.. _sphx_glr_gallery_misc_svg_filter_line.py:


===============
SVG Filter Line
===============

Demonstrate SVG filtering effects which might be used with mpl.

Note that the filtering effects are only effective if your svg renderer
support it.




.. image:: /gallery/misc/images/sphx_glr_svg_filter_line_001.png
    :align: center


.. rst-class:: sphx-glr-script-out

 Out::

    Saving 'svg_filter_line.svg'




|


.. code-block:: python


    from __future__ import print_function

    import matplotlib.pyplot as plt
    import matplotlib.transforms as mtransforms

    fig1 = plt.figure()
    ax = fig1.add_axes([0.1, 0.1, 0.8, 0.8])

    # draw lines
    l1, = ax.plot([0.1, 0.5, 0.9], [0.1, 0.9, 0.5], "bo-",
                  mec="b", lw=5, ms=10, label="Line 1")
    l2, = ax.plot([0.1, 0.5, 0.9], [0.5, 0.2, 0.7], "rs-",
                  mec="r", lw=5, ms=10, color="r", label="Line 2")


    for l in [l1, l2]:

        # draw shadows with same lines with slight offset and gray colors.

        xx = l.get_xdata()
        yy = l.get_ydata()
        shadow, = ax.plot(xx, yy)
        shadow.update_from(l)

        # adjust color
        shadow.set_color("0.2")
        # adjust zorder of the shadow lines so that it is drawn below the
        # original lines
        shadow.set_zorder(l.get_zorder() - 0.5)

        # offset transform
        ot = mtransforms.offset_copy(l.get_transform(), fig1,
                                     x=4.0, y=-6.0, units='points')

        shadow.set_transform(ot)

        # set the id for a later use
        shadow.set_gid(l.get_label() + "_shadow")


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

    # save the figure as a bytes string in the svg format.
    from io import BytesIO
    f = BytesIO()
    plt.savefig(f, format="svg")


    import xml.etree.cElementTree as ET

    # filter definition for a gaussian blur
    filter_def = """
      <defs  xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink'>
        <filter id='dropshadow' height='1.2' width='1.2'>
          <feGaussianBlur result='blur' stdDeviation='3'/>
        </filter>
      </defs>
    """


    # read in the saved svg
    tree, xmlid = ET.XMLID(f.getvalue())

    # insert the filter definition in the svg dom tree.
    tree.insert(0, ET.XML(filter_def))

    for l in [l1, l2]:
        # pick up the svg element with given id
        shadow = xmlid[l.get_label() + "_shadow"]
        # apply shadow filter
        shadow.set("filter", 'url(#dropshadow)')

    fn = "svg_filter_line.svg"
    print("Saving '%s'" % fn)
    ET.ElementTree(tree).write(fn)



.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example


  .. container:: binder-badge

    .. image:: https://static.mybinder.org/badge.svg
      :target: https://mybinder.org/v2/gh/choldgraf/matplotlib/gh-pages?filepath=_downloads/svg_filter_line.ipynb
      :width: 150 px


  .. container:: sphx-glr-download

     :download:`Download Python source code: svg_filter_line.py <svg_filter_line.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: svg_filter_line.ipynb <svg_filter_line.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.readthedocs.io>`_