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Commitb511bb2

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Merge pull request#10133 from jklymak/fix-image-scaling
FIX: Image scaling for large dynamic range ints
2 parentse8c57c5 +9ba75dc commitb511bb2

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3 files changed

+32
-8
lines changed

3 files changed

+32
-8
lines changed

‎lib/matplotlib/image.py

Lines changed: 19 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -364,17 +364,25 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
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365365
# TODO slice input array first
366366
inp_dtype=A.dtype
367-
ifinp_dtype.kind=='f':
368-
scaled_dtype=A.dtype
369-
else:
370-
scaled_dtype=np.float32
371-
372367
a_min=A.min()
368+
a_max=A.max()
369+
# figure out the type we should scale to. For floats,
370+
# leave as is. For integers cast to an appropriate-sized
371+
# float. Small integers get smaller floats in an attempt
372+
# to keep the memory footprint reasonable.
373373
ifa_minisnp.ma.masked:
374-
a_min,a_max=0,1# all masked, so values don't matter
374+
# all masked, so values don't matter
375+
a_min,a_max=np.int32(0),np.int32(1)
376+
ifinp_dtype.kind=='f':
377+
scaled_dtype=A.dtype
375378
else:
376-
a_min=a_min.astype(scaled_dtype)
377-
a_max=A.max().astype(scaled_dtype)
379+
# probably an integer of some type.
380+
da=a_max.astype(np.float64)-a_min.astype(np.float64)
381+
ifda>1e8:
382+
# give more breathing room if a big dynamic range
383+
scaled_dtype=np.float64
384+
else:
385+
scaled_dtype=np.float32
378386

379387
# scale the input data to [.1, .9]. The Agg
380388
# interpolators clip to [0, 1] internally, use a
@@ -386,6 +394,9 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
386394
A_scaled=np.empty(A.shape,dtype=scaled_dtype)
387395
A_scaled[:]=A
388396
A_scaled-=a_min
397+
a_min=a_min.astype(scaled_dtype)
398+
a_max=a_max.astype(scaled_dtype)
399+
389400
ifa_min!=a_max:
390401
A_scaled/= ((a_max-a_min)/0.8)
391402
A_scaled+=0.1

‎lib/matplotlib/tests/test_image.py

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -804,6 +804,19 @@ def test_imshow_flatfield():
804804
im.set_clim(.5,1.5)
805805

806806

807+
@image_comparison(baseline_images=['imshow_bignumbers'],
808+
remove_text=True,style='mpl20',
809+
extensions=['png'])
810+
deftest_imshow_bignumbers():
811+
# putting a big number in an array of integers shouldn't
812+
# ruin the dynamic range of the resolved bits.
813+
fig,ax=plt.subplots()
814+
img=np.array([[1,2,1e12],[3,1,4]],dtype=np.uint64)
815+
pc=ax.imshow(img)
816+
pc.set_clim(0,5)
817+
plt.show()
818+
819+
807820
@pytest.mark.parametrize(
808821
"make_norm",
809822
[colors.Normalize,

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