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