diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
index b1cd08d955a7..16b0377a43bc 100644
--- a/lib/matplotlib/colorbar.py
+++ b/lib/matplotlib/colorbar.py
@@ -1006,24 +1006,34 @@ def _reset_locator_formatter_scale(self):
self.locator = None
self.minorlocator = None
self.formatter = None
- if ((self.spacing == 'uniform') and
- ((self.boundaries is not None) or
- isinstance(self.norm, colors.BoundaryNorm))):
- funcs = (self._forward_boundaries, self._inverse_boundaries)
- self.ax.set_xscale('function', functions=funcs)
- self.ax.set_yscale('function', functions=funcs)
- self.__scale = 'function'
- elif hasattr(self.norm, '_scale') and (self.norm._scale is not None):
+ if (self.boundaries is not None or
+ isinstance(self.norm, colors.BoundaryNorm)):
+ if self.spacing == 'uniform':
+ funcs = (self._forward_boundaries, self._inverse_boundaries)
+ self.ax.set_xscale('function', functions=funcs)
+ self.ax.set_yscale('function', functions=funcs)
+ self.__scale = 'function'
+ elif self.spacing == 'proportional':
+ self.__scale = 'linear'
+ self.ax.set_xscale('linear')
+ self.ax.set_yscale('linear')
+ elif hasattr(self.norm, '_scale') and self.norm._scale is not None:
+ # use the norm's scale:
self.ax.set_xscale(self.norm._scale)
self.ax.set_yscale(self.norm._scale)
self.__scale = self.norm._scale.name
- else:
+ elif type(self.norm) is colors.Normalize:
+ # plain Normalize:
self.ax.set_xscale('linear')
self.ax.set_yscale('linear')
- if type(self.norm) is colors.Normalize:
- self.__scale = 'linear'
- else:
- self.__scale = 'manual'
+ self.__scale = 'linear'
+ else:
+ # norm._scale is None or not an attr: derive the scale from
+ # the Norm:
+ funcs = (self.norm, self.norm.inverse)
+ self.ax.set_xscale('function', functions=funcs)
+ self.ax.set_yscale('function', functions=funcs)
+ self.__scale = 'function'
def _locate(self, x):
"""
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py
index f678a4ffefd5..3b7e5988eab7 100644
--- a/lib/matplotlib/colors.py
+++ b/lib/matplotlib/colors.py
@@ -1152,7 +1152,7 @@ def __init__(self, vmin=None, vmax=None, clip=False):
self.vmin = _sanitize_extrema(vmin)
self.vmax = _sanitize_extrema(vmax)
self.clip = clip
- self._scale = scale.LinearScale(axis=None)
+ self._scale = None # will default to LinearScale for colorbar
@staticmethod
def process_value(value):
@@ -1334,6 +1334,16 @@ def __call__(self, value, clip=None):
result = np.atleast_1d(result)[0]
return result
+ def inverse(self, value):
+ if not self.scaled():
+ raise ValueError("Not invertible until both vmin and vmax are set")
+ (vmin,), _ = self.process_value(self.vmin)
+ (vmax,), _ = self.process_value(self.vmax)
+ (vcenter,), _ = self.process_value(self.vcenter)
+
+ result = np.interp(value, [0, 0.5, 1.], [vmin, vcenter, vmax])
+ return result
+
class CenteredNorm(Normalize):
def __init__(self, vcenter=0, halfrange=None, clip=False):
diff --git a/lib/matplotlib/tests/baseline_images/test_colorbar/colorbar_twoslope.png b/lib/matplotlib/tests/baseline_images/test_colorbar/colorbar_twoslope.png
new file mode 100644
index 000000000000..27d9227dcfe0
Binary files /dev/null and b/lib/matplotlib/tests/baseline_images/test_colorbar/colorbar_twoslope.png differ
diff --git a/lib/matplotlib/tests/test_colorbar.py b/lib/matplotlib/tests/test_colorbar.py
index ac054755c4c1..6167618575dd 100644
--- a/lib/matplotlib/tests/test_colorbar.py
+++ b/lib/matplotlib/tests/test_colorbar.py
@@ -771,3 +771,17 @@ def test_inset_colorbar_layout():
np.testing.assert_allclose(cb.ax.get_position().bounds,
[0.87, 0.342, 0.0237, 0.315], atol=0.01)
assert cb.ax.outer_ax in ax.child_axes
+
+
+@image_comparison(['colorbar_twoslope.png'], remove_text=True,
+ style='mpl20')
+def test_twoslope_colorbar():
+ # Note that the first tick = 20, and should be in the middle
+ # of the colorbar (white)
+ fig, ax = plt.subplots()
+
+ norm = mcolors.TwoSlopeNorm(20, 0, 100)
+ pc = ax.pcolormesh(np.arange(1, 11), np.arange(1, 11),
+ np.arange(100).reshape(10, 10),
+ norm=norm, cmap='RdBu_r')
+ fig.colorbar(pc)
diff --git a/lib/matplotlib/tests/test_colors.py b/lib/matplotlib/tests/test_colors.py
index 81dd65bab713..ae004e957591 100644
--- a/lib/matplotlib/tests/test_colors.py
+++ b/lib/matplotlib/tests/test_colors.py
@@ -1406,6 +1406,5 @@ def test_norm_deepcopy():
norm = mcolors.Normalize()
norm.vmin = 0.0002
norm2 = copy.deepcopy(norm)
- assert isinstance(norm2._scale, mscale.LinearScale)
+ assert norm2._scale is None
assert norm2.vmin == norm.vmin
- assert norm2._scale is not norm._scale
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