# Source code for PIL.GribStubImagePlugin

    #
    # The Python Imaging Library
    # $Id$
    #
    # GRIB stub adapter
    #
    # Copyright (c) 1996-2003 by Fredrik Lundh
    #
    # See the README file for information on usage and redistribution.
    #
    from __future__ import annotations

    from . import Image, ImageFile

    _handler = None

    def register_handler(handler):
        """
        Install application-specific GRIB image handler.

        :param handler: Handler object.
        """
        global _handler
        _handler = handler

    # --------------------------------------------------------------------
    # Image adapter

    def _accept(prefix):
        return prefix[:4] == b"GRIB" and prefix[7] == 1

    class GribStubImageFile(ImageFile.StubImageFile):
        format = "GRIB"
        format_description = "GRIB"

        def _open(self):
            offset = self.fp.tell()

            if not _accept(self.fp.read(8)):
                msg = "Not a GRIB file"
                raise SyntaxError(msg)

            self.fp.seek(offset)

            # make something up
            self._mode = "F"
            self._size = 1, 1

            loader = self._load()
            if loader:
                loader.open(self)

        def _load(self):
            return _handler

    def _save(im, fp, filename):
        if _handler is None or not hasattr(_handler, "save"):
            msg = "GRIB save handler not installed"
            raise OSError(msg)
        _handler.save(im, fp, filename)

    # --------------------------------------------------------------------
    # Registry

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

    Image.register_extension(GribStubImageFile.format, ".grib")