Function to_rgba_array

lib/matplotlib/colors.py:438–543

Convert *c* to a (n, 4) array of RGBA colors. Parameters ---------- c : :mpltype:`color` or list of :mpltype:`color` or RGB(A) array If *c* is a masked array, an `~numpy.ndarray` is returned with a (0, 0, 0, 0) row for each masked value or row in *c*. alpha : f

(c, alpha=None)

def to_rgba_array(c, alpha=None):
    """
    Convert *c* to a (n, 4) array of RGBA colors.

    Parameters
    ----------
    c : :mpltype:`color` or list of :mpltype:`color` or RGB(A) array
        If *c* is a masked array, an `~numpy.ndarray` is returned with a
        (0, 0, 0, 0) row for each masked value or row in *c*.

    alpha : float or sequence of floats, 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)``.

        If *alpha* is a sequence and *c* is a single color, *c* will be
        repeated to match the length of *alpha*.

    Returns
    -------
    array
        (n, 4) array of RGBA colors,  where each channel (red, green, blue,
        alpha) can assume values between 0 and 1.
    """
    if isinstance(c, tuple) and len(c) == 2 and isinstance(c[1], Real):
        if alpha is None:
            c, alpha = c
        else:
            c = c[0]
    # Special-case inputs that are already arrays, for performance.  (If the
    # array has the wrong kind or shape, raise the error during one-at-a-time
    # conversion.)
    if np.iterable(alpha):
        alpha = np.asarray(alpha).ravel()
    if (isinstance(c, np.ndarray) and c.dtype.kind in "if"
            and c.ndim == 2 and c.shape[1] in [3, 4]):
        mask = c.mask.any(axis=1) if np.ma.is_masked(c) else None
        c = np.ma.getdata(c)
        if np.iterable(alpha):
            if c.shape[0] == 1 and alpha.shape[0] > 1:
                c = np.tile(c, (alpha.shape[0], 1))
            elif c.shape[0] != alpha.shape[0]:
                raise ValueError("The number of colors must match the number"
                                 " of alpha values if there are more than one"
                                 " of each.")
        if c.shape[1] == 3:
            result = np.column_stack([c, np.zeros(len(c))])
            result[:, -1] = alpha if alpha is not None else 1.
        elif c.shape[1] == 4:
            result = c.copy()
            if alpha is not None:
                result[:, -1] = alpha
        if mask is not None: