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Showing np.uint16 images of the form (h,w,3) is broken #2499

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luispedro opened this issue Oct 6, 2013 · 4 comments
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Showing np.uint16 images of the form (h,w,3) is broken #2499

luispedro opened this issue Oct 6, 2013 · 4 comments
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@efiring
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API: changes
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v2.1

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@luispedro
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Here is a simple test case:

import matplotlib.pyplot as plt
import numpy as np
A = np.array([np.arange(256,dtype=np.uint16) for _ in xrange(256)])
B =  (A<<8)+(255*np.random.random(A.shape)).astype(np.uint16)
B = np.dstack([B,B,B])
plt.imshow(B)
plt.show()

This results in random bits.

The problem is in file lib/matplotlib.cm.py: the conversion to np.uint8 assumes that the input is in 0..1 format.
@luispedro luispedro mentioned this issue Oct 6, 2013
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@tacaswell
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To be fair, the docs (http://matplotlib.org/api/axes_api.html#matplotlib.axes.Axes.imshow) only claim to support float or uint8 so I would not call this broken.

@luispedro
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Then, maybe the real bug is that it doesn't raise an exception :)

It's certainly surprising behaviour.

luispedro added a commit to luispedro/matplotlib that referenced this issue Oct 8, 2013
@luispedro
BUG Raise exception for invalid input
46ac856 
Arrays of non-uint8 types were assumed to be in 0..1 range, resulting in
the small bits being showing when this was not true. Now, an explicit
exception is raised.

Closes issue matplotlib#2499
@tacaswell
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@luispedro Can you make a PR with that fix?

luispedro added a commit to luispedro/matplotlib that referenced this issue Nov 30, 2013
@luispedro
BUG Raise exception for invalid input
f96500a 
Arrays of non-uint8 types were assumed to be in 0..1 range, resulting in
the small bits being showing when this was not true. Now, an explicit
exception is raised.

Closes issue matplotlib#2499
@luispedro luispedro mentioned this issue Nov 30, 2013
Closed
luispedro added a commit to luispedro/matplotlib that referenced this issue Nov 30, 2013
@luispedro
BUG Raise exception for invalid input
eb2480a 
Arrays of non-uint8 types were assumed to be in 0..1 range.

When this was not true and integer values were used, only the low-order
bits were used, resulting in a mangled image. Now, an explicit exception
is raised.

Closes issue matplotlib#2499
@luispedro luispedro mentioned this issue Nov 30, 2013
Closed
@tacaswell tacaswell added this to the v1.5.x milestone Aug 17, 2014
@luispedro luispedro mentioned this issue Jul 23, 2015
Closed
efiring pushed a commit to efiring/matplotlib that referenced this issue Mar 7, 2016
@luispedro @efiring
BUG Raise exception for invalid input
8433eec 
Arrays of non-uint8 types were assumed to be in 0..1 range.

When this was not true and integer values were used, only the low-order
bits were used, resulting in a mangled image. Now, an explicit exception
is raised.

Closes issue matplotlib#2499
efiring added a commit to efiring/matplotlib that referenced this issue Mar 7, 2016
@efiring
MNT: improve image array argument checking in to_rgba. Closes matplot…
86f65ce 
…lib#2499.
@efiring efiring self-assigned this Mar 7, 2016
tacaswell added a commit that referenced this issue Mar 7, 2016
@tacaswell
Merge pull request #6122 from efiring/update_2632_2
7df8f0d 
MNT: improve image array argument checking in to_rgba. Closes #2499.
@tacaswell
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@luispedro Thanks, sorry this took so long to get resolved.

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