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Commit625bdc7

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Add a helper to copy a colormap and set its extreme colors.
See changelog. See also the number of explicit copies in the examples,which suggest that the old setter-based API is a bit of a footgun (asforgetting to copy seems easy).
1 parentdb06a34 commit625bdc7

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-33
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7 files changed

+48
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,13 @@
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`Colormap.set_extremes` and `Colormap.with_extremes`
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````````````````````````````````````````````````````
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Because the `Colormap.set_bad`, `Colormap.set_under` and `Colormap.set_over`
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methods modify the colormap in place, the user must be careful to first make a
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copy of the colormap if setting the extreme colors e.g. for a builtin colormap.
7+
8+
The new ``Colormap.with_extremes(bad=..., under=..., over=...)`` can be used to
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first copy the colormap and set the extreme colors on that copy.
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11+
The new `Colormap.set_extremes` method is provided for API symmetry with
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`Colormap.with_extremes`, but note that it suffers from the same issue as the
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earlier individual setters.

‎examples/images_contours_and_fields/image_masked.py

Lines changed: 1 addition & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,6 @@
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The second subplot illustrates the use of BoundaryNorm to
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get a filled contour effect.
1010
"""
11-
fromcopyimportcopy
1211

1312
importnumpyasnp
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importmatplotlib.pyplotasplt
@@ -25,11 +24,7 @@
2524
Z= (Z1-Z2)*2
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2726
# Set up a colormap:
28-
# use copy so that we do not mutate the global colormap instance
29-
palette=copy(plt.cm.gray)
30-
palette.set_over('r',1.0)
31-
palette.set_under('g',1.0)
32-
palette.set_bad('b',1.0)
27+
palette=plt.cm.gray.with_extremes(over='r',under='g',bad='b')
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# Alternatively, we could use
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# palette.set_bad(alpha = 0.0)
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# to make the bad region transparent. This is the default.

‎examples/images_contours_and_fields/quadmesh_demo.py

Lines changed: 2 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -9,8 +9,6 @@
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This demo illustrates a bug in quadmesh with masked data.
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"""
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12-
importcopy
13-
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frommatplotlibimportcm,pyplotasplt
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importnumpyasnp
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@@ -30,10 +28,8 @@
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axs[0].pcolormesh(Qx,Qz,Z,shading='gouraud')
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axs[0].set_title('Without masked values')
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33-
# You can control the color of the masked region. We copy the default colormap
34-
# before modifying it.
35-
cmap=copy.copy(cm.get_cmap(plt.rcParams['image.cmap']))
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cmap.set_bad('y',1.0)
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# You can control the color of the masked region.
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cmap=cm.get_cmap(plt.rcParams['image.cmap']).with_extremes(bad='y')
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axs[1].pcolormesh(Qx,Qz,Zm,shading='gouraud',cmap=cmap)
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axs[1].set_title('With masked values')
3935

‎examples/specialty_plots/leftventricle_bulleye.py

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -176,9 +176,8 @@ def bullseye_plot(ax, data, seg_bold=None, cmap=None, norm=None):
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# The second example illustrates the use of a ListedColormap, a
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# BoundaryNorm, and extended ends to show the "over" and "under"
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# value colors.
179-
cmap3=mpl.colors.ListedColormap(['r','g','b','c'])
180-
cmap3.set_over('0.35')
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cmap3.set_under('0.75')
179+
cmap3= (mpl.colors.ListedColormap(['r','g','b','c'])
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.with_extremes(over='0.35',under='0.75'))
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# If a ListedColormap is used, the length of the bounds array must be
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# one greater than the length of the color list. The bounds must be

‎lib/matplotlib/colors.py

Lines changed: 24 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -60,6 +60,7 @@
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"""
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fromcollections.abcimportSized
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importcopy
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importitertools
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importre
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@@ -606,8 +607,7 @@ def __copy__(self):
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returncmapobject
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608609
defset_bad(self,color='k',alpha=None):
609-
"""Set color to be used for masked values.
610-
"""
610+
"""Set color to be used for masked values."""
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self._rgba_bad=to_rgba(color,alpha)
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ifself._isinit:
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self._set_extremes()
@@ -628,6 +628,28 @@ def set_over(self, color='k', alpha=None):
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ifself._isinit:
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self._set_extremes()
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631+
defset_extremes(self,*,bad=None,under=None,over=None):
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"""
633+
Set the colors for masked (*bad*) values and, when ``norm.clip =
634+
False``, low (*under*) and high (*over*) out-of-range values.
635+
"""
636+
ifbadisnotNone:
637+
self.set_bad(bad)
638+
ifunderisnotNone:
639+
self.set_under(under)
640+
ifoverisnotNone:
641+
self.set_over(over)
642+
643+
defwith_extremes(self,*,bad=None,under=None,over=None):
644+
"""
645+
Return a copy of the colormap, for which the colors for masked (*bad*)
646+
values and, when ``norm.clip = False``, low (*under*) and high (*over*)
647+
out-of-range values, have been set accordingly.
648+
"""
649+
new_cm=copy.copy(self)
650+
new_cm.set_extremes(bad=bad,under=under,over=over)
651+
returnnew_cm
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631653
def_set_extremes(self):
632654
ifself._rgba_under:
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self._lut[self._i_under]=self._rgba_under

‎lib/matplotlib/tests/test_image.py

Lines changed: 2 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,4 @@
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fromcontextlibimportExitStack
2-
fromcopyimportcopy
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importio
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importos
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importsys
@@ -769,10 +768,7 @@ def test_mask_image_over_under():
769768
(2*np.pi*0.5*1.5))
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Z=10*(Z2-Z1)# difference of Gaussians
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772-
palette=copy(plt.cm.gray)
773-
palette.set_over('r',1.0)
774-
palette.set_under('g',1.0)
775-
palette.set_bad('b',1.0)
771+
palette=plt.cm.gray.with_extremes(over='r',under='g',bad='b')
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Zm=ma.masked_where(Z>1.2,Z)
777773
fig, (ax1,ax2)=plt.subplots(1,2)
778774
im=ax1.imshow(Zm,interpolation='bilinear',
@@ -830,10 +826,7 @@ def test_imshow_endianess():
830826
remove_text=True,style='mpl20')
831827
deftest_imshow_masked_interpolation():
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833-
cm=copy(plt.get_cmap('viridis'))
834-
cm.set_over('r')
835-
cm.set_under('b')
836-
cm.set_bad('k')
829+
cm=plt.get_cmap('viridis').with_extremes(over='r',under='b',bad='k')
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838831
N=20
839832
n=colors.Normalize(vmin=0,vmax=N*N-1)

‎tutorials/colors/colorbar_only.py

Lines changed: 4 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -64,9 +64,8 @@
6464
fig,ax=plt.subplots(figsize=(6,1))
6565
fig.subplots_adjust(bottom=0.5)
6666

67-
cmap=mpl.colors.ListedColormap(['red','green','blue','cyan'])
68-
cmap.set_over('0.25')
69-
cmap.set_under('0.75')
67+
cmap= (mpl.colors.ListedColormap(['red','green','blue','cyan'])
68+
.with_extremes(over='0.25',under='0.75'))
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7170
bounds= [1,2,4,7,8]
7271
norm=mpl.colors.BoundaryNorm(bounds,cmap.N)
@@ -91,10 +90,8 @@
9190
fig,ax=plt.subplots(figsize=(6,1))
9291
fig.subplots_adjust(bottom=0.5)
9392

94-
cmap=mpl.colors.ListedColormap(['royalblue','cyan',
95-
'yellow','orange'])
96-
cmap.set_over('red')
97-
cmap.set_under('blue')
93+
cmap= (mpl.colors.ListedColormap(['royalblue','cyan','yellow','orange'])
94+
.with_extremes(over='red',under='blue'))
9895

9996
bounds= [-1.0,-0.5,0.0,0.5,1.0]
10097
norm=mpl.colors.BoundaryNorm(bounds,cmap.N)

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