info["blend"] = s[25]
return s
[文档] def chunk_fdAT(self, pos, length):
s = ImageFile._safe_read(self.fp, 4)
seq = i32(s)
if self._seq_num != seq - 1:
raise SyntaxError("APNG contains frame sequence errors")
self._seq_num = seq
return self.chunk_IDAT(pos + 4, length - 4)
# --------------------------------------------------------------------
# PNG reader
def _accept(prefix):
return prefix[:8] == _MAGIC
##
# Image plugin for PNG images.
[文档]class PngImageFile(ImageFile.ImageFile):
format = "PNG"
format_description = "Portable network graphics"
def _open(self):
if not _accept(self.fp.read(8)):
raise SyntaxError("not a PNG file")
self.__fp = self.fp
self.__frame = 0
#
# Parse headers up to the first IDAT or fDAT chunk
self.private_chunks = []
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:
logger.debug("%r %s %s (unknown)", cid, pos, length)
s = ImageFile._safe_read(self.fp, length)
if cid[1:2].islower():
self.private_chunks.append((cid, s))
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 = None
self.tile = self.png.im_tile
self.custom_mimetype = self.png.im_custom_mimetype
self.n_frames = self.png.im_n_frames or 1
self.default_image = self.info.get("default_image", False)
if self.png.im_palette:
rawmode, data = self.png.im_palette
self.palette = ImagePalette.raw(rawmode, data)
if cid == b"fdAT":
self.__prepare_idat = length - 4
else:
self.__prepare_idat = length # used by load_prepare()
if self.png.im_n_frames is not None:
self._close_exclusive_fp_after_loading = False
self.png.save_rewind()
self.__rewind_idat = self.__prepare_idat
self.__rewind = self.__fp.tell()
if self.default_image:
# IDAT chunk contains default image and not first animation frame
self.n_frames += 1
self._seek(0)
self.is_animated = self.n_frames > 1
@property
def text(self):
# experimental
if self._text is None:
# iTxt, tEXt and zTXt chunks may appear at the end of the file
# So load the file to ensure that they are read
if self.is_animated:
frame = self.__frame
# for APNG, seek to the final frame before loading
self.seek(self.n_frames - 1)
self.load()
if self.is_animated:
self.seek(frame)
return self._text
[文档] 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()
if self._exclusive_fp:
self.fp.close()
self.fp = None
[文档] def seek(self, frame):
if not self._seek_check(frame):
return
if frame < self.__frame:
self._seek(0, True)
last_frame = self.__frame
for f in range(self.__frame + 1, frame + 1):
try:
self._seek(f)
except EOFError as e:
self.seek(last_frame)
raise EOFError("no more images in APNG file") from e
def _seek(self, frame, rewind=False):
if frame == 0:
if rewind:
self.__fp.seek(self.__rewind)
self.png.rewind()
self.__prepare_idat = self.__rewind_idat
self.im = None
if self.pyaccess:
self.pyaccess = None
self.info = self.png.im_info
self.tile = self.png.im_tile
self.fp = self.__fp
self._prev_im = None
self.dispose = None
self.default_image = self.info.get("default_image", False)
self.dispose_op = self.info.get("disposal")
self.blend_op = self.info.get("blend")
self.dispose_extent = self.info.get("bbox")
self.__frame = 0
else:
if frame != self.__frame + 1:
raise ValueError(f"cannot seek to frame {frame}")
# ensure previous frame was loaded
self.load()
if self.dispose:
self.im.paste(self.dispose, self.dispose_extent)
self._prev_im = self.im.copy()
self.fp = self.__fp
# advance to the next frame
if self.__prepare_idat:
ImageFile._safe_read(self.fp, self.__prepare_idat)
self.__prepare_idat = 0
frame_start = False
while True:
self.fp.read(4) # CRC
try:
cid, pos, length = self.png.read()
except (struct.error, SyntaxError):
break
if cid == b"IEND":
raise EOFError("No more images in APNG file")
if cid == b"fcTL":
if frame_start:
# there must be at least one fdAT chunk between fcTL chunks
raise SyntaxError("APNG missing frame data")
frame_start = True
try:
self.png.call(cid, pos, length)
except UnicodeDecodeError:
break
except EOFError:
if cid == b"fdAT":
length -= 4
if frame_start:
self.__prepare_idat = length
break
ImageFile._safe_read(self.fp, length)
except AttributeError:
logger.debug("%r %s %s (unknown)", cid, pos, length)
ImageFile._safe_read(self.fp, length)
self.__frame = frame
self.tile = self.png.im_tile
self.dispose_op = self.info.get("disposal")
self.blend_op = self.info.get("blend")
self.dispose_extent = self.info.get("bbox")
if not self.tile:
raise EOFError
# setup frame disposal (actual disposal done when needed in the next _seek())
if self._prev_im is None and self.dispose_op == APNG_DISPOSE_OP_PREVIOUS:
self.dispose_op = APNG_DISPOSE_OP_BACKGROUND
if self.dispose_op == APNG_DISPOSE_OP_PREVIOUS:
self.dispose = self._prev_im.copy()
self.dispose = self._crop(self.dispose, self.dispose_extent)
elif self.dispose_op == APNG_DISPOSE_OP_BACKGROUND:
self.dispose = Image.core.fill(self.mode, self.size)
self.dispose = self._crop(self.dispose, self.dispose_extent)
else:
self.dispose = None
[文档] def load_prepare(self):
"""internal: prepare to read PNG file"""
if self.info.get("interlace"):
self.decoderconfig = self.decoderconfig + (1,)
self.__idat = self.__prepare_idat # used by load_read()
ImageFile.ImageFile.load_prepare(self)
[文档] 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", b"fdAT"]:
self.png.push(cid, pos, length)
return b""
if cid == b"fdAT":
try:
self.png.call(cid, pos, length)
except EOFError:
pass
self.__idat = length - 4 # sequence_num has already been read
else:
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)
[文档] def load_end(self):
"""internal: finished reading image data"""
if self.__idat != 0:
self.fp.read(self.__idat)
while True:
self.fp.read(4) # CRC
try:
cid, pos, length = self.png.read()
except (struct.error, SyntaxError):
break
if cid == b"IEND":
break
elif cid == b"fcTL" and self.is_animated:
# start of the next frame, stop reading
self.__prepare_idat = 0
self.png.push(cid, pos, length)
break
try:
self.png.call(cid, pos, length)
except UnicodeDecodeError:
break
except EOFError:
if cid == b"fdAT":
length -= 4
ImageFile._safe_read(self.fp, length)
except AttributeError:
logger.debug("%r %s %s (unknown)", cid, pos, length)
s = ImageFile._safe_read(self.fp, length)
if cid[1:2].islower():
self.private_chunks.append((cid, s, True))
self._text = self.png.im_text
if not self.is_animated:
self.png.close()
self.png = None
else:
if self._prev_im and self.blend_op == APNG_BLEND_OP_OVER:
updated = self._crop(self.im, self.dispose_extent)
self._prev_im.paste(
updated, self.dispose_extent, updated.convert("RGBA")
)
self.im = self._prev_im
if self.pyaccess:
self.pyaccess = None
def _getexif(self):
if "exif" not in self.info:
self.load()
if "exif" not in self.info and "Raw profile type exif" not in self.info:
return None
return self.getexif()._get_merged_dict()
[文档] def getxmp(self):
"""
Returns a dictionary containing the XMP tags.
Requires defusedxml to be installed.
:returns: XMP tags in a dictionary.
"""
return (
self._getxmp(self.info["XML:com.adobe.xmp"])
if "XML:com.adobe.xmp" in self.info
else {}
)
def _close__fp(self):
try:
if self.__fp != self.fp:
self.__fp.close()
except AttributeError:
pass
finally:
self.__fp = None
# --------------------------------------------------------------------
# PNG writer
_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"),
"I;16": ("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"),
}
[文档]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)
crc = _crc32(data, _crc32(cid))
fp.write(o32(crc))
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)
class _fdat:
# wrap encoder output in fdAT chunks
def __init__(self, fp, chunk, seq_num):
self.fp = fp
self.chunk = chunk
self.seq_num = seq_num
def write(self, data):
self.chunk(self.fp, b"fdAT", o32(self.seq_num), data)
self.seq_num += 1
def _write_multiple_frames(im, fp, chunk, rawmode):
default_image = im.encoderinfo.get("default_image", im.info.get("default_image"))
duration = im.encoderinfo.get("duration", im.info.get("duration", 0))
loop = im.encoderinfo.get("loop", im.info.get("loop", 0))
disposal = im.encoderinfo.get(
"disposal", im.info.get("disposal", APNG_DISPOSE_OP_NONE)
)
blend = im.encoderinfo.get("blend", im.info.get("blend", APNG_BLEND_OP_SOURCE))
if default_image:
chain = itertools.chain(im.encoderinfo.get("append_images", []))
else:
chain = itertools.chain([im], im.encoderinfo.get("append_images", []))
im_frames = []
frame_count = 0
for im_seq in chain:
for im_frame in ImageSequence.Iterator(im_seq):
im_frame = im_frame.copy()
if im_frame.mode != im.mode:
if im.mode == "P":
im_frame = im_frame.convert(im.mode, palette=im.palette)
else:
im_frame = im_frame.convert(im.mode)
encoderinfo = im.encoderinfo.copy()
if isinstance(duration, (list, tuple)):
encoderinfo["duration"] = duration[frame_count]
if isinstance(disposal, (list, tuple)):
encoderinfo["disposal"] = disposal[frame_count]
if isinstance(blend, (list, tuple)):
encoderinfo["blend"] = blend[frame_count]
frame_count += 1
if im_frames:
previous = im_frames[-1]
prev_disposal = previous["encoderinfo"].get("disposal")
prev_blend = previous["encoderinfo"].get("blend")
if prev_disposal == APNG_DISPOSE_OP_PREVIOUS and len(im_frames) < 2:
prev_disposal = APNG_DISPOSE_OP_BACKGROUND
if prev_disposal == APNG_DISPOSE_OP_BACKGROUND:
base_im = previous["im"]
dispose = Image.core.fill("RGBA", im.size, (0, 0, 0, 0))
bbox = previous["bbox"]
if bbox:
dispose = dispose.crop(bbox)
else:
bbox = (0, 0) + im.size
base_im.paste(dispose, bbox)
elif prev_disposal == APNG_DISPOSE_OP_PREVIOUS:
base_im = im_frames[-2]["im"]
else:
base_im = previous["im"]
delta = ImageChops.subtract_modulo(
im_frame.convert("RGB"), base_im.convert("RGB")
)
bbox = delta.getbbox()
if (
not bbox
and prev_disposal == encoderinfo.get("disposal")
and prev_blend == encoderinfo.get("blend")
):
if isinstance(duration, (list, tuple)):
previous["encoderinfo"]["duration"] += encoderinfo["duration"]
continue
else:
bbox = None
im_frames.append({"im": im_frame, "bbox": bbox, "encoderinfo": encoderinfo})
# animation control
chunk(
fp,
b"acTL",
o32(len(im_frames)), # 0: num_frames
o32(loop), # 4: num_plays
)
# default image IDAT (if it exists)
if default_image:
ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)])
seq_num = 0
for frame, frame_data in enumerate(im_frames):
im_frame = frame_data["im"]
if not frame_data["bbox"]:
bbox = (0, 0) + im_frame.size
else:
bbox = frame_data["bbox"]
im_frame = im_frame.crop(bbox)
size = im_frame.size
encoderinfo = frame_data["encoderinfo"]
frame_duration = int(round(encoderinfo.get("duration", duration)))
frame_disposal = encoderinfo.get("disposal", disposal)
frame_blend = encoderinfo.get("blend", blend)
# frame control
chunk(
fp,
b"fcTL",
o32(seq_num), # sequence_number
o32(size[0]), # width
o32(size[1]), # height
o32(bbox[0]), # x_offset
o32(bbox[1]), # y_offset
o16(frame_duration), # delay_numerator
o16(1000), # delay_denominator
o8(frame_disposal), # dispose_op
o8(frame_blend), # blend_op
)
seq_num += 1
# frame data
if frame == 0 and not default_image:
# first frame must be in IDAT chunks for backwards compatibility
ImageFile._save(
im_frame,
_idat(fp, chunk),
[("zip", (0, 0) + im_frame.size, 0, rawmode)],
)
else:
fdat_chunks = _fdat(fp, chunk, seq_num)
ImageFile._save(
im_frame,
fdat_chunks,
[("zip", (0, 0) + im_frame.size, 0, rawmode)],
)
seq_num = fdat_chunks.seq_num
def _save_all(im, fp, filename):
_save(im, fp, filename, save_all=True)
def _save(im, fp, filename, chunk=putchunk, save_all=False):
# 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 = min(1 << im.encoderinfo["bits"], 256)
else:
# check palette contents
if im.palette:
colors = max(min(len(im.palette.getdata()[1]) // 3, 256), 1)
else:
colors = 256
if colors <= 16:
if colors <= 2:
bits = 1
elif colors <= 4:
bits = 2
else:
bits = 4
mode = f"{mode};{bits}"
# encoder options
im.encoderconfig = (
im.encoderinfo.get("optimize", False),
im.encoderinfo.get("compress_level", -1),
im.encoderinfo.get("compress_type", -1),
im.encoderinfo.get("dictionary", b""),
)
# get the corresponding PNG mode
try:
rawmode, mode = _OUTMODES[mode]
except KeyError as e:
raise OSError(f"cannot write mode {mode} as PNG") from e
#
# write minimal PNG file
fp.write(_MAGIC)
chunk(
fp,
b"IHDR",
o32(im.size[0]), # 0: size
o32(im.size[1]),
mode, # 8: depth/type
b"\0", # 10: compression
b"\0", # 11: filter category
b"\0", # 12: interlace flag
)
chunks = [b"cHRM", b"gAMA", b"sBIT", b"sRGB", b"tIME"]
icc = im.encoderinfo.get("icc_profile", im.info.get("icc_profile"))
if icc:
# 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(icc)
chunk(fp, b"iCCP", data)
# You must either have sRGB or iCCP.
# Disallow sRGB chunks when an iCCP-chunk has been emitted.
chunks.remove(b"sRGB")
info = im.encoderinfo.get("pnginfo")
if info:
chunks_multiple_allowed = [b"sPLT", b"iTXt", b"tEXt", b"zTXt"]
for info_chunk in info.chunks:
cid, data = info_chunk[:2]
if cid in chunks:
chunks.remove(cid)
chunk(fp, cid, data)
elif cid in chunks_multiple_allowed:
chunk(fp, cid, data)
elif cid[1:2].islower():
# Private chunk
after_idat = info_chunk[2:3]
if not after_idat:
chunk(fp, cid, data)
if im.mode == "P":
palette_byte_number = colors * 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 = colors
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 in ("1", "L", "I"):
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 OSError("cannot use transparency for this mode")
else:
if im.mode == "P" and im.im.getpalettemode() == "RGBA":
alpha = im.im.getpalette("RGBA", "A")
alpha_bytes = colors
chunk(fp, b"tRNS", alpha[:alpha_bytes])
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",
)
if info:
chunks = [b"bKGD", b"hIST"]
for info_chunk in info.chunks:
cid, data = info_chunk[:2]
if cid in chunks:
chunks.remove(cid)
chunk(fp, cid, data)
exif = im.encoderinfo.get("exif", im.info.get("exif"))
if exif:
if isinstance(exif, Image.Exif):
exif = exif.tobytes(8)
if exif.startswith(b"Exif\x00\x00"):
exif = exif[6:]
chunk(fp, b"eXIf", exif)
if save_all:
_write_multiple_frames(im, fp, chunk, rawmode)
else:
ImageFile._save(im, _idat(fp, chunk), [("zip", (0, 0) + im.size, 0, rawmode)])
if info:
for info_chunk in info.chunks:
cid, data = info_chunk[:2]
if cid[1:2].islower():
# Private chunk
after_idat = info_chunk[2:3]
if after_idat:
chunk(fp, cid, data)
chunk(fp, b"IEND", b"")
if hasattr(fp, "flush"):
fp.flush()
# --------------------------------------------------------------------
# PNG chunk converter
[文档]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)
crc = o32(_crc32(data, _crc32(cid)))
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(PngImageFile.format, PngImageFile, _accept)
Image.register_save(PngImageFile.format, _save)
Image.register_save_all(PngImageFile.format, _save_all)
Image.register_extensions(PngImageFile.format, [".png", ".apng"])
Image.register_mime(PngImageFile.format, "image/png")
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