Re: [Matplotlib-users] Problems with rasterizing multiple elements

[Jae-Joon L. <lee...@gm...>]

I recommend you to use LineCollection as it is rasterized as a single image.

For example,

from matplotlib.collections import LineCollection
d = [np.array([ts[0], ys1]).T for ys1 in ys]

lc = LineCollection(d, color='r', lw=0.5, alpha=0.5,
                    rasterized=True)
ax.add_collection(lc)


ax.set_xlim(0, 7)
ax.set_ylim(-1, 1)


If you need to stick to plot command somehow, you need to create your
own artist.
There is a similar example,

http://matplotlib.sourceforge.net/examples/pylab_examples/demo_agg_filter.html

Take a look at the FilteredArtistList class. Your draw method should
be something like

    def draw(self, renderer):
        renderer.start_rasterizing()
        for a in self._artist_list:
            a.draw(renderer)
        renderer.stop_rasterizing()


IHTH,

-JJ


On Wed, Aug 22, 2012 at 2:45 AM, Peter St. John <pet...@gm...> wrote:
> Hi Everyone,
>
> I'm having problems when rasterizing many lines in a plot using the
> rasterized=True keyword using the pdf output.
> Some version info:
> matplotlib version 1.1.1rc
> ubuntu 12.04
> python 2.7.3
>
>
> Here's a basic example that demonstrates my problem:
> # Import matplotlib to create a pdf document
> import matplotlib
> matplotlib.use('Agg')
> from matplotlib.backends.backend_pdf import PdfPages
> pdf = PdfPages('rasterized_test.pdf')
>
> import matplotlib.pylab as plt
>
> # some test data
> import numpy as np
> ts = np.linspace(0,2*np.pi,100) * np.ones((200,100))
> ts += (np.linspace(0, np.pi, 200)[np.newaxis] * np.ones((100,200))).T
> ys = np.sin(ts)
>
> fig = plt.figure()
> ax = fig.add_subplot(111)
> ax.plot(ts[0], ys.T, color='r', lw=0.5, alpha=0.5, rasterized=True)
> pdf.savefig()
>
> pdf.close()
>
>
>
> Essentially, I have a lot (200 in this case) of closely overlapping lines
> which makes the resulting figure (not rasterized) overly difficult to load.
> I would like to rasterize these lines, such that the axis labels (and other
> elements of the plot, not shown) remain vectors while the solution
> trajectories are flattened to a single raster background. However, using the
> code above, the image still takes a long time to load since each trajectory
> is independently rasterized, resulting in multiple layers. (If I open the
> resulting pdf with a program like inkscape, I can manipulate each trajectory
> independently.)
>
> Is it possible to flatten all of the rasterized elements into a single
> layer, so the pdf size would be greatly reduced?
>
> Thanks,
> --Peter
>
>
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