Jan 6, 2025 · Nov 15, 2023 · Nov 15, 2023 · Nov 15, 2023 · Nov 21, 2023 · Jan 3, 2025
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py


 def _has_alpha_channel(c):
    """Return whether *c* is a color with an alpha channel."""
    # 4-element sequences are interpreted as r, g, b, a
    return not isinstance(c, str) and len(c) == 4
    """
    Return whether *c* is a color with an alpha channel.

    If *c* is not a valid color specifier, then the result is undefined.
    """
    # The following logic uses the assumption that c is a valid color spec.
    # For speed and simplicity, we intentionally don't care about other inputs.
    # Anything can happen with them.

    # if c is a hex, it has an alpha channel when it has 4 (or 8) digits after '#'
    if isinstance(c, str):
        if c[0] == '#' and (len(c) == 5 or len(c) == 9):
            # example: '#fff8' or '#0f0f0f80'
            return True
    else:
        # if c isn't a string, it can be an RGB(A) or a color-alpha tuple
        # if it has length 4, it has an alpha channel
        if len(c) == 4:
            # example: [0.5, 0.5, 0.5, 0.5]
            return True

        # if it has length 2, it's a color/alpha tuple
        # if the second element isn't None or the first element has length = 4
        if len(c) == 2 and (c[1] is not None or _has_alpha_channel(c[0])):
            # example: ([0.5, 0.5, 0.5, 0.5], None) or ('r', 0.5)
            return True

    # otherwise it doesn't have an alpha channel
    return False


 def _check_color_like(**kwargs):
diff --git a/lib/matplotlib/tests/test_colors.py b/lib/matplotlib/tests/test_colors.py
 def test_has_alpha_channel():
    assert mcolors._has_alpha_channel((0, 0, 0, 0))
    assert mcolors._has_alpha_channel([1, 1, 1, 1])
    assert mcolors._has_alpha_channel('#fff8')
    assert mcolors._has_alpha_channel('#0f0f0f80')
    assert mcolors._has_alpha_channel(('r', 0.5))
    assert mcolors._has_alpha_channel(([1, 1, 1, 1], None))
    assert not mcolors._has_alpha_channel('blue')  # 4-char string!
    assert not mcolors._has_alpha_channel('0.25')
    assert not mcolors._has_alpha_channel('r')
    assert not mcolors._has_alpha_channel((1, 0, 0))
    assert not mcolors._has_alpha_channel('#fff')
    assert not mcolors._has_alpha_channel('#0f0f0f')
    assert not mcolors._has_alpha_channel(('r', None))
    assert not mcolors._has_alpha_channel(([1, 1, 1], None))


 def test_cn():
Original file line number	Diff line number	Diff line change
Expand Up		@@ -232,9 +232,35 @@ def is_color_like(c):


		def _has_alpha_channel(c):
		"""Return whether c is a color with an alpha channel."""
		# 4-element sequences are interpreted as r, g, b, a
		return not isinstance(c, str) and len(c) == 4
		"""
		Return whether c is a color with an alpha channel.

		If c is not a valid color specifier, then the result is undefined.
		"""
		# The following logic uses the assumption that c is a valid color spec.
		# For speed and simplicity, we intentionally don't care about other inputs.
		# Anything can happen with them.

		# if c is a hex, it has an alpha channel when it has 4 (or 8) digits after '#'
		if isinstance(c, str):
		if c[0] == '#' and (len(c) == 5 or len(c) == 9):
		# example: '#fff8' or '#0f0f0f80'
		return True
		else:
		# if c isn't a string, it can be an RGB(A) or a color-alpha tuple
		# if it has length 4, it has an alpha channel
		if len(c) == 4:
		# example: [0.5, 0.5, 0.5, 0.5]
		return True

		# if it has length 2, it's a color/alpha tuple
		# if the second element isn't None or the first element has length = 4
		if len(c) == 2 and (c[1] is not None or _has_alpha_channel(c[0])):
		# example: ([0.5, 0.5, 0.5, 0.5], None) or ('r', 0.5)
		return True

		# otherwise it doesn't have an alpha channel
		return False


		def _check_color_like(**kwargs):
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1231,10 +1231,18 @@ def test_colormap_reversing(name):
		def test_has_alpha_channel():
		assert mcolors._has_alpha_channel((0, 0, 0, 0))
		assert mcolors._has_alpha_channel([1, 1, 1, 1])
		assert mcolors._has_alpha_channel('#fff8')
		assert mcolors._has_alpha_channel('#0f0f0f80')
		assert mcolors._has_alpha_channel(('r', 0.5))
		assert mcolors._has_alpha_channel(([1, 1, 1, 1], None))
		assert not mcolors._has_alpha_channel('blue') # 4-char string!
		assert not mcolors._has_alpha_channel('0.25')
		assert not mcolors._has_alpha_channel('r')
		assert not mcolors._has_alpha_channel((1, 0, 0))
		assert not mcolors._has_alpha_channel('#fff')
		assert not mcolors._has_alpha_channel('#0f0f0f')
		assert not mcolors._has_alpha_channel(('r', None))
		assert not mcolors._has_alpha_channel(([1, 1, 1], None))


		def test_cn():
Expand Down