matplotlib-users Mailing List for matplotlib

I am trying to rasterize the fancy arrows drawn by the lovely streamplot() function, but am running into major problems since the arrows are drawn at a very late stage (to preserve their aspect ratio).

--------------
from pylab import *
fig = figure(figsize=(10,5))
x = linspace(-1,1,10)[:, None]
x = linspace(-1,1,10)[:, None]
y = x.T

# Why don't the first two work... it is annoying.  Is it a "bug" or a feature?
#s = streamplot(x, y, x+0*y, y+0*x)
#s = streamplot(x.flat, y.flat, x+0*y, y+0*x)
s = streamplot(x.ravel(), y.ravel(), x+0*y, y+0*x,
               density=0.5, arrowstyle='->', arrowsize=2.0)

setp(s.lines, rasterized=True)  # This works fine.
setp(s.arrows, rasterized=True) # This has no effect (bug?)
setp(s.arrows, visible=False)   # This also has no effect (bug?)

# Let's get the patches instead
ax = gca()
#setp(ax.patches, rasterized=True)  # The FancyArrowPatchs are here

# This does not rasterize the arrows, giving multiple warnings:
#    UserWarning: Rasterization of 'FancyArrowPatch(...)' will be ignored
savefig('tst1.pdf') 

# How about rasterizing the whole axis
ax.set_rasterized(True)
savefig('tst2.pdf')     # Weird results! (Bug?) Also rasterizes labels.

savefig('tst.png')      # This works, except that labels rasterized too.
------------

The problem appears to be that FancyArrowPatch objects are transformed late in the game (so that the arrow-heads etc. are in proper proportions), and rasterization seems to need to occur at an earlier stage.  The arrows are in the axes, so there is no upper-level container to rasterize them but not the axes labels etc.  Rasterizing the axes (tst2.pdf) does rasterize the arrows, but also the labels, and does something really wonky with the plot (the streamlines and axis frame are completely unaligned… most definitely a bug, but I need to track down exactly where this broke or if it has been fixed).

Saving to png works, but also rasterizes the labels and ticks which I want to avoid.

Is there a robust way to convert the FancyArrowPatch objects to something not-fancy at some point once I have fixed the size of the axis, figure etc. so that I can then rasterize the appropriate elements only?  Are the other behaviours noted in the comments bugs (in which case I will open some incidents)?

Thanks,
Michael.

ah, should have been:
ax1.grid()
ax2.grid()
ax1.yaxis.grid(False)

Hi Paul,

thanks for your efforts, I've figured it out by myself by now, with you
pieces of code:

ax1.grid()
ax2.grid()
ax1.xaxis.grid(False)

does the trick :)

On Thu, Jun 13, 2013 at 1:33 PM, Daniel Mader <
dan...@go...> wrote:

> Hi Paul,
>
> I've modified your suggestion a little, since I don't want a grid for the
> primary axis at all -- unfortunately to no avail, i.e. no grid line at all:
>
> import numpy
>
> import matplotlib
>
> matplotlib.use('agg')
>
> import matplotlib.pyplot as plt
>
>
> datax = numpy.arange(50)
>
> data1 = numpy.sin(datax)*1.5
>
> data2 = datax**2
>
>
> plt.close('all')
>
>
> fig = plt.figure()
>
> ax1 = fig.add_subplot(111)
>
> ax2 = ax1.twinx()
>
>
> ax1.plot(datax, data1, 'x')
>
> ax2.plot(datax, data2, '--')
>
>
> #for ax in [ax1, ax2]:
>
> # ax.xaxis.grid(True, which='both') # `which` can be 'minor', 'major', or
> 'both'
>
> # ax.yaxis.grid(True, which='both')
>
>
> ax2.xaxis.grid(True, which='both')
>
> ax2.yaxis.grid(True, which='both')
>
>
> fig.savefig('twinxgrid.png')
>
> #fig.show()
>
>
>
Try throwing this in there:

ax1.xaxis.grid(False, which='both')

ax1.yaxis.grid(False, which='both')

On Thu, Jun 13, 2013 at 11:40 PM, Sudheer Joseph
<sud...@ya...>wrote:

> Thank you,
> I don't see a way other than starting in normal mode as the moment I type
> plot command it get displayed and I don't need to do a show command.
>

In the qtconsole, you can enter multi-line mode with crtl+enter.

Thank you,
I don't see a way other than starting in normal mode as the moment I type plot command it get displayed and I don't need to do a show command. 
With best regards sudheer

Thank you Roban,
                     Your that trick worked,
if I keep ts.plot(), savefig('ts.pdf') both on same line it works!

with best regards
Sudheer

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>________________________________
> From: Roban Kramer <ro...@gm...>
>To: sud...@ya... 
>Cc: Paul Hobson <pmh...@gm...>; "mat...@li..." <mat...@li...> 
>Sent: Thursday, 13 June 2013 8:12 PM
>Subject: Re: [Matplotlib-users] savefig
> 
>
>
>savefig works for me when I put both the plotting commands and the savefig call in the *same* code cell.
>
>
>
>On Thu, Jun 13, 2013 at 10:31 AM, Sudheer Joseph <sud...@ya...> wrote:
>
>Thank you,
>>I don't see a way other than starting in normal mode as the moment I type plot command it get displayed and I don't need to do a show command. 
>>With best regards sudheer 
>>
>>
>>
>>________________________________
>> From:  Paul Hobson <pmh...@gm...>; 
>>To:  Sudheer Joseph <sud...@ya...>; 
>>Cc:  mat...@li... <mat...@li...>; 
>>Subject:  Re: [Matplotlib-users] savefig 
>>Sent:  Thu, Jun 13, 2013 2:23:05 PM 
>>
>>
>>
>>
>>
>>On Wed, Jun 12, 2013 at 10:28 PM, Sudheer Joseph <sud...@ya...> wrote:
>>
>>Dear experts,
>>>I start ipython in ipython qtconsole --pylab=inline mode and make a plot. But if I use savefig('fig.png') the figure do not get saved instead I get a blank page.
>>>
>>> I also tried img.save('fig.png',png) but no use. Is there a way out or I need to do this after quitting and restarting in normal mode each time I want to save?
>>>
>>>ipython qtconsole --pylab=inline
>>>
>>>
>>>In [93]: ts.plot()
>>>Out[93]: <matplotlib.axes.AxesSubplot at 0x9135490>
>>>
>>
>>
>>The fig is destroyed after it has been displayed by the console. Try saving it before it gets shown.
>>-p  
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>
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