#
# The Python Imaging Library
# $Id$
#
# JPEG2000 file handling
#
# History:
# 2014-03-12 ajh Created
# 2021-06-30 rogermb Extract dpi information from the 'resc' header box
#
# Copyright (c) 2014 Coriolis Systems Limited
# Copyright (c) 2014 Alastair Houghton
#
# See the README file for information on usage and redistribution.
#
import io
import os
import struct
from . import Image, ImageFile
[docs]class BoxReader:
"""
A small helper class to read fields stored in JPEG2000 header boxes
and to easily step into and read sub-boxes.
"""
def __init__(self, fp, length=-1):
self.fp = fp
self.has_length = length >= 0
self.length = length
self.remaining_in_box = -1
def _can_read(self, num_bytes):
if self.has_length and self.fp.tell() + num_bytes > self.length:
# Outside box: ensure we don't read past the known file length
return False
if self.remaining_in_box >= 0:
# Inside box contents: ensure read does not go past box boundaries
return num_bytes <= self.remaining_in_box
else:
return True # No length known, just read
def _read_bytes(self, num_bytes):
if not self._can_read(num_bytes):
msg = "Not enough data in header"
raise SyntaxError(msg)
data = self.fp.read(num_bytes)
if len(data) < num_bytes:
msg = f"Expected to read {num_bytes} bytes but only got {len(data)}."
raise OSError(msg)
if self.remaining_in_box > 0:
self.remaining_in_box -= num_bytes
return data
[docs] def read_fields(self, field_format):
size = struct.calcsize(field_format)
data = self._read_bytes(size)
return struct.unpack(field_format, data)
[docs] def read_boxes(self):
size = self.remaining_in_box
data = self._read_bytes(size)
return BoxReader(io.BytesIO(data), size)
[docs] def has_next_box(self):
if self.has_length:
return self.fp.tell() + self.remaining_in_box < self.length
else:
return True
[docs] def next_box_type(self):
# Skip the rest of the box if it has not been read
if self.remaining_in_box > 0:
self.fp.seek(self.remaining_in_box, os.SEEK_CUR)
self.remaining_in_box = -1
# Read the length and type of the next box
lbox, tbox = self.read_fields(">I4s")
if lbox == 1:
lbox = self.read_fields(">Q")[0]
hlen = 16
else:
hlen = 8
if lbox < hlen or not self._can_read(lbox - hlen):
msg = "Invalid header length"
raise SyntaxError(msg)
self.remaining_in_box = lbox - hlen
return tbox
def _parse_codestream(fp):
"""Parse the JPEG 2000 codestream to extract the size and component
count from the SIZ marker segment, returning a PIL (size, mode) tuple."""
hdr = fp.read(2)
lsiz = struct.unpack(">H", hdr)[0]
siz = hdr + fp.read(lsiz - 2)
lsiz, rsiz, xsiz, ysiz, xosiz, yosiz, _, _, _, _, csiz = struct.unpack_from(
">HHIIIIIIIIH", siz
)
ssiz = [None] * csiz
xrsiz = [None] * csiz
yrsiz = [None] * csiz
for i in range(csiz):
ssiz[i], xrsiz[i], yrsiz[i] = struct.unpack_from(">BBB", siz, 36 + 3 * i)
size = (xsiz - xosiz, ysiz - yosiz)
if csiz == 1:
if (yrsiz[0] & 0x7F) > 8:
mode = "I;16"
else:
mode = "L"
elif csiz == 2:
mode = "LA"
elif csiz == 3:
mode = "RGB"
elif csiz == 4:
mode = "RGBA"
else:
mode = None
return size, mode
def _res_to_dpi(num, denom, exp):
"""Convert JPEG2000's (numerator, denominator, exponent-base-10) resolution,
calculated as (num / denom) * 10^exp and stored in dots per meter,
to floating-point dots per inch."""
if denom != 0:
return (254 * num * (10**exp)) / (10000 * denom)
def _parse_jp2_header(fp):
"""Parse the JP2 header box to extract size, component count,
color space information, and optionally DPI information,
returning a (size, mode, mimetype, dpi) tuple."""
# Find the JP2 header box
reader = BoxReader(fp)
header = None
mimetype = None
while reader.has_next_box():
tbox = reader.next_box_type()
if tbox == b"jp2h":
header = reader.read_boxes()
break
elif tbox == b"ftyp":
if reader.read_fields(">4s")[0] == b"jpx ":
mimetype = "image/jpx"
size = None
mode = None
bpc = None
nc = None
dpi = None # 2-tuple of DPI info, or None
while header.has_next_box():
tbox = header.next_box_type()
if tbox == b"ihdr":
height, width, nc, bpc = header.read_fields(">IIHB")
size = (width, height)
if nc == 1 and (bpc & 0x7F) > 8:
mode = "I;16"
elif nc == 1:
mode = "L"
elif nc == 2:
mode = "LA"
elif nc == 3:
mode = "RGB"
elif nc == 4:
mode = "RGBA"
elif tbox == b"res ":
res = header.read_boxes()
while res.has_next_box():
tres = res.next_box_type()
if tres == b"resc":
vrcn, vrcd, hrcn, hrcd, vrce, hrce = res.read_fields(">HHHHBB")
hres = _res_to_dpi(hrcn, hrcd, hrce)
vres = _res_to_dpi(vrcn, vrcd, vrce)
if hres is not None and vres is not None:
dpi = (hres, vres)
break
if size is None or mode is None:
msg = "Malformed JP2 header"
raise SyntaxError(msg)
return size, mode, mimetype, dpi
##
# Image plugin for JPEG2000 images.
[docs]class Jpeg2KImageFile(ImageFile.ImageFile):
format = "JPEG2000"
format_description = "JPEG 2000 (ISO 15444)"
def _open(self):
sig = self.fp.read(4)
if sig == b"\xff\x4f\xff\x51":
self.codec = "j2k"
self._size, self.mode = _parse_codestream(self.fp)
else:
sig = sig + self.fp.read(8)
if sig == b"\x00\x00\x00\x0cjP \x0d\x0a\x87\x0a":
self.codec = "jp2"
header = _parse_jp2_header(self.fp)
self._size, self.mode, self.custom_mimetype, dpi = header
if dpi is not None:
self.info["dpi"] = dpi
else:
msg = "not a JPEG 2000 file"
raise SyntaxError(msg)
if self.size is None or self.mode is None:
msg = "unable to determine size/mode"
raise SyntaxError(msg)
self._reduce = 0
self.layers = 0
fd = -1
length = -1
try:
fd = self.fp.fileno()
length = os.fstat(fd).st_size
except Exception:
fd = -1
try:
pos = self.fp.tell()
self.fp.seek(0, io.SEEK_END)
length = self.fp.tell()
self.fp.seek(pos)
except Exception:
length = -1
self.tile = [
(
"jpeg2k",
(0, 0) + self.size,
0,
(self.codec, self._reduce, self.layers, fd, length),
)
]
@property
def reduce(self):
# https://github.com/python-pillow/Pillow/issues/4343 found that the
# new Image 'reduce' method was shadowed by this plugin's 'reduce'
# property. This attempts to allow for both scenarios
return self._reduce or super().reduce
@reduce.setter
def reduce(self, value):
self._reduce = value
[docs] def load(self):
if self.tile and self._reduce:
power = 1 << self._reduce
adjust = power >> 1
self._size = (
int((self.size[0] + adjust) / power),
int((self.size[1] + adjust) / power),
)
# Update the reduce and layers settings
t = self.tile[0]
t3 = (t[3][0], self._reduce, self.layers, t[3][3], t[3][4])
self.tile = [(t[0], (0, 0) + self.size, t[2], t3)]
return ImageFile.ImageFile.load(self)
def _accept(prefix):
return (
prefix[:4] == b"\xff\x4f\xff\x51"
or prefix[:12] == b"\x00\x00\x00\x0cjP \x0d\x0a\x87\x0a"
)
# ------------------------------------------------------------
# Save support
def _save(im, fp, filename):
# Get the keyword arguments
info = im.encoderinfo
if filename.endswith(".j2k") or info.get("no_jp2", False):
kind = "j2k"
else:
kind = "jp2"
offset = info.get("offset", None)
tile_offset = info.get("tile_offset", None)
tile_size = info.get("tile_size", None)
quality_mode = info.get("quality_mode", "rates")
quality_layers = info.get("quality_layers", None)
if quality_layers is not None and not (
isinstance(quality_layers, (list, tuple))
and all(
[
isinstance(quality_layer, (int, float))
for quality_layer in quality_layers
]
)
):
msg = "quality_layers must be a sequence of numbers"
raise ValueError(msg)
num_resolutions = info.get("num_resolutions", 0)
cblk_size = info.get("codeblock_size", None)
precinct_size = info.get("precinct_size", None)
irreversible = info.get("irreversible", False)
progression = info.get("progression", "LRCP")
cinema_mode = info.get("cinema_mode", "no")
mct = info.get("mct", 0)
signed = info.get("signed", False)
fd = -1
if hasattr(fp, "fileno"):
try:
fd = fp.fileno()
except Exception:
fd = -1
im.encoderconfig = (
offset,
tile_offset,
tile_size,
quality_mode,
quality_layers,
num_resolutions,
cblk_size,
precinct_size,
irreversible,
progression,
cinema_mode,
mct,
signed,
fd,
)
ImageFile._save(im, fp, [("jpeg2k", (0, 0) + im.size, 0, kind)])
# ------------------------------------------------------------
# Registry stuff
Image.register_open(Jpeg2KImageFile.format, Jpeg2KImageFile, _accept)
Image.register_save(Jpeg2KImageFile.format, _save)
Image.register_extensions(
Jpeg2KImageFile.format, [".jp2", ".j2k", ".jpc", ".jpf", ".jpx", ".j2c"]
)
Image.register_mime(Jpeg2KImageFile.format, "image/jp2")