diff --git a/functions/image.xml b/functions/image.xml
index db9191fa59..dbf2a44249 100644
--- a/functions/image.xml
+++ b/functions/image.xml
@@ -1,5 +1,5 @@
 <?xml encoding="iso-8859-1"?>
-<!-- $Revision: 1.57 $ -->
+<!-- $Revision: 1.58 $ -->
 <reference id="ref.image">
  <title>Image functions</title>
  <titleabbrev>Image</titleabbrev>
@@ -1730,11 +1730,16 @@ ImagePng($im);
      0 (worst quality, smaller file) to 100 (best quality, biggest file).
      Default is to 100.
     </para>
+    <para>
+     If you want to output Progressive JPEGs, you need to set interlacing
+     on with the <function>ImageInterlace</function>.
+    </para>
     <para>
      See also 
      <function>ImagePNG</function>,
      <function>ImageGIF</function>,
-     <function>ImageWBMP</function> and
+     <function>ImageWBMP</function>,
+     <function>ImageInterlace</funtion> and
      <function>ImageTypes</function>.
     </para>
    </refsect1>
@@ -1804,7 +1809,11 @@ ImagePng($im);
      is 0 the interlace bit is turned off.
     </para>
     <para>
-     This functions returns whether the interlace bit is set for the
+     If the interlace bit is set and the image is used as a JPEG image,
+     the image is created as a progressive JPEG. 
+    </para>
+    <para>
+     This function returns whether the interlace bit is set for the
      image.
     </para>
    </refsect1>