Function check_palette

_plotly_utils/png.py:242–274

Check a palette argument (to the :class:`Writer` class) for validity. Returns the palette as a list if okay; raises an exception otherwise.

(palette)

def check_palette(palette):
    """
    Check a palette argument (to the :class:`Writer` class) for validity.
    Returns the palette as a list if okay;
    raises an exception otherwise.
    """

    # None is the default and is allowed.
    if palette is None:
        return None

    p = list(palette)
    if not (0 < len(p) <= 256):
        raise ProtocolError(
            "a palette must have between 1 and 256 entries,"
            " see https://www.w3.org/TR/PNG/#11PLTE"
        )
    seen_triple = False
    for i, t in enumerate(p):
        if len(t) not in (3, 4):
            raise ProtocolError("palette entry %d: entries must be 3- or 4-tuples." % i)
        if len(t) == 3:
            seen_triple = True
        if seen_triple and len(t) == 4:
            raise ProtocolError(
                "palette entry %d: all 4-tuples must precede all 3-tuples" % i
            )
        for x in t:
            if int(x) != x or not (0 <= x <= 255):
                raise ProtocolError(
                    "palette entry %d: values must be integer: 0 <= x <= 255" % i
                )
    return p


def check_sizes(size, width, height):