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Commit08fec0d

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ENH: Add new color spec, tuple (matplotlib_color, alpha)
1 parent78bf53c commit08fec0d

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Add a new valid color format ``(matplotlib_color, alpha)``
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----------------------------------------------------------
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..plot::
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:include-source: true
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import matplotlib.pyplot as plt
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from matplotlib.patches import Rectangle
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fig, ax = plt.subplots()
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rectangle = Rectangle((.2, .2), .6, .6,
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facecolor=('blue', 0.2),
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edgecolor=('green', 0.5))
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ax.add_patch(rectangle)
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Users can define a color using the new color specification, *(matplotlib_color, alpha)*.
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Note that an explicit alpha keyword argument will override an alpha value from
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*(matplotlib_color, alpha)*.
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"""
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=================================
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Ways to set a color's alpha value
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=================================
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Compare setting alpha by the *alpha* keyword argument and by one of the Matplotlib color
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formats. Often, the *alpha* keyword is the only tool needed to add transparency to a
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color. In some cases, the *(matplotlib_color, alpha)* color format provides an easy way
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to fine-tune the appearance of a Figure.
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"""
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importmatplotlib.pyplotasplt
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importnumpyasnp
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# Fixing random state for reproducibility.
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np.random.seed(19680801)
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fig, (ax1,ax2)=plt.subplots(ncols=2,figsize=(8,4))
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x_values= [nforninrange(20)]
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y_values=np.random.randn(20)
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facecolors= ['green'ify>0else'red'foryiny_values]
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edgecolors=facecolors
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ax1.bar(x_values,y_values,color=facecolors,edgecolor=edgecolors,alpha=0.5)
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ax1.set_title("Explicit 'alpha' keyword value\nshared by all bars and edges")
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# Normalize y values to get distinct face alpha values.
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abs_y= [abs(y)foryiny_values]
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face_alphas= [n/max(abs_y)forninabs_y]
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edge_alphas= [1-alphaforalphainface_alphas]
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colors_with_alphas=list(zip(facecolors,face_alphas))
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edgecolors_with_alphas=list(zip(edgecolors,edge_alphas))
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ax2.bar(x_values,y_values,color=colors_with_alphas,
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edgecolor=edgecolors_with_alphas)
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ax2.set_title('Normalized alphas for\neach bar and each edge')
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plt.show()
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# %%
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#
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# .. admonition:: References
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#
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# The use of the following functions, methods, classes and modules is shown
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# in this example:
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#
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# - `matplotlib.axes.Axes.bar`
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# - `matplotlib.pyplot.subplots`

‎galleries/users_explain/colors/colors.py‎

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Original file line numberDiff line numberDiff line change
@@ -68,6 +68,9 @@
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| to black if cycle does not | |
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| include color. | |
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+--------------------------------------+--------------------------------------+
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| Tuple of one of the above color | - ``('green', 0.3)`` |
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| formats and an alpha float. | - ``('#f00', 0.9)`` |
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+--------------------------------------+--------------------------------------+
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.. _xkcd color survey: https://xkcd.com/color/rgb/
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‎lib/matplotlib/colors.py‎

Lines changed: 17 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -315,6 +315,13 @@ def _to_rgba_no_colorcycle(c, alpha=None):
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*alpha* is ignored for the color value ``"none"`` (case-insensitive),
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which always maps to ``(0, 0, 0, 0)``.
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"""
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ifisinstance(c,tuple)andlen(c)==2:
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ifalphaisNone:
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c,alpha=c
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else:
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c=c[0]
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ifalphaisnotNoneandnot0<=alpha<=1:
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raiseValueError("'alpha' must be between 0 and 1, inclusive")
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orig_c=c
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ifcisnp.ma.masked:
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return (0.,0.,0.,0.)
@@ -425,6 +432,11 @@ def to_rgba_array(c, alpha=None):
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(n, 4) array of RGBA colors, where each channel (red, green, blue,
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alpha) can assume values between 0 and 1.
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"""
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ifisinstance(c,tuple)andlen(c)==2:
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ifalphaisNone:
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c,alpha=c
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else:
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c=c[0]
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# Special-case inputs that are already arrays, for performance. (If the
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# array has the wrong kind or shape, raise the error during one-at-a-time
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# conversion.)
@@ -464,9 +476,12 @@ def to_rgba_array(c, alpha=None):
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returnnp.array([to_rgba(c,a)forainalpha],float)
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else:
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returnnp.array([to_rgba(c,alpha)],float)
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except(ValueError,TypeError):
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exceptTypeError:
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pass
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exceptValueErrorase:
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ife.args== ("'alpha' must be between 0 and 1, inclusive", ):
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# ValueError is from _to_rgba_no_colorcycle().
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raisee
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ifisinstance(c,str):
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raiseValueError(f"{c!r} is not a valid color value.")
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‎lib/matplotlib/tests/test_colors.py‎

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Original file line numberDiff line numberDiff line change
@@ -1307,6 +1307,51 @@ def test_to_rgba_array_alpha_array():
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assert_array_equal(c[:,3],alpha)
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deftest_to_rgba_array_accepts_color_alpha_tuple():
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assert_array_equal(
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mcolors.to_rgba_array(('black',0.9)),
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[[0,0,0,0.9]])
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deftest_to_rgba_array_explicit_alpha_overrides_tuple_alpha():
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assert_array_equal(
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mcolors.to_rgba_array(('black',0.9),alpha=0.5),
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[[0,0,0,0.5]])
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deftest_to_rgba_array_accepts_color_alpha_tuple_with_multiple_colors():
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color_array=np.array([[1.,1.,1.,1.], [0.,0.,1.,0.]])
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assert_array_equal(
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mcolors.to_rgba_array((color_array,0.2)),
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[[1.,1.,1.,0.2], [0.,0.,1.,0.2]])
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color_sequence= [[1.,1.,1.,1.], [0.,0.,1.,0.]]
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assert_array_equal(
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mcolors.to_rgba_array((color_sequence,0.4)),
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[[1.,1.,1.,0.4], [0.,0.,1.,0.4]])
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deftest_to_rgba_array_error_with_color_invalid_alpha_tuple():
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withpytest.raises(ValueError,match="'alpha' must be between 0 and 1,"):
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mcolors.to_rgba_array(('black',2.0))
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@pytest.mark.parametrize('rgba_alpha',
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[('white',0.5), ('#ffffff',0.5), ('#ffffff00',0.5),
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((1.0,1.0,1.0,1.0),0.5)])
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deftest_to_rgba_accepts_color_alpha_tuple(rgba_alpha):
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assertmcolors.to_rgba(rgba_alpha)== (1,1,1,0.5)
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deftest_to_rgba_explicit_alpha_overrides_tuple_alpha():
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assertmcolors.to_rgba(('red',0.1),alpha=0.9)== (1,0,0,0.9)
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deftest_to_rgba_error_with_color_invalid_alpha_tuple():
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withpytest.raises(ValueError,match="'alpha' must be between 0 and 1"):
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mcolors.to_rgba(('blue',2.0))
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13101355
deftest_failed_conversions():
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withpytest.raises(ValueError):
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mcolors.to_rgba('5')

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