Description

astrofrog

opened on Apr 29, 2011

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If I run the following example

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(1,2,1)
image = plt.imread('2mass_rgb.png')
ax.imshow(image, origin='upper', extent=[0.5,723.5,0.5,724.5])

ax = fig.add_subplot(1,2,2)
image = plt.imread('2mass_rgb.jpg')
ax.imshow(image, origin='upper', extent=[0.5,723.5,0.5,724.5])

fig.savefig('rgb.png')

the left and right hand subplots show the RGB image flipped a different way. This does not happen if I use PIL to read in the image using Image.open, so presumably it is a bug in imread? The files I am using can be found here.

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1. mdboom commented on Apr 29, 2011

   

   mdboom

   on Apr 29, 2011

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   JPG loading is handled through PIL, and the pil_to_array code explicitly flips the image upside down. This seems like a bug, but I'm hesitant to fix it since it's been that way for at least 3 years in a commit by @jdh2358 -- I'm surprised we're just finding it now -- and this isn't an area I'm terribly familiar with.

   diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
   index f2d9984..93402d4 100644
   --- a/lib/matplotlib/image.py
   +++ b/lib/matplotlib/image.py
   @@ -1257,7 +1257,7 @@ def pil_to_array( pilImage ):
        """
        def toarray(im):
            'return a 1D array of floats'
   -        x_str = im.tostring('raw',im.mode,0,-1)
   +        x_str = im.tostring()
            x = np.fromstring(x_str,np.uint8)
            return x
    
2. leejjoon commented on May 1, 2011

   

   leejjoon

   on May 1, 2011

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   I think the thread below is related with this issue. I don't think we actually made any action though.

   http://old.nabble.com/Question-about-imshow-ts23578564.html
3. ghost assigned

   mdboom

   on Jun 15, 2011
4. ghost assigned

   astraw

   on Jun 20, 2011
5. mdboom commented on Jun 20, 2011

   

   mdboom

   on Jun 20, 2011

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   Changing assignment to Andrew, since I don't quite understand the history and backward incompatibility issues.
6. stefanv commented on Sep 19, 2011

   

   stefanv

   on Sep 19, 2011

   Contributor

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   I can verify that this is a bug. Here's the much simplified version we use in scikits.image:

   https://github.com/scikits-image/scikits.image/blob/master/scikits/image/io/_plugins/pil_plugin.py#L12
7. mdboom commented on Jun 1, 2012

   

   mdboom

   on Jun 1, 2012

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   I believe this is fixed by #616.
8. pelson commented on Jun 10, 2012

   

   pelson

   on Jun 10, 2012

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   I can confirm that this was fixed 5 days ago.
9. pelson

   closed this as completedon Jun 10, 2012
10. mdboom commented on Jun 11, 2012

    

    mdboom

    on Jun 11, 2012

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    Just a note: as this is a pretty significant backward-incompatible change, it is only on master, and won't be in the 1.1.2rc.
11. magnunor

    added a commit that references this issue on Dec 5, 2013

    Merge pull request matplotlib#101 from francisco-dlp/ENH_toolkit_choice

    611f11c

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