[gimp-help] Add HEIF file format

[Julien Hardlin <jhardlin src gnome org>]

commit 64cd3adc9edd7917197605997e18286e19c5ae1b
Author: Julien Hardelin <jhardlin orange fr>
Date:   Tue Dec 3 15:18:01 2019 +0100

    Add HEIF file format

 images/C/using/export-heif-dialog.png | Bin 0 -> 14346 bytes
 src/using/fileformats.xml             |  36 +++++++++++++++++++++++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)
---
diff --git a/images/C/using/export-heif-dialog.png b/images/C/using/export-heif-dialog.png
new file mode 100644
index 000000000..79faccfd6
Binary files /dev/null and b/images/C/using/export-heif-dialog.png differ
diff --git a/src/using/fileformats.xml b/src/using/fileformats.xml
index 763dfd949..4f516e193 100644
--- a/src/using/fileformats.xml
+++ b/src/using/fileformats.xml
@@ -3,12 +3,10 @@
                        "http://www.docbook.org/xml/4.3/docbookx.dtd";>
 <!-- section history:
   2015-12-21 j.h: fixed bug #691579: save color values from transparent pixels (PNG)
-  2012-03-23 j.h: update to v2.8
   2007-10-06 ude: added description for "quality settings from original image"
   2007-07-15 lexa: added PackBits description
   2007-03-19 lexa: added description for save dialogs for jpeg gif png and tif
-  2006-07-11 lexa: enhanced docbook compliance
-  2006-02-25 fixed invalid image reference
+
 -->
 <sect1 id="gimp-using-fileformats">
   <title>Files</title>
@@ -259,6 +257,38 @@
         </varlistentry>
       </variablelist>
     </sect3>
+    
+    <sect3 id="file-heif-export">
+      <title>Export Image as HEIF/HEIC</title>
+      <indexterm>
+        <primary>HEIF/HEIC</primary>
+      </indexterm>
+      <para>
+        HEIF stands for High Efficiency Image File Format. Also known as HEIC 
+        High Efficiency Image Coding.
+      </para>
+      <para>
+        Twice as much information can be stored in a HEIF image as in a JPEG 
+        image of the same size, resulting in a better quality. As of 
+        October 2019, no browser supports HEIF natively.
+      </para>
+      <para>
+        More information in <ulink 
+url="http://en.wikipedia/wiki/High_Efficiency_Image_File_Format";>Wikipedia</ulink>.
+      </para>
+      <figure>
+        <title>The HEIF/HEIC Export dialog</title>
+        <mediaobject>
+          <imageobject>
+            <imagedata format="PNG"
+              fileref="images/using/export-heif-dialog.png"/>
+          </imageobject>
+        </mediaobject>
+      </figure>
+      <para>
+        These options are self-explanatory.
+      </para>
+    </sect3>
 
     <sect3 id="file-jpeg-save">
       <title>Export Image as JPEG</title>