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# Source code for PIL.PpmImagePlugin

    #
    # The Python Imaging Library.
    # $Id$
    #
    # PPM support for PIL
    #
    # History:
    #       96-03-24 fl     Created
    #       98-03-06 fl     Write RGBA images (as RGB, that is)
    #
    # Copyright (c) Secret Labs AB 1997-98.
    # Copyright (c) Fredrik Lundh 1996.
    #
    # See the README file for information on usage and redistribution.
    #
    from __future__ import annotations

    import math
    from typing import IO

    from . import Image, ImageFile
    from ._binary import i16be as i16
    from ._binary import o8
    from ._binary import o32le as o32

    #
    # --------------------------------------------------------------------

    b_whitespace = b"\x20\x09\x0a\x0b\x0c\x0d"

    MODES = {
        # standard
        b"P1": "1",
        b"P2": "L",
        b"P3": "RGB",
        b"P4": "1",
        b"P5": "L",
        b"P6": "RGB",
        # extensions
        b"P0CMYK": "CMYK",
        b"Pf": "F",
        # PIL extensions (for test purposes only)
        b"PyP": "P",
        b"PyRGBA": "RGBA",
        b"PyCMYK": "CMYK",
    }

    def _accept(prefix: bytes) -> bool:
        return prefix.startswith(b"P") and prefix[1] in b"0123456fy"

    ##
    # Image plugin for PBM, PGM, and PPM images.

    class PpmImageFile(ImageFile.ImageFile):
        format = "PPM"
        format_description = "Pbmplus image"

        def _read_magic(self) -> bytes:
            assert self.fp is not None

            magic = b""
            # read until whitespace or longest available magic number
            for _ in range(6):
                c = self.fp.read(1)
                if not c or c in b_whitespace:
                    break
                magic += c
            return magic

        def _read_token(self) -> bytes:
            assert self.fp is not None

            token = b""
            while len(token) <= 10:  # read until next whitespace or limit of 10 characters
                c = self.fp.read(1)
                if not c:
                    break
                elif c in b_whitespace:  # token ended
                    if not token:
                        # skip whitespace at start
                        continue
                    break
                elif c == b"#":
                    # ignores rest of the line; stops at CR, LF or EOF
                    while self.fp.read(1) not in b"\r\n":
                        pass
                    continue
                token += c
            if not token:
                # Token was not even 1 byte
                msg = "Reached EOF while reading header"
                raise ValueError(msg)
            elif len(token) > 10:
                msg_too_long = b"Token too long in file header: %s" % token
                raise ValueError(msg_too_long)
            return token

        def _open(self) -> None:
            assert self.fp is not None

            magic_number = self._read_magic()
            try:
                mode = MODES[magic_number]
            except KeyError:
                msg = "not a PPM file"
                raise SyntaxError(msg)
            self._mode = mode

            if magic_number in (b"P1", b"P4"):
                self.custom_mimetype = "image/x-portable-bitmap"
            elif magic_number in (b"P2", b"P5"):
                self.custom_mimetype = "image/x-portable-graymap"
            elif magic_number in (b"P3", b"P6"):
                self.custom_mimetype = "image/x-portable-pixmap"

            self._size = int(self._read_token()), int(self._read_token())

            decoder_name = "raw"
            if magic_number in (b"P1", b"P2", b"P3"):
                decoder_name = "ppm_plain"

            args: str | tuple[str | int, ...]
            if mode == "1":
                args = "1;I"
            elif mode == "F":
                scale = float(self._read_token())
                if scale == 0.0 or not math.isfinite(scale):
                    msg = "scale must be finite and non-zero"
                    raise ValueError(msg)
                self.info["scale"] = abs(scale)

                rawmode = "F;32F" if scale < 0 else "F;32BF"
                args = (rawmode, 0, -1)
            else:
                maxval = int(self._read_token())
                if not 0 < maxval < 65536:
                    msg = "maxval must be greater than 0 and less than 65536"
                    raise ValueError(msg)
                if maxval > 255 and mode == "L":
                    self._mode = "I"

                rawmode = mode
                if decoder_name != "ppm_plain":
                    # If maxval matches a bit depth, use the raw decoder directly
                    if maxval == 65535 and mode == "L":
                        rawmode = "I;16B"
                    elif maxval != 255:
                        decoder_name = "ppm"

                args = rawmode if decoder_name == "raw" else (rawmode, maxval)
            self.tile = [
                ImageFile._Tile(decoder_name, (0, 0) + self.size, self.fp.tell(), args)
            ]

    #
    # --------------------------------------------------------------------

    class PpmPlainDecoder(ImageFile.PyDecoder):
        _pulls_fd = True
        _comment_spans: bool

        def _read_block(self) -> bytes:
            assert self.fd is not None

            return self.fd.read(ImageFile.SAFEBLOCK)

        def _find_comment_end(self, block: bytes, start: int = 0) -> int:
            a = block.find(b"\n", start)
            b = block.find(b"\r", start)
            return min(a, b) if a * b > 0 else max(a, b)  # lowest nonnegative index (or -1)

        def _ignore_comments(self, block: bytes) -> bytes:
            if self._comment_spans:
                # Finish current comment
                while block:
                    comment_end = self._find_comment_end(block)
                    if comment_end != -1:
                        # Comment ends in this block
                        # Delete tail of comment
                        block = block[comment_end + 1 :]
                        break
                    else:
                        # Comment spans whole block
                        # So read the next block, looking for the end
                        block = self._read_block()

            # Search for any further comments
            self._comment_spans = False
            while True:
                comment_start = block.find(b"#")
                if comment_start == -1:
                    # No comment found
                    break
                comment_end = self._find_comment_end(block, comment_start)
                if comment_end != -1:
                    # Comment ends in this block
                    # Delete comment
                    block = block[:comment_start] + block[comment_end + 1 :]
                else:
                    # Comment continues to next block(s)
                    block = block[:comment_start]
                    self._comment_spans = True
                    break
            return block

        def _decode_bitonal(self) -> bytearray:
            """
            This is a separate method because in the plain PBM format, all data tokens are
            exactly one byte, so the inter-token whitespace is optional.
            """
            data = bytearray()
            total_bytes = self.state.xsize * self.state.ysize

            while len(data) != total_bytes:
                block = self._read_block()  # read next block
                if not block:
                    # eof
                    break

                block = self._ignore_comments(block)

                tokens = b"".join(block.split())
                for token in tokens:
                    if token not in (48, 49):
                        msg = b"Invalid token for this mode: %s" % bytes([token])
                        raise ValueError(msg)
                data = (data + tokens)[:total_bytes]
            invert = bytes.maketrans(b"01", b"\xff\x00")
            return data.translate(invert)

        def _decode_blocks(self, maxval: int) -> bytearray:
            data = bytearray()
            max_len = 10
            out_byte_count = 4 if self.mode == "I" else 1
            out_max = 65535 if self.mode == "I" else 255
            bands = Image.getmodebands(self.mode)
            total_bytes = self.state.xsize * self.state.ysize * bands * out_byte_count

            half_token = b""
            while len(data) != total_bytes:
                block = self._read_block()  # read next block
                if not block:
                    if half_token:
                        block = bytearray(b" ")  # flush half_token
                    else:
                        # eof
                        break

                block = self._ignore_comments(block)

                if half_token:
                    block = half_token + block  # stitch half_token to new block
                    half_token = b""

                tokens = block.split()

                if block and not block[-1:].isspace():  # block might split token
                    half_token = tokens.pop()  # save half token for later
                    if len(half_token) > max_len:  # prevent buildup of half_token
                        msg = (
                            b"Token too long found in data: %s" % half_token[: max_len + 1]
                        )
                        raise ValueError(msg)

                for token in tokens:
                    if len(token) > max_len:
                        msg = b"Token too long found in data: %s" % token[: max_len + 1]
                        raise ValueError(msg)
                    value = int(token)
                    if value < 0:
                        msg_str = f"Channel value is negative: {value}"
                        raise ValueError(msg_str)
                    if value > maxval:
                        msg_str = f"Channel value too large for this mode: {value}"
                        raise ValueError(msg_str)
                    value = round(value / maxval * out_max)
                    data += o32(value) if self.mode == "I" else o8(value)
                    if len(data) == total_bytes:  # finished!
                        break
            return data

        def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:
            self._comment_spans = False
            if self.mode == "1":
                data = self._decode_bitonal()
                rawmode = "1;8"
            else:
                maxval = self.args[-1]
                data = self._decode_blocks(maxval)
                rawmode = "I;32" if self.mode == "I" else self.mode
            self.set_as_raw(bytes(data), rawmode)
            return -1, 0

    class PpmDecoder(ImageFile.PyDecoder):
        _pulls_fd = True

        def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:
            assert self.fd is not None

            data = bytearray()
            maxval = self.args[-1]
            in_byte_count = 1 if maxval < 256 else 2
            out_byte_count = 4 if self.mode == "I" else 1
            out_max = 65535 if self.mode == "I" else 255
            bands = Image.getmodebands(self.mode)
            dest_length = self.state.xsize * self.state.ysize * bands * out_byte_count
            while len(data) < dest_length:
                pixels = self.fd.read(in_byte_count * bands)
                if len(pixels) < in_byte_count * bands:
                    # eof
                    break
                for b in range(bands):
                    value = (
                        pixels[b] if in_byte_count == 1 else i16(pixels, b * in_byte_count)
                    )
                    value = min(out_max, round(value / maxval * out_max))
                    data += o32(value) if self.mode == "I" else o8(value)
            rawmode = "I;32" if self.mode == "I" else self.mode
            self.set_as_raw(bytes(data), rawmode)
            return -1, 0

    #
    # --------------------------------------------------------------------

    def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
        if im.mode == "1":
            rawmode, head = "1;I", b"P4"
        elif im.mode == "L":
            rawmode, head = "L", b"P5"
        elif im.mode in ("I", "I;16"):
            rawmode, head = "I;16B", b"P5"
        elif im.mode in ("RGB", "RGBA"):
            rawmode, head = "RGB", b"P6"
        elif im.mode == "F":
            rawmode, head = "F;32F", b"Pf"
        else:
            msg = f"cannot write mode {im.mode} as PPM"
            raise OSError(msg)
        fp.write(head + b"\n%d %d\n" % im.size)
        if head == b"P6":
            fp.write(b"255\n")
        elif head == b"P5":
            if rawmode == "L":
                fp.write(b"255\n")
            else:
                fp.write(b"65535\n")
        elif head == b"Pf":
            fp.write(b"-1.0\n")
        row_order = -1 if im.mode == "F" else 1
        ImageFile._save(
            im, fp, [ImageFile._Tile("raw", (0, 0) + im.size, 0, (rawmode, 0, row_order))]
        )

    #
    # --------------------------------------------------------------------

    Image.register_open(PpmImageFile.format, PpmImageFile, _accept)
    Image.register_save(PpmImageFile.format, _save)

    Image.register_decoder("ppm", PpmDecoder)
    Image.register_decoder("ppm_plain", PpmPlainDecoder)

    Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm", ".pfm"])

    Image.register_mime(PpmImageFile.format, "image/x-portable-anymap")