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 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 len(c[0]) == 4):
            # 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 _has_alpha_channel_array(cseq):
    """Return whether each element in *cseq* is a color with an alpha channel"""
    if is_color_like(cseq):
        cseq = [cseq]  # force it to be a sequence
    return [_has_alpha_channel(c) for c in cseq]


 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))
    assert not mcolors._has_alpha_channel(1)  # non-colors don't have alpha channels


 def test_cn():
Original file line number	Diff line number	Diff line change
Expand Up		@@ -232,9 +232,34 @@ 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"""
Copy link Member timhoffmOct 7, 2024 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. We should mention that the result is undefined ifc is not a valid color specifier. Copy link ContributorAuthor landoskapeJan 3, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. This is now mentioned in the docstring and the comment for the final return line.
		# 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 len(c[0]) == 4):
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		# 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 _has_alpha_channel_array(cseq):
Copy link Member timhoffmOct 7, 2024 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. This is not used anywhere right now. Therefore, we don't need it here. Copy link ContributorAuthor landoskapeJan 3, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. It is now deprecated (I added the standard _api.deprecated decorator). In addition I added a deprecation file in the doc/ folder. Copy link Member timhoffmJan 4, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Um, you've just introduced this function and immediately deprecated it?!? You should simply not add it to the PR. landoskape reacted with eyes emoji
		"""Return whether each element in cseq is a color with an alpha channel"""
		if is_color_like(cseq):
		cseq = [cseq] # force it to be a sequence
		return [_has_alpha_channel(c) for c in cseq]


		def _check_color_like(**kwargs):
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -1231,10 +1231,19 @@ 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))
		assert not mcolors._has_alpha_channel(1) # non-colors don't have alpha channels
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		def test_cn():
Expand Down