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Support imshow(<float16 array>). #20290

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Merged
merged 1 commit into from
May 26, 2021
Merged

Support imshow(<float16 array>). #20290

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14 changes: 6 additions & 8 deletions lib/matplotlib/image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -411,14 +411,12 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
# all masked, so values don't matter
a_min, a_max = np.int32(0), np.int32(1)
if inp_dtype.kind == 'f':
scaled_dtype = A.dtype
# Cast to float64
if A.dtype not in (np.float32, np.float16):
if A.dtype != np.float64:
_api.warn_external(
f"Casting input data from '{A.dtype}' to "
f"'float64' for imshow")
scaled_dtype = np.float64
scaled_dtype = np.dtype(
np.float64 if A.dtype.itemsize > 4 else np.float32)
if scaled_dtype.itemsize < A.dtype.itemsize:
_api.warn_external(
f"Casting input data from {A.dtype} to "
f"{scaled_dtype} for imshow")
else:
# probably an integer of some type.
da = a_max.astype(np.float64) - a_min.astype(np.float64)
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7 changes: 7 additions & 0 deletions lib/matplotlib/tests/test_image.py
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Expand Up @@ -993,6 +993,13 @@ def test_empty_imshow(make_norm):
im.make_image(fig._cachedRenderer)


def test_imshow_float16():
fig, ax = plt.subplots()
ax.imshow(np.zeros((3, 3), dtype=np.float16))
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This warns too? Should you check for the warning?

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No, this doesn't warn because it's an upcast (just like we don't warn for int->float).
(Unchecked warnings normally cause tests to fail, so this also tests that no warning is emitted.)

# Ensure that drawing doesn't cause crash.
fig.canvas.draw()


def test_imshow_float128():
fig, ax = plt.subplots()
ax.imshow(np.zeros((3, 3), dtype=np.longdouble))
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