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Backport PR #16344 on branch v3.2.x (Cast vmin/vmax to floats before nonsingular-expanding them.) #16364

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Merged
merged 1 commit into from
Jan 29, 2020
Merged

Backport PR #16344 on branch v3.2.x (Cast vmin/vmax to floats before nonsingular-expanding them.) #16364

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11 changes: 11 additions & 0 deletions lib/matplotlib/tests/test_colorbar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -580,3 +580,14 @@ def test_colorbar_label():

cbar3 = fig.colorbar(im, orientation='horizontal', label='horizontal cbar')
assert cbar3.ax.get_xlabel() == 'horizontal cbar'


@pytest.mark.parametrize("clim", [(-20000, 20000), (-32768, 0)])
def test_colorbar_int(clim):
# Check that we cast to float early enough to not
# overflow ``int16(20000) - int16(-20000)`` or
# run into ``abs(int16(-32768)) == -32768``.
fig, ax = plt.subplots()
im = ax.imshow([[*map(np.int16, clim)]])
fig.colorbar(im)
assert (im.norm.vmin, im.norm.vmax) == clim
4 changes: 4 additions & 0 deletions lib/matplotlib/transforms.py
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Expand Up @@ -2812,6 +2812,10 @@ def nonsingular(vmin, vmax, expander=0.001, tiny=1e-15, increasing=True):
vmin, vmax = vmax, vmin
swapped = True

# Expand vmin, vmax to float: if they were integer types, they can wrap
# around in abs (abs(np.int8(-128)) == -128) and vmax - vmin can overflow.
vmin, vmax = map(float, [vmin, vmax])

maxabsvalue = max(abs(vmin), abs(vmax))
if maxabsvalue < (1e6 / tiny) * np.finfo(float).tiny:
vmin = -expander
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