[gimp-help] Add symmetric-nearest-neighbor filter. Fix issue #77.

[Julien Hardlin <jhardlin src gnome org>]

commit 4d7d1a2b29b36f3b0f09df5037d8b934abda54b6
Author: Julien Hardelin <jhardlin orange fr>
Date:   Thu Nov 29 18:14:51 2018 +0100

    Add symmetric-nearest-neighbor filter. Fix issue #77.

 images/C/filters/enhance/snn-dialog.png            | Bin 0 -> 17040 bytes
 .../C/filters/examples/enhance/snn-ex-denoise.jpg  | Bin 0 -> 22198 bytes
 images/C/filters/examples/enhance/snn-pairs.jpg    | Bin 0 -> 2685 bytes
 images/C/filters/examples/enhance/snn-radius.jpg   | Bin 0 -> 5703 bytes
 src/filters/enhance.xml                            |   5 +-
 src/filters/enhance/symmetric-nearest-neighbor.xml | 129 +++++++++++++++++++++
 6 files changed, 132 insertions(+), 2 deletions(-)
---
diff --git a/images/C/filters/enhance/snn-dialog.png b/images/C/filters/enhance/snn-dialog.png
new file mode 100644
index 000000000..199c4dcde
Binary files /dev/null and b/images/C/filters/enhance/snn-dialog.png differ
diff --git a/images/C/filters/examples/enhance/snn-ex-denoise.jpg 
b/images/C/filters/examples/enhance/snn-ex-denoise.jpg
new file mode 100644
index 000000000..14adac240
Binary files /dev/null and b/images/C/filters/examples/enhance/snn-ex-denoise.jpg differ
diff --git a/images/C/filters/examples/enhance/snn-pairs.jpg b/images/C/filters/examples/enhance/snn-pairs.jpg
new file mode 100644
index 000000000..7199410d0
Binary files /dev/null and b/images/C/filters/examples/enhance/snn-pairs.jpg differ
diff --git a/images/C/filters/examples/enhance/snn-radius.jpg 
b/images/C/filters/examples/enhance/snn-radius.jpg
new file mode 100644
index 000000000..b1fda3a80
Binary files /dev/null and b/images/C/filters/examples/enhance/snn-radius.jpg differ
diff --git a/src/filters/enhance.xml b/src/filters/enhance.xml
index 0922e32c2..7b60c0ae5 100644
--- a/src/filters/enhance.xml
+++ b/src/filters/enhance.xml
@@ -18,10 +18,11 @@
   <xi:include href="enhance/antialias.xml"/>
   <xi:include href="enhance/deinterlace.xml"/>
   <xi:include href="enhance/high-pass.xml"/>
+  <xi:include href="enhance/red-eye-removal.xml"/>
+  <xi:include href="enhance/symmetric-nearest-neighbor.xml"/>
+  <xi:include href="enhance/unsharp_mask.xml"/>
   <xi:include href="enhance/despeckle.xml"/>
   <xi:include href="enhance/destripe.xml"/>
   <xi:include href="enhance/NL_filter.xml"/>
-  <xi:include href="enhance/red-eye-removal.xml"/>
   <xi:include href="enhance/sharpen.xml"/>
-  <xi:include href="enhance/unsharp_mask.xml"/>
 </sect1>
diff --git a/src/filters/enhance/symmetric-nearest-neighbor.xml 
b/src/filters/enhance/symmetric-nearest-neighbor.xml
new file mode 100644
index 000000000..0963789cb
--- /dev/null
+++ b/src/filters/enhance/symmetric-nearest-neighbor.xml
@@ -0,0 +1,129 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE sect2 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+                       "http://www.docbook.org/xml/4.3/docbookx.dtd";>
+
+<!-- section history:
+  2018-11-25 j.h: Created
+-->
+
+<sect2 id="gimp-filter-snn-mean">
+  <title>Symmetric Nearest Neighbor</title>
+
+  <indexterm>
+    <primary>Filters</primary>
+    <secondary>Enhance</secondary>
+    <tertiary>Symmetric Nearest Neighbor</tertiary>
+  </indexterm>
+  <indexterm>
+    <primary>Symmetric Nearest Neighbor</primary>
+  </indexterm>
+
+  <sect3>
+    <title>Overview</title>
+    <para>
+      This filter blurs the image preserving edges. It is very effective in 
+      noise reduction maintaining sharp edges.
+    </para>
+    <para>
+      It works comparing each pixel to its neighboring pixels and to 1 or 2 
+      <emphasis>pairs</emphasis> of symmetric pixels around the center.
+      <mediaobject>
+        <imageobject>
+          <imagedata 
+            fileref="images/filters/examples/enhance/snn-pairs.jpg"
+            format="JPG"/>
+        </imageobject>
+        <caption>
+          <para>
+            4 symmetric pairs
+          </para>
+        </caption>
+      </mediaobject>
+    </para>
+  </sect3>
+  
+  <sect3>
+    <title>Activating the filter</title>
+    <para>
+      You can find this filter through
+      <menuchoice>
+        <guimenu>Filters</guimenu>
+        <guisubmenu>Enhance</guisubmenu>
+        <guimenuitem>Symmetric Nearest Neighbor…</guimenuitem>
+      </menuchoice>.
+    </para>
+  </sect3>
+  
+  <sect3>
+    <title>Options</title>
+    <figure>
+      <title><quote>Symmetric Nearest neighbor</quote> filter options</title>
+      <mediaobject>
+        <imageobject>
+          <imagedata 
+            fileref="images/filters/enhance/snn-dialog.png"
+            format="PNG"/>
+        </imageobject>
+      </mediaobject>
+    </figure>
+    
+    <variablelist>
+      <varlistentry>
+        <term><guilabel>Presets</guilabel>, <guilabel>Preview</guilabel>, 
+          <guilabel>Split view</guilabel></term>
+        <listitem>
+          <para>
+            These options are common to GEGL-based filters. Please refer to 
+            <xref linkend="gimp-filters-common"/>.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><guilabel>Radius</guilabel></term>
+        <listitem>
+          <para>
+            Radius, in pixels, of square pixel region. Width and height of this 
+            region are <emphasis>radius*2+1</emphasis>:
+            <mediaobject>
+              <imageobject>
+                <imagedata 
+                  fileref="images/filters/examples/enhance/snn-radius.jpg"
+                  format="JPG"/>
+              </imageobject>
+            </mediaobject>
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><guilabel>Pairs</guilabel></term>
+        <listitem>
+          <para>
+            You can select 1 or 2 pairs : higher number preserves more acute 
+            features.
+          </para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+  </sect3>
+
+  <sect3>
+    <title>Example</title>
+    <mediaobject>
+      <imageobject>
+        <imagedata 
+          fileref="images/filters/examples/enhance/snn-ex-denoise.jpg"
+          format="JPG"/>
+      </imageobject>
+      <caption>
+        <para>
+          Left: original..............Right: filter applied
+        </para>
+      </caption>
+    </mediaobject>
+  </sect3>
+</sect2>
+
+
+