So, in the last couple of weeks I tried to look up material about Docbook. I'm still not sure about how you people edit the help files, and I'd obviously prefer a more wysiwg way of doing things, but for now I'll settle for XML-aware editors. I downloaded the repository to my Linux volume but I'm more comfortable working on Windows so I'm using Notepad++ for editing and XMLnotepad to validate the XML. Docbook seems straightforward enough but I do have some questions: what is the significance of adding "acronym" and "quote" tags? what are they for? they seem to have no influence on the final output.
Anyway here is my first change: I took the concepts page and added a much-needed "Resolution" section. I know from experience this is a term that many beginners find difficult to understand, especially when it comes to understanding the resolution property of files coming from digital cameras. I also removed the comparison of a multi-layer image to a book: it is a confusing metaphor as it is nothing like a book in reality, so I changed it to a stack of transparent sheets of paper. Lastly, how important is the way these files are indented? I always use tabs, and any editor I'm familiar with uses tabs to indent lines, while these files seem to use spaces. Is is important to indent the XML in this way? regards Michael
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.docbook.org/xml/4.3/docbookx.dtd"> <!-- section history: 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 version of layers explanation 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> <indexterm> <primary>Concepts</primary> </indexterm> <figure> <title>Wilber, the GIMP mascot</title> <mediaobject> <imageobject> <imagedata format="PNG" fileref="images/using/wilber.png" /> </imageobject> <caption> <para> The Wilber_Construction_Kit (in src/images/) allows you to give the mascot a different appearance. It is the work of Tuomas Kuosmanen (tigertATgimp.org). </para> </caption> </mediaobject> </figure> <para> This section provides a brief introduction to the basic concepts and terminology used in <acronym>GIMP</acronym>. The concepts presented here are explained in much greater depth elsewhere. With a few exceptions, we have avoided cluttering this section with a lot of links and cross-references: everything mentioned here is so high-level that you can easily locate it in the index. </para> <variablelist> <varlistentry> <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 (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 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 at the same time. Although large images may use many megabytes of memory, <acronym>GIMP</acronym> uses a sophisticated tile-based memory management system that allows <acronym>GIMP</acronym> to handle very large images gracefully. There are limits, however, and having more memory available may improve system performance. </para> </listitem> </varlistentry> <varlistentry> <term>Layers</term> <listitem> <para> 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 contant 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> <term>Resolution</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 (usualy 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 physucal size of the pixels. The same 900X600 pixel image may be printed as a small 2X3" card with barely noticable 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 reslution 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> <primary>Channel</primary> </indexterm> </term> <listitem> <!--TRANSLATORS: this is the modified text from glossary.xml, so you should check po/LANG/glossary.po for an old translation--> <para> A Channel is a single component of a pixel's color. For a colored pixel in <acronym>GIMP</acronym>, these components are usually Red, Green, Blue and sometimes transparency (Alpha). For a <link linkend="glossary-graylevel">Grayscale</link> image, they are Gray and Alpha and for an <link linkend="glossary-indexedcolors">Indexed</link> color image, they are Indexed and Alpha. </para> <para> The entire rectangular array of any one of the color components for all of the pixels in an image is also referred to as a Channel. You can see these color channels with the <link linkend="gimp-channel-dialog">Channels dialog</link>. </para> <para> When the image is displayed, <acronym>GIMP</acronym> puts these components together to form the pixel colors for the screen, printer, or other output device. Some output devices may use different channels from Red, Green and Blue. If they do, <acronym>GIMP</acronym>'s channels are converted into the appropriate ones for the device when the image is displayed. </para> <para> Channels can be useful when you are working on an image which needs adjustment in one particular color. For example, if you want to remove <quote>red eye</quote> from a photograph, you might work on the Red channel. </para> <para> You can look at channels as masks which allow or restrict the output of the color that the channel represents. By using Filters on the channel information, you can create many varied and subtle effects on an image. A simple example of using a Filter on the color channels is the <link linkend="plug-in-colors-channel-mixer">Channel Mixer</link> filter. </para> <para> In addition to these channels, <acronym>GIMP</acronym> also allows you to create other channels (or more correctly, Channel Masks), which are displayed in the lower part of the Channels dialog. You can create a <link linkend="gimp-channel-new">New Channel</link> or save a <link linkend="gimp-selection-to-channel">selection to a channel (mask)</link>. See the glossary entry on <link linkend="glossary-masks">Masks</link> for more information about Channel Masks. </para> </listitem> </varlistentry> <varlistentry> <term>Selections</term> <listitem> <para> Often when modify an image, you only want a part of the image to be affected. The <quote>selection</quote> mechanism makes this possible. Each image has its own selection, which you normally see as a moving dashed line separating the selected parts from the unselected parts (the so-called <quote>marching ants</quote> ). Actually this is a bit misleading: selection in <acronym>GIMP</acronym> is graded, not all-or-nothing, and really the selection is represented by a full-fledged grayscale channel. The dashed line that you normally see is simply a contour line at the 50%-selected level. At any time, though, you can visualize the selection channel in all its glorious detail by toggling the <link linkend="gimp-image-window-qmask-button">QuickMask</link> button. </para> <para> A large component of learning how to use <acronym>GIMP</acronym> effectively is acquiring the art of making good selections—selections that contain exactly what you need and nothing more. Because selection-handling is so centrally important, <acronym>GIMP</acronym> provides many tools for doing it: an assortment of selection-making tools, a menu of selection operations, and the ability to switch to Quick Mask mode, in which you can treat the selection channel as though it were a color channel, thereby <quote>painting the selection</quote>. </para> </listitem> </varlistentry> <varlistentry> <term>Undoing</term> <listitem> <para> When you make mistakes, you can undo them. Nearly everything you can do to an image is undoable. In fact, you can usually undo a substantial number of the most recent things you did, if you decide that they were misguided. <acronym>GIMP</acronym> makes this possible by keeping a history of your actions. This history consumes memory, though, so undoability is not infinite. Some actions use very little undo memory, so that you can do dozens of them before the earliest ones are deleted from this history; other types of actions require massive amounts of undo memory. You can configure the amount of memory <acronym>GIMP</acronym> allows for the undo history of each image, but in any situation, you should always be able to undo at least your 2-3 most recent actions. (The most important action that is not undoable is closing an image. For this reason, <acronym>GIMP</acronym> asks you to confirm that you really want to close the image if you have made any changes to it.) </para> </listitem> </varlistentry> <varlistentry> <term>Plug-ins</term> <listitem> <para> Many, probably most, of the things that you do to an image in <acronym>GIMP</acronym> are done by the <acronym>GIMP</acronym> application itself. However, <acronym>GIMP</acronym> also makes extensive use of <quote>plug-ins</quote>, which are external programs that interact very closely with <acronym>GIMP</acronym>, and are capable of manipulating images and other <acronym>GIMP</acronym> objects in very sophisticated ways. Many important plug-ins are bundled with <acronym>GIMP</acronym>, but there are also many available by other means. In fact, writing plug-ins (and scripts) is the easiest way for people not on the <acronym>GIMP</acronym> development team to add new capabilities to <acronym>GIMP</acronym>. </para> <para> All of the commands in the Filters menu, and a substantial number of commands in other menus, are actually implemented as plug-ins. </para> </listitem> </varlistentry> <varlistentry> <term>Scripts</term> <listitem> <para> In addition to plug-ins, which are programs written in the C language, <acronym>GIMP</acronym> can also make use of scripts. The largest number of existing scripts are written in a language called Script-Fu, which is unique to <acronym>GIMP</acronym> (for those who care, it is a dialect of the Lisp-like language called Scheme). It is also possible to write <acronym>GIMP</acronym> scripts in Python or Perl. These languages are more flexible and powerful than Script-Fu; their disadvantage is that they depend on software that does not automatically come packaged with <acronym>GIMP</acronym>, so they are not guaranteed to work correctly in every <acronym>GIMP</acronym> installation. </para> </listitem> </varlistentry> </variablelist> </sect1>
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