# 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 . import Image, ImageFile

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

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

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

    def _accept(prefix):
        return prefix[0:1] == b"P" and prefix[1] in b"0456y"

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

    class PpmImageFile(ImageFile.ImageFile):

        format = "PPM"
        format_description = "Pbmplus image"

        def _token(self, s=b""):
            while True:  # read until next whitespace
                c = self.fp.read(1)
                if not c or c in b_whitespace:
                    break
                if c > b"\x79":
                    raise ValueError("Expected ASCII value, found binary")
                s = s + c
                if len(s) > 9:
                    raise ValueError("Expected int, got > 9 digits")
            return s

        def _open(self):

            # check magic
            s = self.fp.read(1)
            if s != b"P":
                raise SyntaxError("not a PPM file")
            magic_number = self._token(s)
            mode = MODES[magic_number]

            self.custom_mimetype = {
                b"P4": "image/x-portable-bitmap",
                b"P5": "image/x-portable-graymap",
                b"P6": "image/x-portable-pixmap",
            }.get(magic_number)

            if mode == "1":
                self.mode = "1"
                rawmode = "1;I"
            else:
                self.mode = rawmode = mode

            for ix in range(3):
                while True:
                    while True:
                        s = self.fp.read(1)
                        if s not in b_whitespace:
                            break
                        if s == b"":
                            raise ValueError("File does not extend beyond magic number")
                    if s != b"#":
                        break
                    s = self.fp.readline()
                s = int(self._token(s))
                if ix == 0:
                    xsize = s
                elif ix == 1:
                    ysize = s
                    if mode == "1":
                        break
                elif ix == 2:
                    # maxgrey
                    if s > 255:
                        if not mode == "L":
                            raise ValueError(f"Too many colors for band: {s}")
                        if s < 2 ** 16:
                            self.mode = "I"
                            rawmode = "I;16B"
                        else:
                            self.mode = "I"
                            rawmode = "I;32B"

            self._size = xsize, ysize
            self.tile = [("raw", (0, 0, xsize, ysize), self.fp.tell(), (rawmode, 0, 1))]

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

    def _save(im, fp, filename):
        if im.mode == "1":
            rawmode, head = "1;I", b"P4"
        elif im.mode == "L":
            rawmode, head = "L", b"P5"
        elif im.mode == "I":
            if im.getextrema()[1] < 2 ** 16:
                rawmode, head = "I;16B", b"P5"
            else:
                rawmode, head = "I;32B", b"P5"
        elif im.mode == "RGB":
            rawmode, head = "RGB", b"P6"
        elif im.mode == "RGBA":
            rawmode, head = "RGB", b"P6"
        else:
            raise OSError(f"cannot write mode {im.mode} as PPM")
        fp.write(head + ("\n%d %d\n" % im.size).encode("ascii"))
        if head == b"P6":
            fp.write(b"255\n")
        if head == b"P5":
            if rawmode == "L":
                fp.write(b"255\n")
            elif rawmode == "I;16B":
                fp.write(b"65535\n")
            elif rawmode == "I;32B":
                fp.write(b"2147483648\n")
        ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, 1))])

        # ALTERNATIVE: save via builtin debug function
        # im._dump(filename)

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

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

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

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