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Copy pathPngImagePlugin.py
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1609 lines (1373 loc) · 52.5 KB
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#
# 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 annotations
__lazy_modules__ = {
"PIL._binary",
"PIL._util",
"fractions",
"itertools",
"struct",
"warnings",
"zlib",
}
import itertools
import logging
import re
import struct
import warnings
import zlib
from enum import IntEnum
from fractions import Fraction
from typing import IO, NamedTuple, cast
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
from ._util import DeferredError
TYPE_CHECKING = False
if TYPE_CHECKING:
from collections.abc import Callable
from typing import Any, NoReturn, Self
from . import _imaging
logger = logging.getLogger(__name__)
is_cid = re.compile(rb"\w\w\w\w").match
_MAGIC = b"\211PNG\r\n\032\n"
_MODES = {
# supported bits/color combinations, and corresponding modes/rawmodes
# Grayscale
(1, 0): ("1", "1"),
(2, 0): ("L", "L;2"),
(4, 0): ("L", "L;4"),
(8, 0): ("L", "L"),
(16, 0): ("I;16", "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"),
# Grayscale 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
class Disposal(IntEnum):
OP_NONE = 0
"""
No disposal is done on this frame before rendering the next frame.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
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>`.
"""
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
class Blend(IntEnum):
OP_SOURCE = 0
"""
All color components of this frame, including alpha, overwrite the previous output
image contents.
See :ref:`Saving APNG sequences<apng-saving>`.
"""
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: bytes) -> bytes:
dobj = zlib.decompressobj()
plaintext = dobj.decompress(s, MAX_TEXT_CHUNK)
if dobj.unconsumed_tail:
msg = "Decompressed data too large for PngImagePlugin.MAX_TEXT_CHUNK"
raise ValueError(msg)
return plaintext
def _crc32(data: bytes, seed: int = 0) -> int:
return zlib.crc32(data, seed) & 0xFFFFFFFF
# --------------------------------------------------------------------
# Support classes. Suitable for PNG and related formats like MNG etc.
class ChunkStream:
def __init__(self, fp: IO[bytes]) -> None:
self.fp: IO[bytes] | None = fp
self.queue: list[tuple[bytes, int, int]] | None = []
def read(self) -> tuple[bytes, int, int]:
"""Fetch a new chunk. Returns header information."""
cid = None
assert self.fp is not 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:
msg = f"broken PNG file (chunk {repr(cid)})"
raise SyntaxError(msg)
return cid, pos, length
def __enter__(self) -> Self:
return self
def __exit__(self, *args: object) -> None:
self.close()
def close(self) -> None:
self.queue = self.fp = None
def push(self, cid: bytes, pos: int, length: int) -> None:
assert self.queue is not None
self.queue.append((cid, pos, length))
def call(self, cid: bytes, pos: int, length: int) -> bytes:
"""Call the appropriate chunk handler"""
logger.debug("STREAM %r %s %s", cid, pos, length)
return getattr(self, f"chunk_{cid.decode('ascii')}")(pos, length)
def crc(self, cid: bytes, data: bytes) -> None:
"""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
assert self.fp is not None
try:
crc1 = _crc32(data, _crc32(cid))
crc2 = i32(self.fp.read(4))
if crc1 != crc2:
msg = f"broken PNG file (bad header checksum in {repr(cid)})"
raise SyntaxError(msg)
except struct.error as e:
msg = f"broken PNG file (incomplete checksum in {repr(cid)})"
raise SyntaxError(msg) from e
def crc_skip(self, cid: bytes, data: bytes) -> None:
"""Read checksum"""
assert self.fp is not None
self.fp.read(4)
def verify(self, endchunk: bytes = b"IEND") -> list[bytes]:
# Simple approach; just calculate checksum for all remaining
# blocks. Must be called directly after open.
cids = []
assert self.fp is not None
while True:
try:
cid, pos, length = self.read()
except struct.error as e:
msg = "truncated PNG file"
raise OSError(msg) from e
if cid == endchunk:
break
self.crc(cid, ImageFile._safe_read(self.fp, length))
cids.append(cid)
return cids
class iTXt(str):
"""
Subclass of string to allow iTXt chunks to look like strings while
keeping their extra information
"""
lang: str | bytes | None
tkey: str | bytes | None
@staticmethod
def __new__(
cls, text: str, lang: str | None = None, tkey: str | None = None
) -> Self:
"""
: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
class PngInfo:
"""
PNG chunk container (for use with save(pnginfo=))
"""
def __init__(self) -> None:
self.chunks: list[tuple[bytes, bytes, bool]] = []
def add(self, cid: bytes, data: bytes, after_idat: bool = False) -> None:
"""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
"""
self.chunks.append((cid, data, after_idat))
def add_itxt(
self,
key: str | bytes,
value: str | bytes,
lang: str | bytes = "",
tkey: str | bytes = "",
zip: bool = False,
) -> None:
"""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)
def add_text(
self, key: str | bytes, value: str | bytes | iTXt, zip: bool = False
) -> None:
"""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 if value.lang is not None else b"",
value.tkey if value.tkey is not None else b"",
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)
class _RewindState(NamedTuple):
info: dict[str | tuple[int, int], Any]
tile: list[ImageFile._Tile]
seq_num: int | None
class PngStream(ChunkStream):
def __init__(self, fp: IO[bytes]) -> None:
super().__init__(fp)
# local copies of Image attributes
self.im_info: dict[str | tuple[int, int], Any] = {}
self.im_text: dict[str, str | iTXt] = {}
self.im_size = (0, 0)
self.im_mode = ""
self.im_tile: list[ImageFile._Tile] = []
self.im_palette: tuple[str, bytes] | None = None
self.im_custom_mimetype: str | None = None
self.im_n_frames: int | None = None
self._seq_num: int | None = None
self.rewind_state = _RewindState({}, [], None)
self.text_memory = 0
def check_text_memory(self, chunklen: int) -> None:
self.text_memory += chunklen
if self.text_memory > MAX_TEXT_MEMORY:
msg = (
"Too much memory used in text chunks: "
f"{self.text_memory}>MAX_TEXT_MEMORY"
)
raise ValueError(msg)
def save_rewind(self) -> None:
self.rewind_state = _RewindState(
self.im_info.copy(),
self.im_tile,
self._seq_num,
)
def rewind(self) -> None:
self.im_info = self.rewind_state.info.copy()
self.im_tile = self.rewind_state.tile
self._seq_num = self.rewind_state.seq_num
def chunk_iCCP(self, pos: int, length: int) -> bytes:
# ICC profile
assert self.fp is not None
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])
comp_method = s[i + 1]
logger.debug("Compression method %s", comp_method)
if comp_method != 0:
msg = f"Unknown compression method {comp_method} in iCCP chunk"
raise SyntaxError(msg)
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
def chunk_IHDR(self, pos: int, length: int) -> bytes:
# image header
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 13:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated IHDR chunk"
raise ValueError(msg)
self.im_size = i32(s, 0), i32(s, 4)
try:
self.im_mode, self.im_rawmode = _MODES[(s[8], s[9])]
except KeyError:
pass
if s[12]:
self.im_info["interlace"] = 1
if s[11]:
msg = "unknown filter category"
raise SyntaxError(msg)
return s
def chunk_IDAT(self, pos: int, length: int) -> NoReturn:
# image data
if "bbox" in self.im_info:
tile = [ImageFile._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 = [ImageFile._Tile("zip", (0, 0, *self.im_size), pos, self.im_rawmode)]
self.im_tile = tile
self.im_idat = length
msg = "image data found"
raise EOFError(msg)
def chunk_IEND(self, pos: int, length: int) -> NoReturn:
msg = "end of PNG image"
raise EOFError(msg)
def chunk_PLTE(self, pos: int, length: int) -> bytes:
# palette
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if self.im_mode == "P":
self.im_palette = "RGB", s
return s
def chunk_tRNS(self, pos: int, length: int) -> bytes:
# transparency
assert self.fp is not None
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;16", "RGB"):
# 2 bytes for greyscale, 6 for truecolour
if length < (6 if self.im_mode == "RGB" else 2):
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated tRNS chunk"
raise ValueError(msg)
if self.im_mode == "1":
self.im_info["transparency"] = 255 if i16(s) else 0
elif self.im_mode in ("L", "I;16"):
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: int, length: int) -> bytes:
# gamma setting
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 4:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated gAMA chunk"
raise ValueError(msg)
self.im_info["gamma"] = i32(s) / 100000.0
return s
def chunk_cHRM(self, pos: int, length: int) -> bytes:
# chromaticity, 8 unsigned ints, actual value is scaled by 100,000
# WP x,y, Red x,y, Green x,y Blue x,y
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 32:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated cHRM chunk"
raise ValueError(msg)
raw_vals = struct.unpack(">8I", s[:32])
self.im_info["chromaticity"] = tuple(elt / 100000.0 for elt in raw_vals)
return s
def chunk_sRGB(self, pos: int, length: int) -> bytes:
# srgb rendering intent, 1 byte
# 0 perceptual
# 1 relative colorimetric
# 2 saturation
# 3 absolute colorimetric
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 1:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated sRGB chunk"
raise ValueError(msg)
self.im_info["srgb"] = s[0]
return s
def chunk_pHYs(self, pos: int, length: int) -> bytes:
# pixels per unit
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 9:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "Truncated pHYs chunk"
raise ValueError(msg)
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
def chunk_tEXt(self, pos: int, length: int) -> bytes:
# text
assert self.fp is not None
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_str = k.decode("latin-1", "strict")
v_str = v.decode("latin-1", "replace")
self.im_info[k_str] = v if k == b"exif" else v_str
self.im_text[k_str] = v_str
self.check_text_memory(len(v_str))
return s
def chunk_zTXt(self, pos: int, length: int) -> bytes:
# compressed text
assert self.fp is not None
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:
msg = f"Unknown compression method {comp_method} in zTXt chunk"
raise SyntaxError(msg)
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_str = k.decode("latin-1", "strict")
v_str = v.decode("latin-1", "replace")
self.im_info[k_str] = self.im_text[k_str] = v_str
self.check_text_memory(len(v_str))
return s
def chunk_iTXt(self, pos: int, length: int) -> bytes:
# international text
assert self.fp is not None
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
if k == b"XML:com.adobe.xmp":
self.im_info["xmp"] = v
try:
k_str = k.decode("latin-1", "strict")
lang_str = lang.decode("utf-8", "strict")
tk_str = tk.decode("utf-8", "strict")
v_str = v.decode("utf-8", "strict")
except UnicodeError:
return s
self.im_info[k_str] = self.im_text[k_str] = iTXt(v_str, lang_str, tk_str)
self.check_text_memory(len(v_str))
return s
def chunk_eXIf(self, pos: int, length: int) -> bytes:
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
self.im_info["exif"] = b"Exif\x00\x00" + s
return s
# APNG chunks
def chunk_acTL(self, pos: int, length: int) -> bytes:
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 8:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "APNG contains truncated acTL chunk"
raise ValueError(msg)
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
def chunk_fcTL(self, pos: int, length: int) -> bytes:
assert self.fp is not None
s = ImageFile._safe_read(self.fp, length)
if length < 26:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
msg = "APNG contains truncated fcTL chunk"
raise ValueError(msg)
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
):
msg = "APNG contains frame sequence errors"
raise SyntaxError(msg)
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:
msg = "APNG contains invalid frames"
raise SyntaxError(msg)
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
def chunk_fdAT(self, pos: int, length: int) -> bytes:
assert self.fp is not None
if length < 4:
if ImageFile.LOAD_TRUNCATED_IMAGES:
s = ImageFile._safe_read(self.fp, length)
return s
msg = "APNG contains truncated fDAT chunk"
raise ValueError(msg)
s = ImageFile._safe_read(self.fp, 4)
seq = i32(s)
if self._seq_num != seq - 1:
msg = "APNG contains frame sequence errors"
raise SyntaxError(msg)
self._seq_num = seq
return self.chunk_IDAT(pos + 4, length - 4)
# --------------------------------------------------------------------
# PNG reader
def _accept(prefix: bytes) -> bool:
return prefix.startswith(_MAGIC)
##
# Image plugin for PNG images.
class PngImageFile(ImageFile.ImageFile):
format = "PNG"
format_description = "Portable network graphics"
def _open(self) -> None:
assert self.fp is not None
if not _accept(self.fp.read(8)):
msg = "not a PNG file"
raise SyntaxError(msg)
self._fp = self.fp
self.__frame = 0
#
# Parse headers up to the first IDAT or fDAT chunk
self.private_chunks: list[tuple[bytes, bytes] | tuple[bytes, bytes, bool]] = []
self.png: PngStream | None = 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: dict[str, str | iTXt] | None = 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) -> dict[str, str | iTXt]:
# 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)
assert self._text is not None
return self._text
def verify(self) -> None:
"""Verify PNG file"""
if self.fp is None:
msg = "verify must be called directly after open"
raise RuntimeError(msg)
# back up to beginning of IDAT block
self.fp.seek(self.tile[0][2] - 8)
assert self.png is not None
self.png.verify()
self.png.close()
super().verify()
def seek(self, frame: int) -> None:
if not self._seek_check(frame):
return
if frame < self.__frame:
self._seek(0, True)
last_frame = self.__frame
try:
for f in range(self.__frame + 1, frame + 1):
self._seek(f)
except EOFError as e:
self.seek(last_frame)
msg = "no more images in APNG file"
raise EOFError(msg) from e
def _seek(self, frame: int, rewind: bool = False) -> None:
assert self.png is not None
if isinstance(self._fp, DeferredError):
raise self._fp.ex
self.dispose: _imaging.ImagingCore | None
dispose_extent = None
if frame == 0:
if rewind:
self._fp.seek(self.__rewind)
self.png.rewind()
self.__prepare_idat = self.__rewind_idat
self._im = 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")
dispose_extent = self.info.get("bbox")
self.__frame = 0
else:
if frame != self.__frame + 1:
msg = f"cannot seek to frame {frame}"
raise ValueError(msg)
# 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":
msg = "No more images in APNG file"
raise EOFError(msg)
if cid == b"fcTL":
if frame_start:
# there must be at least one fdAT chunk between fcTL chunks
msg = "APNG missing frame data"
raise SyntaxError(msg)
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")
dispose_extent = self.info.get("bbox")
if not self.tile:
msg = "image not found in APNG frame"
raise EOFError(msg)
if dispose_extent:
self.dispose_extent: tuple[float, float, float, float] = dispose_extent
# setup frame disposal (actual disposal done when needed in the next _seek())
if self._prev_im is None and self.dispose_op == Disposal.OP_PREVIOUS:
self.dispose_op = Disposal.OP_BACKGROUND
self.dispose = None
if self.dispose_op == Disposal.OP_PREVIOUS:
if self._prev_im:
self.dispose = self._prev_im.copy()
self.dispose = self._crop(self.dispose, self.dispose_extent)
elif self.dispose_op == Disposal.OP_BACKGROUND:
self.dispose = Image.core.fill(self.mode, self.size)