Hi Thomas,
As explained in this issue:
https://github.com/matplotlib/matplotlib/issues/166
draw_artist does not work because it is being called from outside the event
loop (or, to be exact, because draw_artist will only work if it is called from
inside the drawing callback function that is called by the event loop). On some
backends, you may get away with calling draw_artist from outside the event
loop. However, this suggests a problem in the code design (for comparison, see
this issue
https://github.com/matplotlib/matplotlib/issues/531
on the animation code).
As far as I know, the matplotlib documentation does not advertise the use of
draw_artist, and there is no guarantee that it will work on all backends. If
you can redesign your code such that draw_artist is called from inside the
event loop, it should work OK on all backends. (though my first bet would also
be to look at draw_idle).
Best,
-Michiel.
________________________________
From: Thomas Robitaille <thomas.robitai...@gmail.com>
To: Michael Droettboom <md...@stsci.edu>
Cc: matplotlib-users@lists.sourceforge.net
Sent: Tuesday, June 25, 2013 9:45 PM
Subject: Re: [Matplotlib-users] Making an interactive plot faster
Hi Mike,
Thanks for the suggestion - however, this doesn't change the FPS. From
my experiments so far, it seems using draw_artist would be the best
bet, but any ideas why it doesn't work with the MacOS X backend?
https://github.com/matplotlib/matplotlib/issues/166
Cheers,
Tom
On 24 June 2013 16:13, Michael Droettboom <md...@stsci.edu> wrote:
> Have you tried using "draw_idle"? That will schedule the draw for the
> next time the event loop is idle.
>
> Mike
>
> On 06/24/2013 07:39 AM, Thomas Robitaille wrote:
>> Hi everyone,
>>
>> The following shows an example of a simple data viewer which includes
>> a slider, a bitmap, and a scatter plot:
>>
>> """
>> import numpy as np
>> from matplotlib import pyplot as plt
>> from matplotlib.widgets import Slider
>>
>> fig = plt.figure()
>>
>> ax1 = fig.add_axes([0.1, 0.1, 0.4, 0.7])
>> image = ax1.imshow(np.random.random((512, 512)), vmin=0., vmax=1.)
>>
>> ax2 = fig.add_axes([0.1, 0.9, 0.85, 0.05])
>> ax2.set_xticklabels("")
>> ax2.set_yticklabels("")
>> slider = Slider(ax2, "", 0., 1.)
>>
>> def update_vmax(value):
>> image.set_clim(0., value)
>> fig.canvas.draw()
>>
>> slider.on_changed(update_vmax)
>>
>> ax3 = fig.add_axes([0.55, 0.1, 0.4, 0.7])
>> x = np.random.random(10000)
>> y = np.random.random(10000)
>> ax3.scatter(x, y)
>>
>> plt.show()
>> """
>>
>> When moving the slider, the vmax of the image changes, but I get very
>> slow frame rates (~2/sec) on my computer with the MacOS X backend. I
>> was wondering whether people here have any tips on speeding things up?
>>
>> As far as I can figure out, this is slow because both the slider and
>> the callback function call ``fig.canvas.draw``. Slider calls it before
>> the callback function, so I definitely need to draw things in that
>> function, but I can get a factor of 2x speedup by doing
>>
>> slider.drawon = False
>>
>> which prevents ``canvas.draw()`` being called twice. However, this is
>> still much too slow, so I started to look into using ``draw_artist``
>> to only update elements that need updating, but this requires
>> partially re-implementing the Slider class.
>>
>> As a side note, using ``draw_artist`` also does not work on the MacOS X
>> backend:
>>
>> https://github.com/matplotlib/matplotlib/issues/166
>>
>> but I'm willing to have a solution that wouldn't work on this backend
>> if it was the only way.
>>
>> Does anyone have a clean solution to increasing the frame rate of this
>> example?
>>
>> Thanks!
>> Tom
>>
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