<p>Mapnik (and renderd) both support a <code>buffer-size</code> parameter for this purpose.</p>

<p><a href="https://github.com/mapnik/mapnik/wiki/XMLConfigReference">https://github.com/mapnik/mapnik/wiki/XMLConfigReference</a></p>

<p>How does your <code>bleed</code> compare with the built-in <code>buffer-size</code>? I can see one change, which is that you can alter the x and y bleeds independently, but perhaps this should instead be ported upstream to Mapnik?</p>

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