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jklymakjklymak
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TST: fix image tests
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‎doc/api/next_api_changes/2019-07-17-JMK.rst

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
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Default interpolation for `image` is new "antialiased" option
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-------------------------------------------------------------
3+
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Images displayed in Matplotlib previously used nearest-neighbor
5+
interpolation, leading to aliasing effects for non-integer upscaling, and
6+
single dots being lost.
7+
8+
New default for :rc:`image.interpolation` is the new option "antialiased".
9+
`imshow(A, interpolation='antialiased')` will apply a Hanning filter when
10+
resampling the data in A for display (or saving to file) *if* the upsample
11+
rate is less than a factor of three, and not an integer; downsampled data is
12+
always smoothed at resampling.
13+
14+
To get the old behavior, set :rc:`interpolation` to the old default "nearest"
15+
(or speciful the ``interpolation`` kwarg of `.Axes.imshow`)
16+
17+
To always get the anti-aliasing behavior, no matter what the up/down sample
18+
rate, set :rc:`interpolation` to "hanning" (or one of the other filters
19+
available.
20+
21+
Note that the "hanning" filter was chosen because it has only a modest
22+
performance penalty. Anti-aliasing can be improved with other filters.

‎lib/matplotlib/tests/test_axes.py

Lines changed: 78 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -3764,21 +3764,24 @@ def test_specgram_freqs():
37643764
ax23 = fig2.add_subplot(3, 1, 3)
37653765

37663766
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3767-
pad_to=pad_to, sides='default')
3767+
pad_to=pad_to, sides='default', interpolation='nearest')
37683768
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3769-
pad_to=pad_to, sides='onesided')
3769+
pad_to=pad_to, sides='onesided', interpolation='nearest')
37703770
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3771-
pad_to=pad_to, sides='twosided')
3771+
pad_to=pad_to, sides='twosided', interpolation='nearest')
37723772

37733773
ax21.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
37743774
pad_to=pad_to, sides='default',
3775-
scale='linear', norm=matplotlib.colors.LogNorm())
3775+
scale='linear', norm=matplotlib.colors.LogNorm(),
3776+
interpolation='nearest')
37763777
ax22.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
37773778
pad_to=pad_to, sides='onesided',
3778-
scale='linear', norm=matplotlib.colors.LogNorm())
3779+
scale='linear', norm=matplotlib.colors.LogNorm(),
3780+
interpolation='nearest')
37793781
ax23.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
37803782
pad_to=pad_to, sides='twosided',
3781-
scale='linear', norm=matplotlib.colors.LogNorm())
3783+
scale='linear', norm=matplotlib.colors.LogNorm(),
3784+
interpolation='nearest')
37823785

37833786

37843787
@image_comparison(['specgram_noise.png', 'specgram_noise_linear.png'],
@@ -3810,21 +3813,24 @@ def test_specgram_noise():
38103813
ax23 = fig2.add_subplot(3, 1, 3)
38113814

38123815
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3813-
pad_to=pad_to, sides='default')
3816+
pad_to=pad_to, sides='default', interpolation='nearest')
38143817
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3815-
pad_to=pad_to, sides='onesided')
3818+
pad_to=pad_to, sides='onesided', interpolation='nearest')
38163819
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3817-
pad_to=pad_to, sides='twosided')
3820+
pad_to=pad_to, sides='twosided', interpolation='nearest')
38183821

38193822
ax21.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38203823
pad_to=pad_to, sides='default',
3821-
scale='linear', norm=matplotlib.colors.LogNorm())
3824+
scale='linear', norm=matplotlib.colors.LogNorm(),
3825+
interpolation='nearest')
38223826
ax22.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38233827
pad_to=pad_to, sides='onesided',
3824-
scale='linear', norm=matplotlib.colors.LogNorm())
3828+
scale='linear', norm=matplotlib.colors.LogNorm(),
3829+
interpolation='nearest')
38253830
ax23.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38263831
pad_to=pad_to, sides='twosided',
3827-
scale='linear', norm=matplotlib.colors.LogNorm())
3832+
scale='linear', norm=matplotlib.colors.LogNorm(),
3833+
interpolation='nearest')
38283834

38293835

38303836
@image_comparison(['specgram_magnitude_freqs.png',
@@ -3865,21 +3871,27 @@ def test_specgram_magnitude_freqs():
38653871
ax23 = fig2.add_subplot(3, 1, 3)
38663872

38673873
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3868-
pad_to=pad_to, sides='default', mode='magnitude')
3874+
pad_to=pad_to, sides='default', mode='magnitude',
3875+
interpolation='nearest')
38693876
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3870-
pad_to=pad_to, sides='onesided', mode='magnitude')
3877+
pad_to=pad_to, sides='onesided', mode='magnitude',
3878+
interpolation='nearest')
38713879
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3872-
pad_to=pad_to, sides='twosided', mode='magnitude')
3880+
pad_to=pad_to, sides='twosided', mode='magnitude',
3881+
interpolation='nearest')
38733882

38743883
ax21.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38753884
pad_to=pad_to, sides='default', mode='magnitude',
3876-
scale='linear', norm=matplotlib.colors.LogNorm())
3885+
scale='linear', norm=matplotlib.colors.LogNorm(),
3886+
interpolation='nearest')
38773887
ax22.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38783888
pad_to=pad_to, sides='onesided', mode='magnitude',
3879-
scale='linear', norm=matplotlib.colors.LogNorm())
3889+
scale='linear', norm=matplotlib.colors.LogNorm(),
3890+
interpolation='nearest')
38803891
ax23.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
38813892
pad_to=pad_to, sides='twosided', mode='magnitude',
3882-
scale='linear', norm=matplotlib.colors.LogNorm())
3893+
scale='linear', norm=matplotlib.colors.LogNorm(),
3894+
interpolation='nearest')
38833895

38843896

38853897
@image_comparison(['specgram_magnitude_noise.png',
@@ -3912,21 +3924,27 @@ def test_specgram_magnitude_noise():
39123924
ax23 = fig2.add_subplot(3, 1, 3)
39133925

39143926
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3915-
pad_to=pad_to, sides='default', mode='magnitude')
3927+
pad_to=pad_to, sides='default', mode='magnitude',
3928+
interpolation='nearest')
39163929
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3917-
pad_to=pad_to, sides='onesided', mode='magnitude')
3930+
pad_to=pad_to, sides='onesided', mode='magnitude',
3931+
interpolation='nearest')
39183932
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3919-
pad_to=pad_to, sides='twosided', mode='magnitude')
3933+
pad_to=pad_to, sides='twosided', mode='magnitude',
3934+
interpolation='nearest')
39203935

39213936
ax21.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
39223937
pad_to=pad_to, sides='default', mode='magnitude',
3923-
scale='linear', norm=matplotlib.colors.LogNorm())
3938+
scale='linear', norm=matplotlib.colors.LogNorm(),
3939+
interpolation='nearest')
39243940
ax22.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
39253941
pad_to=pad_to, sides='onesided', mode='magnitude',
3926-
scale='linear', norm=matplotlib.colors.LogNorm())
3942+
scale='linear', norm=matplotlib.colors.LogNorm(),
3943+
interpolation='nearest')
39273944
ax23.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
39283945
pad_to=pad_to, sides='twosided', mode='magnitude',
3929-
scale='linear', norm=matplotlib.colors.LogNorm())
3946+
scale='linear', norm=matplotlib.colors.LogNorm(),
3947+
interpolation='nearest')
39303948

39313949

39323950
@image_comparison(['specgram_angle_freqs.png'],
@@ -3961,26 +3979,29 @@ def test_specgram_angle_freqs():
39613979
ax13 = fig1.add_subplot(3, 1, 3)
39623980

39633981
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3964-
pad_to=pad_to, sides='default', mode='angle')
3982+
pad_to=pad_to, sides='default', mode='angle',
3983+
interpolation='nearest')
39653984
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3966-
pad_to=pad_to, sides='onesided', mode='angle')
3985+
pad_to=pad_to, sides='onesided', mode='angle',
3986+
interpolation='nearest')
39673987
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
3968-
pad_to=pad_to, sides='twosided', mode='angle')
3988+
pad_to=pad_to, sides='twosided', mode='angle',
3989+
interpolation='nearest')
39693990

39703991
with pytest.raises(ValueError):
39713992
ax11.specgram(y, NFFT=NFFT, Fs=Fs,
39723993
noverlap=noverlap, pad_to=pad_to, sides='default',
3973-
mode='phase', scale='dB')
3994+
mode='phase', scale='dB', interpolation='nearest')
39743995

39753996
with pytest.raises(ValueError):
39763997
ax12.specgram(y, NFFT=NFFT, Fs=Fs,
39773998
noverlap=noverlap, pad_to=pad_to, sides='onesided',
3978-
mode='phase', scale='dB')
3999+
mode='phase', scale='dB', interpolation='nearest')
39794000

39804001
with pytest.raises(ValueError):
39814002
ax13.specgram(y, NFFT=NFFT, Fs=Fs,
39824003
noverlap=noverlap, pad_to=pad_to, sides='twosided',
3983-
mode='phase', scale='dB')
4004+
mode='phase', scale='dB', interpolation='nearest')
39844005

39854006

39864007
@image_comparison(['specgram_angle_noise.png'],
@@ -4007,26 +4028,29 @@ def test_specgram_noise_angle():
40074028
ax13 = fig1.add_subplot(3, 1, 3)
40084029

40094030
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4010-
pad_to=pad_to, sides='default', mode='angle')
4031+
pad_to=pad_to, sides='default', mode='angle',
4032+
interpolation='nearest')
40114033
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4012-
pad_to=pad_to, sides='onesided', mode='angle')
4034+
pad_to=pad_to, sides='onesided', mode='angle',
4035+
interpolation='nearest')
40134036
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4014-
pad_to=pad_to, sides='twosided', mode='angle')
4037+
pad_to=pad_to, sides='twosided', mode='angle',
4038+
interpolation='nearest')
40154039

40164040
with pytest.raises(ValueError):
40174041
ax11.specgram(y, NFFT=NFFT, Fs=Fs,
40184042
noverlap=noverlap, pad_to=pad_to, sides='default',
4019-
mode='phase', scale='dB')
4043+
mode='phase', scale='dB', interpolation='nearest')
40204044

40214045
with pytest.raises(ValueError):
40224046
ax12.specgram(y, NFFT=NFFT, Fs=Fs,
40234047
noverlap=noverlap, pad_to=pad_to, sides='onesided',
4024-
mode='phase', scale='dB')
4048+
mode='phase', scale='dB', interpolation='nearest')
40254049

40264050
with pytest.raises(ValueError):
40274051
ax13.specgram(y, NFFT=NFFT, Fs=Fs,
40284052
noverlap=noverlap, pad_to=pad_to, sides='twosided',
4029-
mode='phase', scale='dB')
4053+
mode='phase', scale='dB', interpolation='nearest')
40304054

40314055

40324056
@image_comparison(['specgram_phase_freqs.png'],
@@ -4061,26 +4085,29 @@ def test_specgram_freqs_phase():
40614085
ax13 = fig1.add_subplot(3, 1, 3)
40624086

40634087
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4064-
pad_to=pad_to, sides='default', mode='phase')
4088+
pad_to=pad_to, sides='default', mode='phase',
4089+
interpolation='nearest')
40654090
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4066-
pad_to=pad_to, sides='onesided', mode='phase')
4091+
pad_to=pad_to, sides='onesided', mode='phase',
4092+
interpolation='nearest')
40674093
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4068-
pad_to=pad_to, sides='twosided', mode='phase')
4094+
pad_to=pad_to, sides='twosided', mode='phase',
4095+
interpolation='nearest')
40694096

40704097
with pytest.raises(ValueError):
40714098
ax11.specgram(y, NFFT=NFFT, Fs=Fs,
40724099
noverlap=noverlap, pad_to=pad_to, sides='default',
4073-
mode='phase', scale='dB')
4100+
mode='phase', scale='dB', interpolation='nearest')
40744101

40754102
with pytest.raises(ValueError):
40764103
ax12.specgram(y, NFFT=NFFT, Fs=Fs,
40774104
noverlap=noverlap, pad_to=pad_to, sides='onesided',
4078-
mode='phase', scale='dB')
4105+
mode='phase', scale='dB', interpolation='nearest')
40794106

40804107
with pytest.raises(ValueError):
40814108
ax13.specgram(y, NFFT=NFFT, Fs=Fs,
40824109
noverlap=noverlap, pad_to=pad_to, sides='twosided',
4083-
mode='phase', scale='dB')
4110+
mode='phase', scale='dB', interpolation='nearest')
40844111

40854112

40864113
@image_comparison(['specgram_phase_noise.png'],
@@ -4107,26 +4134,29 @@ def test_specgram_noise_phase():
41074134
ax13 = fig1.add_subplot(3, 1, 3)
41084135

41094136
ax11.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4110-
pad_to=pad_to, sides='default', mode='phase')
4137+
pad_to=pad_to, sides='default', mode='phase',
4138+
interpolation='nearest')
41114139
ax12.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4112-
pad_to=pad_to, sides='onesided', mode='phase')
4140+
pad_to=pad_to, sides='onesided', mode='phase',
4141+
interpolation='nearest')
41134142
ax13.specgram(y, NFFT=NFFT, Fs=Fs, noverlap=noverlap,
4114-
pad_to=pad_to, sides='twosided', mode='phase')
4143+
pad_to=pad_to, sides='twosided', mode='phase',
4144+
interpolation='nearest')
41154145

41164146
with pytest.raises(ValueError):
41174147
ax11.specgram(y, NFFT=NFFT, Fs=Fs,
41184148
noverlap=noverlap, pad_to=pad_to, sides='default',
4119-
mode='phase', scale='dB')
4149+
mode='phase', scale='dB', interpolation='nearest')
41204150

41214151
with pytest.raises(ValueError):
41224152
ax12.specgram(y, NFFT=NFFT, Fs=Fs,
41234153
noverlap=noverlap, pad_to=pad_to, sides='onesided',
4124-
mode='phase', scale='dB')
4154+
mode='phase', scale='dB', interpolation='nearest')
41254155

41264156
with pytest.raises(ValueError):
41274157
ax13.specgram(y, NFFT=NFFT, Fs=Fs,
41284158
noverlap=noverlap, pad_to=pad_to, sides='twosided',
4129-
mode='phase', scale='dB')
4159+
mode='phase', scale='dB', interpolation='nearest')
41304160

41314161

41324162
@image_comparison(['psd_freqs.png'], remove_text=True)

‎lib/matplotlib/tests/test_image.py

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -503,7 +503,8 @@ def test_bbox_image_inverted():
503503

504504
fig, ax = plt.subplots()
505505
bbox_im = BboxImage(
506-
TransformedBbox(Bbox([[100, 100], [0, 0]]), ax.transData))
506+
TransformedBbox(Bbox([[100, 100], [0, 0]]), ax.transData),
507+
interpolation='nearest')
507508
bbox_im.set_data(image)
508509
bbox_im.set_clip_on(False)
509510
ax.set_xlim(0, 100)
@@ -513,7 +514,8 @@ def test_bbox_image_inverted():
513514
image = np.identity(10)
514515

515516
bbox_im = BboxImage(TransformedBbox(Bbox([[0.1, 0.2], [0.3, 0.25]]),
516-
ax.figure.transFigure))
517+
ax.figure.transFigure),
518+
interpolation='nearest')
517519
bbox_im.set_data(image)
518520
bbox_im.set_clip_on(False)
519521
ax.add_artist(bbox_im)
@@ -855,8 +857,10 @@ def test_imshow_masked_interpolation():
855857
data = np.ma.masked_array(data, mask)
856858

857859
fig, ax_grid = plt.subplots(3, 6)
860+
interps = mimage._interpd_
861+
interps.pop('antialiased', None)
858862

859-
for interp, ax in zip(sorted(mimage._interpd_), ax_grid.ravel()):
863+
for interp, ax in zip(sorted(interps), ax_grid.ravel()):
860864
ax.set_title(interp)
861865
ax.imshow(data, norm=n, cmap=cm, interpolation=interp)
862866
ax.axis('off')

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