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Fixed large pcolormesh rendering with bbox_inches='tight'.#4045

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tacaswell merged 1 commit intomatplotlib:v1.4.xfrom
pelson:quadmesh_big
Jan 31, 2015
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Fixed large pcolormesh rendering with bbox_inches='tight'.#4045
tacaswell merged 1 commit intomatplotlib:v1.4.xfrom
pelson:quadmesh_big

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@pelson pelson commented Jan 28, 2015

Replaces #4017.
Closes #3095.

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@pelson pelson added this to the v1.4.3 milestone Jan 28, 2015
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tacaswell commented Jan 28, 2015

This does not account for having a non-trivial offset array.

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pelson commented Jan 28, 2015

This does not account for having a non-trivial offset array.

Can you provide a simple example? I've never properly understood the offsets in some collection contexts.

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tacaswell commented Jan 29, 2015 

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots(1, 1)

X, Y = np.meshgrid(range(25), range(20))

C = np.random.rand(*X.shape)
offsets = (np.random.randn(2, 24*19) 

ax.pcolormesh(X, Y, C, offsets=offsets, transOffset=ax.transData)

so

which has an odd extra shift from (0, 0) to (3, 2.3) for the lower left. I am also not really clear on why this is useful, but it is something that the code does.

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tacaswell commented Jan 29, 2015

The code for this in agg ends up in c++ layer and gets really hairy really fast.

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tacaswell commented Jan 29, 2015 

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots(1, 1)

X, Y = np.meshgrid(range(25), range(20))

C = np.random.rand(*X.shape)
offsets = np.random.randn(24*19, 2) * .1

ax.pcolormesh(X, Y, C)#, offsets=offsets, transOffset=ax.transData)
fig.savefig('so.png', bbox_inches='tight')

gives me

<ipython-input-26-382f89238547> in <module>()
----> 1 exec(compile(open('/tmp/ipython-5366aRU.py').read(), '/tmp/ipython-5366aRU.py', 'exec')) # PYTHON-MODE

/tmp/ipython-5366aRU.py in <module>()

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/figure.pyc in savefig(self, *args, **kwargs)
   1474             self.set_frameon(frameon)
   1475 
-> 1476         self.canvas.print_figure(*args, **kwargs)
   1477 
   1478         if frameon:

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5agg.pyc in print_figure(self, *args, **kwargs)
    159 
    160     def print_figure(self, *args, **kwargs):
--> 161         FigureCanvasAgg.print_figure(self, *args, **kwargs)
    162         self.draw()
    163 

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/backend_bases.pyc in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2166                 bbox_filtered = []
   2167                 for a in bbox_artists:
-> 2168                     bbox = a.get_window_extent(renderer)
   2169                     if a.get_clip_on():
   2170                         clip_box = a.get_clip_box()

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/collections.pyc in get_window_extent(self, renderer)
    208         # TODO:check to ensure that this does not fail for
    209         # cases other than scatter plot legend
--> 210         return self.get_datalim(transforms.IdentityTransform())
    211 
    212     def _prepare_points(self):

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/collections.pyc in get_datalim(self, transData)
   1707 
   1708     def get_datalim(self, transData):
-> 1709         return (self.get_transform() - transData).transform_bbox(self._bbox)
   1710 
   1711     @staticmethod

/home/tcaswell/.virtualenvs/mpl_master_3k/lib/python2.7/site-packages/matplotlib-1.4.x.dev0-py2.7-linux-x86_64.egg/matplotlib/transforms.pyc in transform_bbox(self, bbox)
   1352         requirement for matplotlib figures), see :class:`TransformedBbox`.
   1353         """
-> 1354         return Bbox(self._transform.transform(bbox.get_points()))
   1355 
   1356     def get_affine(self):

AttributeError: 'CompositeGenericTransform' object has no attribute '_transform'

tacaswell
tacaswell reviewed Jan 29, 2015
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@tacaswell tacaswell Jan 29, 2015

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I think this line should be return Bbox(self..transform(bbox.get_points()))

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@pelson pelson Jan 29, 2015

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Agreed.

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pelson commented Jan 29, 2015

Thanks for the example @tacaswell. I did not know you could do that!
I'll take a look at dealing with the offsets, but ultimately if this is holding up a release, I'd be comfortable trading a major performance bug with pcolormesh, for a minor cut-off known bug with a not-well-used part of the same routine.

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tacaswell commented Jan 29, 2015

I concur about the trade off.

@tacaswell tacaswell added the Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions. label Jan 31, 2015
@tacaswell tacaswell merged commit 44ff97e into matplotlib:v1.4.x Jan 31, 2015
tacaswell added a commit that referenced this pull request Jan 31, 2015
@tacaswell
Merge pull request #4045 from pelson/quadmesh_big
cad373f 
BUG : Fix run-away memory usage with pcolormesh + bbox_inches='tight'
@tacaswell tacaswell mentioned this pull request Jan 31, 2015
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@pelson pelson deleted the quadmesh_big branch February 1, 2015 22:54
@pelson pelson mentioned this pull request Jan 5, 2016
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