# Source code for PIL.ImagePalette

    #
    # The Python Imaging Library.
    # $Id$
    #
    # image palette object
    #
    # History:
    # 1996-03-11 fl   Rewritten.
    # 1997-01-03 fl   Up and running.
    # 1997-08-23 fl   Added load hack
    # 2001-04-16 fl   Fixed randint shadow bug in random()
    #
    # Copyright (c) 1997-2001 by Secret Labs AB
    # Copyright (c) 1996-1997 by Fredrik Lundh
    #
    # See the README file for information on usage and redistribution.
    #

    import array
    import warnings

    from . import GimpGradientFile, GimpPaletteFile, ImageColor, PaletteFile

    class ImagePalette:
        """
        Color palette for palette mapped images

        :param mode: The mode to use for the palette. See:
            :ref:`concept-modes`. Defaults to "RGB"
        :param palette: An optional palette. If given, it must be a bytearray,
            an array or a list of ints between 0-255. The list must consist of
            all channels for one color followed by the next color (e.g. RGBRGBRGB).
            Defaults to an empty palette.
        :param size: An optional palette size. If given, an error is raised
            if ``palette`` is not of equal length.
        """

        def __init__(self, mode="RGB", palette=None, size=0):
            self.mode = mode
            self.rawmode = None  # if set, palette contains raw data
            self.palette = palette or bytearray()
            self.dirty = None
            if size != 0:
                warnings.warn(
                    "The size parameter is deprecated and will be removed in Pillow 10 "
                    "(2023-07-01).",
                    DeprecationWarning,
                )
                if size != len(self.palette):
                    raise ValueError("wrong palette size")

        @property
        def palette(self):
            return self._palette

        @palette.setter
        def palette(self, palette):
            self._palette = palette

            mode_len = len(self.mode)
            self.colors = {}
            for i in range(0, len(self.palette), mode_len):
                color = tuple(self.palette[i : i + mode_len])
                if color in self.colors:
                    continue
                self.colors[color] = i // mode_len

        def copy(self):
            new = ImagePalette()

            new.mode = self.mode
            new.rawmode = self.rawmode
            if self.palette is not None:
                new.palette = self.palette[:]
            new.dirty = self.dirty

            return new

        def getdata(self):
            """
            Get palette contents in format suitable for the low-level
            ``im.putpalette`` primitive.

            .. warning:: This method is experimental.
            """
            if self.rawmode:
                return self.rawmode, self.palette
            return self.mode, self.tobytes()

        def tobytes(self):
            """Convert palette to bytes.

            .. warning:: This method is experimental.
            """
            if self.rawmode:
                raise ValueError("palette contains raw palette data")
            if isinstance(self.palette, bytes):
                return self.palette
            arr = array.array("B", self.palette)
            return arr.tobytes()

        # Declare tostring as an alias for tobytes
        tostring = tobytes

        def getcolor(self, color, image=None):
            """Given an rgb tuple, allocate palette entry.

            .. warning:: This method is experimental.
            """
            if self.rawmode:
                raise ValueError("palette contains raw palette data")
            if isinstance(color, tuple):
                if self.mode == "RGB":
                    if len(color) == 4 and color[3] == 255:
                        color = color[:3]
                elif self.mode == "RGBA":
                    if len(color) == 3:
                        color += (255,)
                try:
                    return self.colors[color]
                except KeyError as e:
                    # allocate new color slot
                    if not isinstance(self.palette, bytearray):
                        self._palette = bytearray(self.palette)
                    index = len(self.palette) // 3
                    special_colors = ()
                    if image:
                        special_colors = (
                            image.info.get("background"),
                            image.info.get("transparency"),
                        )
                    while index in special_colors:
                        index += 1
                    if index >= 256:
                        if image:
                            # Search for an unused index
                            for i, count in reversed(list(enumerate(image.histogram()))):
                                if count == 0 and i not in special_colors:
                                    index = i
                                    break
                        if index >= 256:
                            raise ValueError("cannot allocate more than 256 colors") from e
                    self.colors[color] = index
                    if index * 3 < len(self.palette):
                        self._palette = (
                            self.palette[: index * 3]
                            + bytes(color)
                            + self.palette[index * 3 + 3 :]
                        )
                    else:
                        self._palette += bytes(color)
                    self.dirty = 1
                    return index
            else:
                raise ValueError(f"unknown color specifier: {repr(color)}")

        def save(self, fp):
            """Save palette to text file.

            .. warning:: This method is experimental.
            """
            if self.rawmode:
                raise ValueError("palette contains raw palette data")
            if isinstance(fp, str):
                fp = open(fp, "w")
            fp.write("# Palette\n")
            fp.write(f"# Mode: {self.mode}\n")
            for i in range(256):
                fp.write(f"{i}")
                for j in range(i * len(self.mode), (i + 1) * len(self.mode)):
                    try:
                        fp.write(f" {self.palette[j]}")
                    except IndexError:
                        fp.write(" 0")
                fp.write("\n")
            fp.close()

    # --------------------------------------------------------------------
    # Internal

    def raw(rawmode, data):
        palette = ImagePalette()
        palette.rawmode = rawmode
        palette.palette = data
        palette.dirty = 1
        return palette

    # --------------------------------------------------------------------
    # Factories

    def make_linear_lut(black, white):
        lut = []
        if black == 0:
            for i in range(256):
                lut.append(white * i // 255)
        else:
            raise NotImplementedError  # FIXME
        return lut

    def make_gamma_lut(exp):
        lut = []
        for i in range(256):
            lut.append(int(((i / 255.0) ** exp) * 255.0 + 0.5))
        return lut

    def negative(mode="RGB"):
        palette = list(range(256 * len(mode)))
        palette.reverse()
        return ImagePalette(mode, [i // len(mode) for i in palette])

    def random(mode="RGB"):
        from random import randint

        palette = []
        for i in range(256 * len(mode)):
            palette.append(randint(0, 255))
        return ImagePalette(mode, palette)

    def sepia(white="#fff0c0"):
        bands = [make_linear_lut(0, band) for band in ImageColor.getrgb(white)]
        return ImagePalette("RGB", [bands[i % 3][i // 3] for i in range(256 * 3)])

    def wedge(mode="RGB"):
        palette = list(range(256 * len(mode)))
        return ImagePalette(mode, [i // len(mode) for i in palette])

    def load(filename):

        # FIXME: supports GIMP gradients only

        with open(filename, "rb") as fp:

            for paletteHandler in [
                GimpPaletteFile.GimpPaletteFile,
                GimpGradientFile.GimpGradientFile,
                PaletteFile.PaletteFile,
            ]:
                try:
                    fp.seek(0)
                    lut = paletteHandler(fp).getpalette()
                    if lut:
                        break
                except (SyntaxError, ValueError):
                    # import traceback
                    # traceback.print_exc()
                    pass
            else:
                raise OSError("cannot load palette")

        return lut  # data, rawmode