[gimp-help-2] Improved concepts.xml

[Julien Hardlin <jhardlin src gnome org>]

commit 164c47c119d051ee641a009a501318dd363f734a
Author: Michael Grosberg <grosberg michael gmail com>
Date:   Sat Feb 26 08:59:29 2011 +0100

    Improved concepts.xml

 src/concepts/concepts.xml |   98 ++++++++++++++++++++++++++++++---------------
 1 files changed, 65 insertions(+), 33 deletions(-)
---
diff --git a/src/concepts/concepts.xml b/src/concepts/concepts.xml
index 6ba9478..2173fc4 100644
--- a/src/concepts/concepts.xml
+++ b/src/concepts/concepts.xml
@@ -2,16 +2,13 @@
 <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
                        "http://www.docbook.org/xml/4.3/docbookx.dtd";>
 <!-- section history:
+  2011-02-26 Michael added "resolution" and improved "layers"
   2009-03-20 j.h: fixed bug #557343
-  2008-06-03 prokoudine: yet another shot at Russian content
-  2007-02-27 prokoudine: fixes to Russian translation
   2007-02-27 lexa: reorganized concepts
-  2006-05-02 Dust: added Korean translation
-  2006-02-27 kolbjørn: added norwegian
-  2006-01-07 HdJ: Added quote and acronym tags, added english and dutch
+  2006-01-07 HdJ: Added quote and acronym tags, added English and Dutch
              version of layers explanation
-  2005-12-18 Lexa: reviewed and added de translation
--->
+  2005-12-18 Lexa: reviewed and added de translation-->
+  
 <sect1 xmlns:xi="http://www.w3.org/2001/XInclude"; id="gimp-concepts-basic">
   <title>Basic Concepts</title>
 
@@ -48,24 +45,23 @@
       <term>Images</term>
       <listitem>
         <para>
-          Images are the basic entities used by <acronym>GIMP</acronym>.
-          Roughly speaking, an <quote>image</quote> corresponds to a
-          single file, such as a TIFF or JPEG file. You can also think of an
-          image as corresponding to a single display window, but this is not
-          quite correct: it is possible to have multiple windows all
-          displaying the same image. It is not possible to have a single
-          window display more than one image, though, or for an image to have
-          no window displaying it.
+	  Images are the basic entities used by <acronym>GIMP</acronym>. 
+	  Roughly speaking, an <quote>image</quote> corresponds to a single 
+	  file, such as a TIFF or JPEG file. You can also think of an image 
+	  as corresponding to a single display window (although in truth it 
+	  is possible to have multiple windows all displaying the same image). 
+	  It is not possible to have a single window display more than one 
+	  image, though, or for an image to have no window displaying it. 
         </para>
         <para>
-          A <acronym>GIMP</acronym> image may be quite a complicated thing.
-          Instead of thinking of it as something like a sheet of paper with a
-          picture on it, think of it as more like a book, whose
-          pages are called <quote>layers</quote>. In addition to a stack of
-          layers, a <acronym>GIMP</acronym> image may contain a selection
-          mask, a set of channels, and a set of paths. In fact,
-          <acronym>GIMP</acronym> provides a mechanism for attaching arbitrary
-          pieces of data, called <quote>parasites</quote>, to an image.
+	  A <acronym>GIMP</acronym> image may be quite a complicated thing. 
+	  Instead of thinking of it as a sheet of paper with a 
+	  picture on it, think of it as more like a stack of sheets, called 
+	  <quote>layers</quote>. In addition to a stack of layers, a 
+	  <acronym>GIMP</acronym> image may contain a selection mask, a set of 
+	  channels, and a set of paths. In fact, <acronym>GIMP</acronym> 
+	  provides a mechanism for attaching arbitrary pieces of data, called 
+	  <quote>parasites</quote>, to an image. 
         </para>
         <para>
           In <acronym>GIMP</acronym>, it is possible to have many images open
@@ -79,21 +75,57 @@
       </listitem>
     </varlistentry>
     <varlistentry>
-      <term>Layers</term>
+      <term>Layers</term><!--Modified 2011-02-26-->
       <listitem>
         <para>
-          If an image is like a book, then a layer is like a page within the
-          book. The simplest images contain only a single layer, and can be
-          treated like single sheets of paper. Sophisticated
-          <acronym>GIMP</acronym> users often deal with images containing
-          many layers, even dozens of them.  Layers need not be opaque, and
-          they need not cover the entire extent of an image, so when you
-          look at an image's display, you may see more than just the top
-          layer: you may see elements of many layers.
+	  If a simple image can be compared to a single sheet of paper, an 
+	  image with layers is likened to a sheaf of transparent papers 
+	  stacked one on top of the other. You can draw on each paper, but 
+	  still see the content of the other sheets through the transparent 
+	  areas. You can also move one sheet in relation to the others. 
+	  Sophisticated <acronym>GIMP</acronym> users often deal with images 
+	  containing many layers, even dozens of them. Layers need not be 
+	  opaque, and they need not cover the entire extent of an image, so 
+	  when you look at an image's display, you may see more than just the 
+	  top layer: you may see elements of many layers. 
         </para>
       </listitem>
     </varlistentry>
-    <varlistentry id="gimp-concepts-channels" xreflabel="Channels">
+    <varlistentry>
+      <term>
+        <phrase>Resolution</phrase><!--Added 2011-02-26-->
+	<indexterm>
+	  <primary>Resolution</primary>
+	</indexterm>
+      </term>
+      <listitem>
+        <para>
+	  Digital images comprise of a grid of square elements of varying 
+	  colors, called pixels. Each image has a pixel size, such as 900 
+	  pixels wide by 600 pixels high. But pixels don't have a set size 
+	  in physical space. To set up an image for printing, we use a value 
+	  called resolution, defined as the ratio between an image's size in 
+	  pixels and its physical size (usually in inches) when it is printed 
+	  on paper. Most file formats (but not all) can save this value, which 
+	  is expressed as ppi - pixels per inch. When printing a file, the 
+	  resolution value determines the size the image will have on paper, 
+	  and as a result, the physical size of the pixels. The same 900X600 
+	  pixel image may be printed as a small 2X3" card with barely 
+	  noticeable pixels - or as a large poster with large, chunky pixels. 
+	  Images imported from cameras and mobile devices tend to have a 
+	  resolution value attached to the file. The value is usually 72 or 
+	  96ppi. It is important to realize that this value is arbitrary and 
+	  was chosen for historic reasons. You can always change the resolution 
+	  value inside <acronym>GIMP</acronym> - this has no effect on the 
+	  actual image pixels. Furthermore, for uses such as displaying images 
+	  on line, on mobile devices, television or video games - in short, 
+	  any use that is not print - the resolution value is meaningless and 
+	  is ignored, and instead the image is usually displayed so that each 
+	  image pixel conforms to one screen pixel. 
+        </para>
+      </listitem>
+    </varlistentry>
+   <varlistentry id="gimp-concepts-channels" xreflabel="Channels">
       <term>
         <phrase>Channels</phrase>
         <indexterm>