SVG过滤管道

演示可能与mpl一起使用的SVG过滤效果。饼图绘制代码借用了pie_demo.py

请注意，过滤效果仅在您的svg渲染器支持时才有效。

SVG过滤管道示例

输出：

  1. Saving 'svg_filter_pie.svg'
  1. import matplotlib.pyplot as plt
  2. from matplotlib.patches import Shadow
  4. # make a square figure and axes
  5. fig1 = plt.figure(1, figsize=(6, 6))
  6. ax = fig1.add_axes([0.1, 0.1, 0.8, 0.8])
  8. labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
  9. fracs = [15, 30, 45, 10]
  11. explode = (0, 0.05, 0, 0)
  13. # We want to draw the shadow for each pie but we will not use "shadow"
  14. # option as it does'n save the references to the shadow patches.
  15. pies = ax.pie(fracs, explode=explode, labels=labels, autopct='%1.1f%%')
  17. for w in pies[0]:
  18.     # set the id with the label.
  19.     w.set_gid(w.get_label())
  21.     # we don't want to draw the edge of the pie
  22.     w.set_ec("none")
  24. for w in pies[0]:
  25.     # create shadow patch
  26.     s = Shadow(w, -0.01, -0.01)
  27.     s.set_gid(w.get_gid() + "_shadow")
  28.     s.set_zorder(w.get_zorder() - 0.1)
  29.     ax.add_patch(s)
  32. # save
  33. from io import BytesIO
  34. f = BytesIO()
  35. plt.savefig(f, format="svg")
  37. import xml.etree.cElementTree as ET
  40. # filter definition for shadow using a gaussian blur
  41. # and lightening effect.
  42. # The lightening filter is copied from http://www.w3.org/TR/SVG/filters.html
  44. # I tested it with Inkscape and Firefox3. "Gaussian blur" is supported
  45. # in both, but the lightening effect only in the Inkscape. Also note
  46. # that, Inkscape's exporting also may not support it.
  48. filter_def = """
  49.   <defs xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink'>
  50.     <filter id='dropshadow' height='1.2' width='1.2'>
  51.       <feGaussianBlur result='blur' stdDeviation='2'/>
  52.     </filter>
  54.     <filter id='MyFilter' filterUnits='objectBoundingBox' x='0' y='0' width='1' height='1'>
  55.       <feGaussianBlur in='SourceAlpha' stdDeviation='4%' result='blur'/>
  56.       <feOffset in='blur' dx='4%' dy='4%' result='offsetBlur'/>
  57.       <feSpecularLighting in='blur' surfaceScale='5' specularConstant='.75'
  58.            specularExponent='20' lighting-color='#bbbbbb' result='specOut'>
  59.         <fePointLight x='-5000%' y='-10000%' z='20000%'/>
  60.       </feSpecularLighting>
  61.       <feComposite in='specOut' in2='SourceAlpha' operator='in' result='specOut'/>
  62.       <feComposite in='SourceGraphic' in2='specOut' operator='arithmetic'
  63.     k1='0' k2='1' k3='1' k4='0'/>
  64.     </filter>
  65.   </defs>
  66. """
  69. tree, xmlid = ET.XMLID(f.getvalue())
  71. # insert the filter definition in the svg dom tree.
  72. tree.insert(0, ET.XML(filter_def))
  74. for i, pie_name in enumerate(labels):
  75.     pie = xmlid[pie_name]
  76.     pie.set("filter", 'url(#MyFilter)')
  78.     shadow = xmlid[pie_name + "_shadow"]
  79.     shadow.set("filter", 'url(#dropshadow)')
  81. fn = "svg_filter_pie.svg"
  82. print("Saving '%s'" % fn)
  83. ET.ElementTree(tree).write(fn)

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