Source code for PIL.Jpeg2KImagePlugin

#
# 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): raise SyntaxError("Not enough data in header") data = self.fp.read(num_bytes) if len(data) < num_bytes: raise OSError( f"Expected to read {num_bytes} bytes but only got {len(data)}." ) 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): raise SyntaxError("Invalid header length") 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: raise SyntaxError("Malformed JP2 header") 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: raise SyntaxError("not a JPEG 2000 file") if self.size is None or self.mode is None: raise SyntaxError("unable to determine size/mode") 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): if filename.endswith(".j2k"): kind = "j2k" else: kind = "jp2" # Get the keyword arguments info = im.encoderinfo 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 ] ) ): raise ValueError("quality_layers must be a sequence of numbers") 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") 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, 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")