[gimp-help] Add patch about export-histogram from Elad Shahar : fix issue #199

[Julien Hardlin <jhardlin src gnome org>]

commit 428aa77d2322d684c9aacdb1462de618ed5fbab5
Author: Julien Hardelin <jhardlin orange fr>
Date:   Tue Jan 7 07:41:40 2020 +0100

    Add patch about export-histogram from Elad Shahar : fix issue #199

 src/menus/colors/info/export-histogram.xml | 115 ++++++++++++++++++++++++++++-
 1 file changed, 113 insertions(+), 2 deletions(-)
---
diff --git a/src/menus/colors/info/export-histogram.xml b/src/menus/colors/info/export-histogram.xml
index 8a7d76ac7..0bc875c43 100644
--- a/src/menus/colors/info/export-histogram.xml
+++ b/src/menus/colors/info/export-histogram.xml
@@ -3,9 +3,120 @@
           "http://www.docbook.org/xml/4.3/docbookx.dtd";>
 <!--section history:
   2018-06-08 j.h Created empty
+  2019-12-20 Elad Shahar - first text version/
 -->
 
-<sect2><!--pas trouvé l'id-->
+<sect2 id="python-fu-histogram-export">
   <title>Export Histogram</title>
-  <para>TODO</para>
+
+  <indexterm>
+    <primary>Colors</primary>
+    <secondary>Export Histogram</secondary>
+  </indexterm>
+  <indexterm>
+    <primary>Export Histogram</primary>
+  </indexterm>
+
+  <sect3>
+    <title>Overview</title>
+    <para>
+      Exports the image histogram to a text file, so it can be used by other programs
+      and loaded into spreadsheets.
+      The histogram is produced for the selected image area. Fully transparent pixels are not counted.
+    </para>
+    <para>
+      The resulting file is a CSV file (Comma Separated Values), which can be imported directly
+      in most spreadsheet programs. The first row of the CSV file is a title row. One data row is
+      generated for each "Bucket". Each pixel value can be in the range of 0 to 255, and will
+      be included in one of the buckets depending on the bucket's range.
+    </para>
+    <para>
+      The first column is titled "Range Start" and contains the starting value of the bucket.
+      The following columns contain the values for different channels. Which channels will
+      be included depends on the image type. The meaning of the values in each of the channel
+      columns, depends on the <guilabel>Output Format</guilabel> option.
+    </para>
+    <figure>
+      <title>Example of file exported by <quote>Export Histogram</quote></title>
+      <screen>
+Range start,   Value,   Red,   Green,   Blue
+          0,     0.0,   0.0,   486.0,    0.0
+          1,     0.0,   0.0,   300.0,    0.0
+          2,     0.0,   0.0,   336.0,    0.0
+          3,     0.0,   0.0,   399.0,    0.0
+          4,     0.0,   0.0,   510.0,    0.0
+          ....
+      </screen>
+    </figure>
+    <para>
+      The example file above was generated for an RGB image, using the
+      <guilabel>Pixel count</guilabel> output format, and a <guilabel>Bucket Size</guilabel> of 1.
+      The row starting with the number 3
+      describes the fourth bucket and will include all pixels from value 3 up to (but not
+      including) value 4. The number 399.0 in that row can then be interpreted as "There
+      are 399 pixels that have a Green value of 3".
+    </para>
+  </sect3>
+
+  <sect3>
+    <title>Activating the filter</title>
+    <para>
+      This filter is found in the image window menu under
+      <menuchoice>
+        <guimenu>Colors</guimenu>
+        <guimenu>Info</guimenu>
+        <guimenuitem>Export Histogram</guimenuitem>
+      </menuchoice>.
+    </para>
+  </sect3>
+
+    <sect3>
+    <title>Options</title>
+    <variablelist>
+      <varlistentry>
+        <term>Histogram File</term>
+        <listitem>
+          <para>
+            The file into which the histogram will be exported.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term>Bucket Size</term>
+        <listitem>
+          <para>
+            The <guilabel>Bucket Size</guilabel> lets you control the number
+            of values considered as similar and counted in the same
+            <quote>bucket</quote>. A higher bucket size will produce less buckets, and thus
+            less rows in the exported file. For example, a Bucket Size of 1 will produced 256
+            buckets, whereas a bucket size of 16 will produce 16 buckets.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term>Sample Average</term>
+        <listitem>
+          <para>
+            If <guilabel>Sample Average</guilabel> is activated, the histogram will be generated
+            for an image obtained by merging all visible layers. Otherwise, the histogram will
+            only consider the current layer.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term>Output Format</term>
+        <listitem>
+          <para>
+            If the <guilabel>Pixel count</guilabel> option is chosen, the values in the generated
+            file will reflect the amount of pixels in each bucket.
+            If <guilabel>Normalized</guilabel> is chosen, the values will be the amount of
+            pixels in the bucket divided by the total amount of pixels.
+            The <guilabel>Percent</guilabel> option is
+            similar to  <guilabel>Normalized</guilabel>, but the values are formatted as percents.
+          </para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+  </sect3>
+
 </sect2>
\ No newline at end of file