diff --git a/reference/image/constants.xml b/reference/image/constants.xml
index f182cfcfe4..42eab6077d 100644
--- a/reference/image/constants.xml
+++ b/reference/image/constants.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.6 $ -->
+<!-- $Revision: 1.7 $ -->
 <section id="image.constants">
  &reftitle.constants;
  &extension.constants;
@@ -353,6 +353,83 @@
    <listitem>
     <simpara>
      
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_NO_FILTER</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_FILTER_NONE</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_FILTER_SUB</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_FILTER_UP</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_FILTER_AVG</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_FILTER_PAETH</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
+    </simpara>
+   </listitem>
+  </varlistentry>
+  <varlistentry>
+   <term>
+    <constant>PNG_ALL_FILTERS</constant> 
+    (<type>integer</type>)
+   </term>
+   <listitem>
+    <simpara>
+     
     </simpara>
    </listitem>
   </varlistentry>
diff --git a/reference/image/functions/imagepng.xml b/reference/image/functions/imagepng.xml
index c158249404..c20df50f29 100644
--- a/reference/image/functions/imagepng.xml
+++ b/reference/image/functions/imagepng.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.10 $ -->
+<!-- $Revision: 1.11 $ -->
 <refentry id="function.imagepng">
  <refnamediv>
   <refname>imagepng</refname>
@@ -12,6 +12,7 @@
    <methodparam><type>resource</type><parameter>image</parameter></methodparam>
    <methodparam choice="opt"><type>string</type><parameter>filename</parameter></methodparam>
    <methodparam choice="opt"><type>int</type><parameter>quality</parameter></methodparam>
+   <methodparam choice="opt"><type>int</type><parameter>filters</parameter></methodparam>
   </methodsynopsis>
   <para>
    Outputs or saves a <acronym>PNG</acronym> image from the given 
@@ -30,6 +31,12 @@
        The path to the saved file. If not set or &null;, the raw image stream
        will be outputed directly.
       </para>
+      <note>
+       <para>
+        &null; is invalid if the <parameter>quality</parameter> and
+        <parameter>filters</parameter> arguments are not used.
+       </para>
+      </note>
      </listitem>
     </varlistentry>
     <varlistentry>
@@ -40,6 +47,18 @@
       </para>
      </listitem>
     </varlistentry>
+    <varlistentry>
+     <term><parameter>filters</parameter></term>
+     <listitem>
+      <para>
+       Allows reducing the PNG file size. It is a bitmask field which may be
+       set to any combination of the <literal>PNG_FILTER_XXX</literal> 
+       constants. <constant>PNG_NO_FILTER</constant> or 
+       <constant>PNG_ALL_FILTERS</constant> may also be used to respectively
+       disable or activate all filters.
+      </para>
+     </listitem>
+    </varlistentry>
    </variablelist>
   </para>
  </refsect1>
@@ -62,6 +81,12 @@
       </row>
      </thead>
      <tbody>
+      <row>
+       <entry>5.1.3</entry>
+       <entry>
+        Added the <parameter>filters</parameter> parameter.
+       </entry>
+      </row>
       <row>
        <entry>5.1.2</entry>
        <entry>