The pipeline
<p:declare-step xmlns:c="http://www.w3.org/ns/xproc-step" xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" name="main" version="3.0">
<p:output port="result" sequence="true"/>
<p:identity name="inline">
<p:with-input port="source">
<p:inline encoding="unknown" content-type="image/png">
iVBORw0KGgoAAAANSUhEUgAAAIAAAAAdCAYAAABixmRWAAAABGdBTUEAALGPC/xhBQAAACBjSFJN
</p:inline>
</p:with-input>
</p:identity>
<p:cast-content-type name="cast" content-type="application/xml">
<p:with-input port="source" pipe="@inline"/>
</p:cast-content-type>
<p:wrap-sequence wrapper="c:result"/>
</p:declare-step>
