# 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

    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

        def read_fields(self, field_format):
            size = struct.calcsize(field_format)
            data = self._read_bytes(size)
            return struct.unpack(field_format, data)

        def read_boxes(self):
            size = self.remaining_in_box
            data = self._read_bytes(size)
            return BoxReader(io.BytesIO(data), size)

        def has_next_box(self):
            if self.has_length:
                return self.fp.tell() + self.remaining_in_box < self.length
            else:
                return True

        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.

    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

        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")