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<div class="section" id="misc-example-code-svg-filter-pie-py">
<span id="misc-svg-filter-pie"></span><h1>misc example code: svg_filter_pie.py<a class="headerlink" href="#misc-example-code-svg-filter-pie-py" title="Permalink to this headline">ΒΆ</a></h1>
<p>[<a class="reference external" href="svg_filter_pie.py">source code</a>]</p>
<div class="highlight-python"><div class="highlight"><pre><span class="sd">"""</span>
<span class="sd">Demonstrate SVG filtering effects which might be used with mpl.</span>
<span class="sd">The pie chart drawing code is borrowed from pie_demo.py</span>
<span class="sd">Note that the filtering effects are only effective if your svg rederer</span>
<span class="sd">support it.</span>
<span class="sd">"""</span>
<span class="kn">import</span> <span class="nn">matplotlib</span>
<span class="n">matplotlib</span><span class="o">.</span><span class="n">use</span><span class="p">(</span><span class="s">"Svg"</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="kn">from</span> <span class="nn">matplotlib.patches</span> <span class="kn">import</span> <span class="n">Shadow</span>
<span class="c"># make a square figure and axes</span>
<span class="n">fig1</span> <span class="o">=</span> <span class="n">plt</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">6</span><span class="p">,</span><span class="mi">6</span><span class="p">))</span>
<span class="n">ax</span> <span class="o">=</span> <span class="n">fig1</span><span class="o">.</span><span class="n">add_axes</span><span class="p">([</span><span class="mf">0.1</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">,</span> <span class="mf">0.8</span><span class="p">,</span> <span class="mf">0.8</span><span class="p">])</span>
<span class="n">labels</span> <span class="o">=</span> <span class="s">'Frogs'</span><span class="p">,</span> <span class="s">'Hogs'</span><span class="p">,</span> <span class="s">'Dogs'</span><span class="p">,</span> <span class="s">'Logs'</span>
<span class="n">fracs</span> <span class="o">=</span> <span class="p">[</span><span class="mi">15</span><span class="p">,</span><span class="mi">30</span><span class="p">,</span><span class="mi">45</span><span class="p">,</span> <span class="mi">10</span><span class="p">]</span>
<span class="n">explode</span><span class="o">=</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mf">0.05</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="c"># We want to draw the shadow for each pie but we will not use "shadow"</span>
<span class="c"># option as it does'n save the references to the shadow patches.</span>
<span class="n">pies</span> <span class="o">=</span> <span class="n">ax</span><span class="o">.</span><span class="n">pie</span><span class="p">(</span><span class="n">fracs</span><span class="p">,</span> <span class="n">explode</span><span class="o">=</span><span class="n">explode</span><span class="p">,</span> <span class="n">labels</span><span class="o">=</span><span class="n">labels</span><span class="p">,</span> <span class="n">autopct</span><span class="o">=</span><span class="s">'</span><span class="si">%1.1f%%</span><span class="s">'</span><span class="p">)</span>
<span class="k">for</span> <span class="n">w</span> <span class="ow">in</span> <span class="n">pies</span><span class="p">[</span><span class="mi">0</span><span class="p">]:</span>
<span class="c"># set the id with the label.</span>
<span class="n">w</span><span class="o">.</span><span class="n">set_gid</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">get_label</span><span class="p">())</span>
<span class="c"># we don't want to draw the edge of the pie</span>
<span class="n">w</span><span class="o">.</span><span class="n">set_ec</span><span class="p">(</span><span class="s">"none"</span><span class="p">)</span>
<span class="k">for</span> <span class="n">w</span> <span class="ow">in</span> <span class="n">pies</span><span class="p">[</span><span class="mi">0</span><span class="p">]:</span>
<span class="c"># create shadow patch</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">Shadow</span><span class="p">(</span><span class="n">w</span><span class="p">,</span> <span class="o">-</span><span class="mf">0.01</span><span class="p">,</span> <span class="o">-</span><span class="mf">0.01</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_gid</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">get_gid</span><span class="p">()</span><span class="o">+</span><span class="s">"_shadow"</span><span class="p">)</span>
<span class="n">s</span><span class="o">.</span><span class="n">set_zorder</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">get_zorder</span><span class="p">()</span> <span class="o">-</span> <span class="mf">0.1</span><span class="p">)</span>
<span class="n">ax</span><span class="o">.</span><span class="n">add_patch</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
<span class="c"># save</span>
<span class="kn">from</span> <span class="nn">StringIO</span> <span class="kn">import</span> <span class="n">StringIO</span>
<span class="n">f</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">savefig</span><span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="n">format</span><span class="o">=</span><span class="s">"svg"</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">xml.etree.cElementTree</span> <span class="kn">as</span> <span class="nn">ET</span>
<span class="c"># filter definition for shadow using a gaussian blur</span>
<span class="c"># and lighteneing effect.</span>
<span class="c"># The lightnening filter is copied from http://www.w3.org/TR/SVG/filters.html</span>
<span class="c"># I tested it with Inkscape and Firefox3. "Gaussian blur" is supported</span>
<span class="c"># in both, but the lightnening effect only in the inkscape. Also note</span>
<span class="c"># that, inkscape's exporting also may not support it.</span>
<span class="n">filter_def</span> <span class="o">=</span> <span class="s">"""</span>
<span class="s"> <defs xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink'></span>
<span class="s"> <filter id='dropshadow' height='1.2' width='1.2'></span>
<span class="s"> <feGaussianBlur result='blur' stdDeviation='2'/></span>
<span class="s"> </filter></span>
<span class="s"> <filter id='MyFilter' filterUnits='objectBoundingBox' x='0' y='0' width='1' height='1'></span>
<span class="s"> <feGaussianBlur in='SourceAlpha' stdDeviation='4%' result='blur'/></span>
<span class="s"> <feOffset in='blur' dx='4%' dy='4%' result='offsetBlur'/></span>
<span class="s"> <feSpecularLighting in='blur' surfaceScale='5' specularConstant='.75'</span>
<span class="s"> specularExponent='20' lighting-color='#bbbbbb' result='specOut'></span>
<span class="s"> <fePointLight x='-5000%' y='-10000%' z='20000%'/></span>
<span class="s"> </feSpecularLighting></span>
<span class="s"> <feComposite in='specOut' in2='SourceAlpha' operator='in' result='specOut'/></span>
<span class="s"> <feComposite in='SourceGraphic' in2='specOut' operator='arithmetic'</span>
<span class="s"> k1='0' k2='1' k3='1' k4='0'/></span>
<span class="s"> </filter></span>
<span class="s"> </defs></span>
<span class="s">"""</span>
<span class="n">tree</span><span class="p">,</span> <span class="n">xmlid</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XMLID</span><span class="p">(</span><span class="n">f</span><span class="o">.</span><span class="n">getvalue</span><span class="p">())</span>
<span class="c"># insert the filter definition in the svg dom tree.</span>
<span class="n">tree</span><span class="o">.</span><span class="n">insert</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">ET</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="n">filter_def</span><span class="p">))</span>
<span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">pie_name</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">labels</span><span class="p">):</span>
<span class="n">pie</span> <span class="o">=</span> <span class="n">xmlid</span><span class="p">[</span><span class="n">pie_name</span><span class="p">]</span>
<span class="n">pie</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s">"filter"</span><span class="p">,</span> <span class="s">'url(#MyFilter)'</span><span class="p">)</span>
<span class="n">shadow</span> <span class="o">=</span> <span class="n">xmlid</span><span class="p">[</span><span class="n">pie_name</span> <span class="o">+</span> <span class="s">"_shadow"</span><span class="p">]</span>
<span class="n">shadow</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s">"filter"</span><span class="p">,</span><span class="s">'url(#dropshadow)'</span><span class="p">)</span>
<span class="n">fn</span> <span class="o">=</span> <span class="s">"svg_filter_pie.svg"</span>
<span class="k">print</span> <span class="s">"Saving '</span><span class="si">%s</span><span class="s">'"</span> <span class="o">%</span> <span class="n">fn</span>
<span class="n">ET</span><span class="o">.</span><span class="n">ElementTree</span><span class="p">(</span><span class="n">tree</span><span class="p">)</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">fn</span><span class="p">)</span>
</pre></div>
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