Description

ddale

opened on Jun 20, 2011

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Original report at SourceForge, opened Mon Oct 4 17:04:36 2010

draw_artist on mac os x gives me an error with the following script:

import numpy as np
import matplotlib.pyplot as plt

plt.ion()
plt.figure()
subplot = plt.subplot(1,1,1)
axis = plt.imshow(np.random.random((10,10)))
plt.draw()
subplot.draw_artist(axis)
plt.show()

The traceback is:

Traceback (most recent call last):
File "matplotlib-bug.py", line 8, in
subplot.draw_artist(axis)
File "/Volumes/Data/Local/lib/python2.7/site-packages/matplotlib/axes.py", line 1946, in draw_artist
a.draw(self._cachedRenderer)
File "/Volumes/Data/Local/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in draw_wrapper
draw(artist, renderer, _args, *_kwargs)
File "/Volumes/Data/Local/lib/python2.7/site-packages/matplotlib/image.py", line 338, in draw
gc = renderer.new_gc()
File "/Volumes/Data/Local/lib/python2.7/site-packages/matplotlib/backends/backend_macosx.py", line 105, in new_gc
self.gc.save()
RuntimeError: CGContextRef is NULL

matplotlib version: 1.0.0 (compiled)
python version 2.7 (binary from python.org)
macosx version: 10.6.4

SourceForge Comments

On Tue Oct 5 02:39:48 2010, nicolasrougier wrote:

I got the code from the "Animating selected plot elements" from the scipy cookbook page on animation.
The reason for this code is that I've several subplots to be drawn while I'm running the simulation. I could have used a simple call to plt.draw() but this would redraw the whole figure (is that right ?) and thus I tried to restrict the re-drawing to changing elements since the display is quite slow compared to simualtion.
The same code seems to be working on linux using the gtk backend but maybe it is not supposed to.

On Tue Oct 5 01:31:15 2010, mdehoon wrote:

I think what is happening is that graphics context functions are being called outside of the event loop. This will not work (at least not in the Mac OS X backend), since the graphics context (CGContextRef) is initialized inside the event loop. What exactly are you trying to accomplish? Can you show a full script that you would like to use for your animations? Also, is this script shown in the matplotlib documentation somewhere?

SourceForge History

• On Tue Oct 5 01:31:15 2010, by mdehoon: assigned_to: 100

Activity

1. dmcdougall commented on Sep 23, 2012

   

   dmcdougall

   on Sep 23, 2012

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   Here's some workarounds:

   1. Instead of calling plt.draw() to draw the whole figure. One can call plt.gca() to clear the axis, and then add the updated image to the axis with a call to plt.imshow(blah).

   2. If you want to add a single artist, wouldn't a call to subplot.add_artist() suffice?
2. pelson commented on Sep 23, 2012

   

   pelson

   on Sep 23, 2012

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   Looks like the original issue was @rougier. If you remember the scenario, would you be able to provide some more information (re @mdehoon and @dmcdougall 's questions). Thanks.
3. rougier commented on Sep 23, 2012

   

   rougier

   on Sep 23, 2012

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   What do you mean by scenario ? If this is the original animation file, I'm not sure I still have the code.

   For the original code, I think I use the one from http://www.scipy.org/Cookbook/Matplotlib/Animations (Animating selected plot elements)
4. astrofrog commented on Jun 24, 2013

   

   astrofrog

   on Jun 24, 2013

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   @dmcdougall @pelson - I am running into the same issue with the following code:

   import numpy as np
   
   import matplotlib
   matplotlib.use('MacOSX')
   from matplotlib import pyplot as plt
   
   fig = plt.figure()
   ax = fig.add_subplot(1,1,1)
   image = ax.imshow(np.random.random((128, 128)))
   def test_callback(event):
       ax.draw_artist(image)
   fig.canvas.mpl_connect('button_press_event', test_callback)
   plt.show()
   

   If I click anywhere in the axes (to trigger the callback) I get:

   Traceback (most recent call last):
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/backend_bases.py", line 1785, in button_press_event
       self.callbacks.process(s, mouseevent)
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/cbook.py", line 527, in process
       proxy(*args, **kwargs)
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/cbook.py", line 405, in __call__
       return mtd(*args, **kwargs)
     File "test_draw_artist.py", line 11, in test_callback
       ax.draw_artist(image)
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/axes.py", line 2098, in draw_artist
       a.draw(self._cachedRenderer)
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/artist.py", line 54, in draw_wrapper
       draw(artist, renderer, *args, **kwargs)
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/image.py", line 352, in draw
       gc = renderer.new_gc()
     File "/Users/tom/Library/Python/2.7/lib/python/site-packages/matplotlib-1.4.x-py2.7-macosx-10.6-x86_64.egg/matplotlib/backends/backend_macosx.py", line 97, in new_gc
       self.gc.save()
   RuntimeError: CGContextRef is NULL
   

   This is specific to the MacOSX backend.
5. tacaswell commented on Aug 18, 2014

   

   tacaswell

   on Aug 18, 2014

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   This is the same problem as #2654 and #1266 closing as we have those still open.
6. tacaswell

   closed this as completedon Aug 18, 2014

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