Function to_rgba

lib/matplotlib/colors.py:306–350

Convert *c* to an RGBA color. Parameters ---------- c : :mpltype:`color` or ``np.ma.masked`` alpha : float, optional If *alpha* is given, force the alpha value of the returned RGBA tuple to *alpha*. If None, the alpha value from *c* is used. If *c* doe

(c, alpha=None)

def to_rgba(c, alpha=None):
    """
    Convert *c* to an RGBA color.

    Parameters
    ----------
    c : :mpltype:`color` or ``np.ma.masked``

    alpha : float, optional
        If *alpha* is given, force the alpha value of the returned RGBA tuple
        to *alpha*.

        If None, the alpha value from *c* is used. If *c* does not have an
        alpha channel, then alpha defaults to 1.

        *alpha* is ignored for the color value ``"none"`` (case-insensitive),
        which always maps to ``(0, 0, 0, 0)``.

    Returns
    -------
    tuple
        Tuple of floats ``(r, g, b, a)``, where each channel (red, green, blue,
        alpha) can assume values between 0 and 1.
    """
    if isinstance(c, tuple) and len(c) == 2:
        if alpha is None:
            c, alpha = c
        else:
            c = c[0]
    # Special-case nth color syntax because it should not be cached.
    if _is_nth_color(c):
        prop_cycler = mpl.rcParams['axes.prop_cycle']
        colors = prop_cycler.by_key().get('color', ['k'])
        c = colors[int(c[1:]) % len(colors)]
    try:
        rgba = _colors_full_map.cache[c, alpha]
    except (KeyError, TypeError):  # Not in cache, or unhashable.
        rgba = None
    if rgba is None:  # Suppress exception chaining of cache lookup failure.
        rgba = _to_rgba_no_colorcycle(c, alpha)
        try:
            _colors_full_map.cache[c, alpha] = rgba
        except TypeError:
            pass
    return rgba


def _to_rgba_no_colorcycle(c, alpha=None):