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+% $Header: /cvsroot/latex-beamer/latex-beamer/doc/beamerug-color.tex,v 1.24 2005/10/23 16:55:54 tantau Exp $
+
+% Copyright 2003, 2004 by Till Tantau <tantau@users.sourceforge.net>.
+%
+% This program can be redistributed and/or modified under the terms
+% of the GNU Public License, version 2.
+
+\section{Colors}
+
+\label{section-colors}
+
+\beamer's color management allows you to specify the color of every
+element (like, say, the color of the section entries in a table of
+contents or, say, the color of the subsection entries in a mini table
+of contents in a sidebar). While the system is quite powerful, it is
+not trivial to use. To simplify the usage of the color system, you
+should consider using a predefined color theme, which takes care of
+everything for you.
+
+In the following, color themes are explained first. The rest of the
+section consists of explanations of how the color management works
+internally. You will need to read these sections only if you wish to
+write your own color themes; or if you are quite happy with the
+predefined themes but you absolutely insist that displayed
+mathematical text simply has to be typeset in a lovely pink.
+
+
+
+\subsection{Color Themes}
+
+In order to also show the effect of the different color themes on the
+sidebar, in the following examples the color themes are used together
+with the outer theme |sidebar|.
+
+\subsubsection{Default and Special-Purpose Color Themes}
+
+\begin{colorthemeexample}{default}
+ The |default| color theme is very sober. It installs little special
+ colors and even less backgrounds. The default color theme sets up
+ the default parent relations between the different \beamer-colors.
+
+ The main colors set in the |default| color theme are the following:
+ \begin{itemize}
+ \item
+ |normal text| is black on white.
+ \item
+ |alerted text| is red.
+ \item
+ |example text| is a dark green (green with 50\% black).
+ \item
+ |structure| is set to a light version of MidnightBlue
+ (more precisely, 20\% red, 20\% green, and 70\% blue).
+ \end{itemize}
+ Use this theme for a no-nonsense presentation. Since this theme is
+ loaded by default, you cannot ``reload'' it after having loaded
+ another color theme.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}[\oarg{options}]{structure}
+ The example was created using |\usecolortheme[named=SeaGreen]{structure}|.
+
+ This theme offers a convenient way of changing the color used for
+ structural elements. More precisely, it just changes the foreground
+ of the \beamer-color |structure|. You can also achieve this by
+ directly invoking the function |\setbeamercolor|, but this color
+ theme makes things a bit easier.
+
+ The theme offers several \meta{options}, which can be used to
+ specify the color to be used for structural elements:
+ \begin{itemize}
+ \item
+ \declare{|rgb=|\marg{rgb tuple}} sets the |structure| foreground
+ to the specified red-green-blue tuple. The numbers are given as
+ decimals between 0 and 1. For example, |rgb={0.5,0,0}| yields a
+ dark red.
+ \item
+ \declare{|RGB=|\marg{rgb tuple}} does the same as |rgb|, except
+ that the numbers range between 0 and 255. For example,
+ |RGB={128,0,0}| yields a dark red.
+ \item
+ \declare{|cmyk=|\marg{cymk tuple}} sets the |structure| foreground
+ to the specified cyan-magenta-yellow-black tuple. The numbers are
+ given as decimals between 0 and 1. For example, |cymk={0,1,1,0.5}|
+ yields a dark red.
+ \item
+ \declare{|cmy=|\marg{cym tuple}} is similar to |cmyk|, except that
+ the black component is not specified.
+ \item
+ \declare{|hsb=|\marg{hsb tuple}} sets the |structure| foreground
+ to the specified hue-saturation-brightness tuple. The numbers are
+ given as decimals between 0 and 1. For example, |hsb={0,1,.5}|
+ yields a dark red.
+ \item
+ \declare{|named=|\marg{color name}} sets the |structure| foreground
+ to a named color. This color must previously have been defined
+ using the |\DefineNamedColor| command. Adding the class option
+ |xcolor=dvipsnames| will install a long list of standard
+ names. See the file |dvipsnam.def| for the list.
+ \end{itemize}
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{sidebartab}
+ This theme changes the colors in a sidebar such that the current
+ entry in a table of contents shown there gets hilighted by showing a
+ different background behind it.
+\end{colorthemeexample}
+
+
+
+\subsubsection{Complete Color Themes}
+
+A ``complete'' color theme is a color theme that completely specifies
+all colors for all parts of a frame. It installs specific colors and
+does not derive the colors from, say, the |structure| \beamer-color.
+Complete color themes happen to have names of flying animals.
+
+\begin{colorthemeexample}{albatross}
+ The color theme is a ``dark'' or ``inverted'' theme using yellow on
+ blue as the main colors. The color theme also installs a slightly
+ darker background color for blocks, which is necessary for
+ presentation themes that use shadows, but which (in my opinion) is
+ undesirable for all other presentation themes. By using the |lily|
+ color theme together with this theme, the backgrounds for blocks can
+ be removed.
+
+ When using a light-on-dark theme like this one, be aware that there
+ are certain disadvantages:
+ \begin{itemize}
+ \item
+ If the room in which the talk is given has been ``darkened,''
+ using such a theme makes it more difficult for the audience to
+ take or read notes.
+ \item
+ Since the room becomes darker, the pupil becomes larger, thus
+ making it harder for the eye to focus. This \emph{can} make text
+ harder to read.
+ \item
+ Printing such slides is difficult at best.
+ \end{itemize}
+
+ On the other hand, a light-on-dark presentation often appears to be
+ more ``stylish'' than a plain black-on-white one.
+
+ The following \meta{options} may be given:
+ \begin{itemize}
+ \item \declare{|overlystylish|} installs a background canvas that
+ is, in my opinion, way too stylish. But then, I do not want
+ to press my taste on other people. When using this option, it is
+ probably a very good idea to also use the |lily| color theme.
+ \end{itemize}
+
+ \example The |overlystylish| option together with the |lily| color theme:
+ \genericthemeexample{colorthemealbatrossstylish}
+\end{colorthemeexample}
+
+
+\begin{colorthemeexample}{beetle}
+ The main ``theme behing this theme'' is to use white and black text
+ on gray background. The white text is used for special emphasis, the
+ black text for normal text. The ``outer stuff'' like the headline
+ and the footline use, however, a bluish color. To change this color,
+ change the background of |palette primary|.
+
+ Great care must be taken with this theme since both the white/gray
+ and the black/gray contrasts are much lower than with other
+ themes. Make sure that the contrast is high enough for the actual
+ presentation.
+
+ You can change the ``grayish'' background by changing the background
+ of |normal text|.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{crane}
+ This theme uses the colors of the Lufthansa, whose logo is a
+ crane. It is \emph{not} an official theme by that company, however.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{dove}
+ This theme is nearly a black and white theme and useful for creating
+ presentations that are easy to print on a black-and-white
+ printer. The theme uses grayscale in certain unavoidable cases, but
+ never color. It also changes the font of alerted text to boldface.
+
+ When using this theme, you should consider using the class option
+ |gray|, which ensures that all colors are converted to
+ grayscale. Also consider using the |structurebold| font theme.
+\end{colorthemeexample}
+
+
+\begin{colorthemeexample}{fly}
+ This theme is the ``consequent'' version of |beetle| and uses
+ white/black/gray throughout. It does not go particularly well with
+ themes that use shadows.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{seagull}
+ Like the |dove| color theme, this theme is useful for printing on a
+ black-and-white printer. However, it uses different shades of gray
+ extensively, which may or may not look good on a transparency.
+\end{colorthemeexample}
+
+
+\begin{colorthemeexample}{wolverine}
+ The theme is based on the colors of the University of Michigan's
+ mascot, a wolverine.
+
+ \themeauthor Madhusudan Singh.
+\end{colorthemeexample}
+
+
+\begin{colorthemeexample}{beaver}
+ The theme is based on the colors of the MIT's mascot, a beaver.
+
+ \themeauthor Madhusudan Singh.
+\end{colorthemeexample}
+
+
+\subsubsection{Inner Color Themes}
+
+Inner color themes only specify the colors of elements used in inner
+themes. Most noticably, they specify the colors used for blocks. They can
+be used together with other (color) themes. If they are used to change the
+inner colors installed by a presentation theme or another color theme,
+they should obviously be specified \emph{after} the other theme has
+been loaded. Inner color themes happen to have flower names.
+
+\begin{colorthemeexample}{lily}
+ This theme is mainly used to \emph{uninstall} any block colors setup
+ by another theme, restoring the colors used in the |default|
+ theme. In particular, using this theme will remove all background
+ colors for blocks.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{orchid}
+ This theme installs white-on-dark block titles. The background of
+ the title of a normal block is set to the foreground of the
+ structure color, the foreground is set to white. The background of
+ alerted blocks are set to red and of example blocks to green. The
+ body of blocks get a nearly transparent background.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{rose}
+ This theme installs nearly transparent backgrounds for both block
+ titles and block bodies. This theme is much less ``aggressive'' than
+ the |orchid| theme. The background colors are derived from the
+ foreground of the structure \beamer-color.
+\end{colorthemeexample}
+
+
+\subsubsection{Outer Color Themes}
+
+An outer color theme changes the palette colors, on which the colors
+used in the headline, footline, and sidebar
+are based by default. Outer color themes normally do not change the
+color of inner elements, except possibly for |titlelike|. They have
+happen to sea-animal names.
+
+\begin{colorthemeexample}{whale}
+ Installs a white-on-dark palette for the headline, footline, and
+ sidebar. The backgrounds used there are set to shades between the
+ structure \beamer-color and black. The foreground is set to
+ white.
+
+ While this color theme can appear to be aggressive, you should note
+ that a dark bar at the border of a frame will have a somewhat
+ different appearance during a presentation than it has on paper:
+ During a presentation the projection on the
+ wall is usually surrounded by blackness. Thus, a dark bar will
+ not create a contrast as opposed to the way it does on
+ paper. Indeed, using this theme will cause the main part of the
+ frame to be more at the focus of attention.
+
+ The counterpart to the theme with respect to blocks is the |orchid|
+ theme. However, pairing it with the |rose| color theme is also
+ interesting.
+\end{colorthemeexample}
+
+\begin{colorthemeexample}{seahorse}
+ Installs a near-transparent backgrounds for the headline, footline,
+ and sidebar. Using this theme will cause navigational elements to be
+ much less ``dominant'' than when using the |whale| theme (see the
+ discussion on contrast there, though).
+
+ It goes well with the |rose| or the |lily| color theme. Pairing it
+ with the |orchid| overemphasizes blocks (in my opinion).
+\end{colorthemeexample}
+
+
+\begin{colorthemeexample}{dolphin}
+ A color theme somewhere in the middle between the whale and the
+ seahorse. It was graciously donated by Manuel Carro. Like the
+ seahorse, it goes well with the |rose| and the |lily| color theme.
+\end{colorthemeexample}
+
+
+
+
+\subsection{Changing the Colors Used for Different Elements of a Presentation}
+
+This section explains how \beamer's color management works.
+
+
+
+\subsubsection{Overview of Beamer's Color Management}
+
+In \beamer's philosophy, every element of a presentation can have a
+different color. Unfortunately, it turned out that simply assigning a
+single color to every element of a presentation is not such a good
+idea. First of all, we sometimes want colors of elements to change
+during a presentation, like the color of the item indicators when they
+become alerted or inside an example block. Second, some elements
+naturally have two colors, namely a foreground and a background, but
+not always. Third, sometimes element somehow should not have any
+special color but should simply ``run along'' with the color of their
+surrounding. Finally, giving a special color to every element makes it
+very hard to globally change colors (like changing all the different
+kind-of-blue things into kind-of-red things) and it makes later
+extensions even harder.
+
+For all these reasons, the color of an element in \beamer\ is a
+structured object, which I call a \emph{\beamer-color}. Every
+\beamer-color has two parts: a foreground and a background. Either of
+these may be ``empty,'' which means that whatever foreground or
+background was active before should remain active when the color is
+used.
+
+\beamer-colors can \emph{inherit} from other \beamer-colors and the
+default themes make extensive use of this feature. For example, there
+is a \beamer-color called |structure| and all sorts of elements
+inherit from this color. Thus, if someone changes |structure|, the
+color of all these elements automatically change accordingly. When a
+color inherits from another color, it can nevertheless still override
+only the foreground or the background.
+
+It is also possible to ``inherit'' from another \beamer-color in a more
+sophisticated way, which is more like \emph{using} the other
+\beamer-color in an indirect way. You can specify that, say, the
+background of the title should be a 90\% of the background of normal
+text and 10\% of the foreground of |structure|.
+
+Inheritance and using of other \beamer-colors is done
+dynamically. This means that if one of the parent \beamer-colors
+changes during the presentation, the derived colors automatically also
+change.
+
+The default color theme, which is always loaded, installs numerous
+\beamer-colors and inheritance relations between them. These colors
+are explained throughout this guide. The color used for, say,
+frametitles is discussed in the section on frametitles, and so on.
+
+
+\subsubsection{Using Beamer's Colors}
+
+A \beamer-color is not a normal color as defined by the |color| and
+|xcolor| packages and, accordingly, cannot be used directly as in
+commands like |\color| or |\colorlet|. Instead, in order to use a
+\beamer-color, you should first call the command |\usebeamercolor|,
+which is explained below. This command will setup two (normal) colors
+called |fg| (for foreground) and |bg| (for, well, guess what). You can
+then say |\color{fg}| to install the foreground color and
+|\color{bg}| to install the background color. You can also use the
+colors |fg| and |bg| in any context in which you normally use a color
+like, say, |red|. If a \beamer-color does not have a foreground or a
+background, the colors |fg| or |bg| (or both) remain unchanged.
+
+Inside templates, this command will typically have already been called
+for you with the option |[fg]|.
+
+\begin{command}{\usebeamercolor\opt{|*|}\oarg{fg or
+ bg}\marg{beamer-color name}}
+ This command (possibly) changes the two colors |fg| and |bg| to the
+ foreground and background color of the \meta{beamer-color name}. If
+ the \beamer-color does not specify a foreground, |fg| is left
+ unchanged; if does not specify a background, |bg| is left
+ unchanged.
+
+ You will often wish to directly use the color |fg| or |bg| after
+ using this command. For this common situation, the optional argument
+ \meta{fg or bg} is useful, which may be either |fg| or
+ |bg|. Giving this option will cause the foreground |fg| or the
+ background |bg| to be immediately installed after they have been
+ setup. Thus, the following command
+\begin{verbatim}
+\usebeamercolor[fg]{normal text}
+\end{verbatim}
+ is a shortcut for
+\begin{verbatim}
+\usebeamercolor{normal text}
+\color{fg}
+\end{verbatim}
+
+ If you use the starred version of this command, the \beamer-color
+ |normal text| is used before the command is invoked. This ensures
+ that, barring evil trickery, the colors |fg| and |bg| will be setup
+ independently of whatever colors happened to be in use when the
+ command is invoked.
+
+ This command has special side-effects. First, the (normal) color
+ |parent.bg| is set to the value of |bg| prior to this call. Thus you
+ can access the color that was in use prior to the call of this
+ command via the color |parent.bg|.
+
+ Second, the special color \meta{beamer-color name}|.fg| is \emph{globally}
+ set to the same value as |fg| and \meta{beamer-color name}|.bg| is
+ globally set to the value of |bg|. This allows you to access the
+ foreground or background of a certain \meta{beamer-color name} after
+ another \beamer-color has been used. However, referring to these
+ special global colors should be kept to the unavoidable minimum and
+ should be done as locally as possible since a change of the
+ \beamer-color will not reflect in a change of the colors
+ \meta{beamer-color name}|.fg| and \meta{beamer-color name}|.bg|
+ until the next invocation of |\usebeamercolor|. Also, if the
+ \meta{beamer-color name} does not specify a foreground or a
+ background color, then the values of the special colors are whatever
+ happened to be the foreground or background at the time of the last
+ invocation of |\usebeamercolor|.
+
+ So, try not to get into the habit of writing |\color{structure.fg}|
+ all the time, at least not without a |\usebeamercolor{structure}|
+ close by.
+
+ \example
+\begin{verbatim}
+ This text is {\usebeamercolor[fg]{alerted text} alerted}. The
+ following box uses the fore- and background of frametitles:
+ {
+ \usebeamercolor[fg]{frametitle}
+ \colorbox{bg}{Frame Title}
+ }
+\end{verbatim}
+
+ \articlenote
+ This command has no effect in |article| mode.
+\end{command}
+
+
+\begin{command}{\ifbeamercolorempty\oarg{fg or bg}\marg{beamer-color
+ name}\marg{if undefined}\marg{if defined}}
+ This command can be used to check whether the foreground or
+ background of some \meta{beamer-color name} is non-empty. If the
+ foreground or background of \meta{beamer-color name} is defined,
+ \meta{if defined} will be executed, otherwise the \meta{if undefined} code.
+
+ \example
+\begin{verbatim}
+\ifbeamercolorempty[bg]{frametitle}
+{ % ``Transparent background''
+ \usebeamercolor[fg]{frametitle}
+ \insertframetitle
+}
+{ % Opaque background
+ \usebeamercolor[fg]{frametitle}
+ \colorbox{bg}{\insertframetitle}
+}
+\end{verbatim}
+\end{command}
+
+
+
+
+\subsubsection{Setting Beamer's Colors}
+
+To set or to change a \beamer-color, you can use the command
+|\setbeamercolor|.
+
+\begin{command}{\setbeamercolor\opt{|*|}\marg{beamer-color name}\marg{options}}
+ Sets or changes a \beamer-color. The \meta{beamer-color name} should
+ be a reasonably simple text (do not try too much trickery and avoid
+ punctuation symbols), but it may contain spaces. Thus, |normal text|
+ is a valid \meta{beamer-color name} and so is |My Color Number 2|.
+
+ In the most simple case, you just specify a foreground by giving the
+ |fg=| option and, possibly, also a background using the |bg=|
+ option.
+
+ \example |\setbeamercolor{normal text}{fg=black,bg=mylightgrey}|
+ \example |\setbeamercolor{alerted text}{fg=red!80!black}|
+
+ The effect of this command is accumulative, thus the following two
+ commands
+\begin{verbatim}
+\setbeamercolor{section in toc}{fg=blue}
+\setbeamercolor{section in toc}{bg=white}
+\end{verbatim}
+ have the same effect as
+\begin{verbatim}
+\setbeamercolor{section in toc}{fg=blue,bg=white}
+\end{verbatim}
+ Naturally, a second call with the same kind of \meta{option} set to
+ a different value overrides a previous call.
+
+ The starred version first resets everything, thereby ``switching
+ off'' the accumulative effect. Use this starred version to
+ completely reset the definition of some \beamer-color.
+
+ The following \meta{options} may be given:
+ \begin{itemize}
+ \item \declare{|fg=|\meta{color}} sets the foreground color of
+ \meta{beamer-color name} to the given (normal) \meta{color}. The
+ \meta{color} may also be a color expression like |red!50!black|,
+ see the manual of the \textsc{xcolor} package. If \meta{color}
+ is empty, the \meta{beamer-color name} ``has no special
+ foreground'' and when the color is used, the foreground
+ currently in force should not be changed.
+
+ Specifying a foreground this way will override any inherited
+ foreground color.
+ \item \declare{|bg=|\meta{color}} does the same as the |fg|
+ option, but for the background.
+ \item \declare{|parent=|\meta{parent beamer-color(s)}} specifies
+ that \meta{beamer-color name} should inherit from the specified
+ \meta{parent beamer-color(s)}. Any foreground and/or background
+ color set by the parents will also be used when
+ \meta{beamer-color name} is used. If multiple parents specify
+ a foreground, the last one ``wins''; and likewise for the
+ backgrounds.
+
+ \example
+\begin{verbatim}
+\setbeamercolor{father}{fg=red}
+\setbeamercolor{mother}{bg=green}
+\setbeamercolor{child}{parent={father,mother}}
+\begin{beamercolorbox}{child}
+ Terrible red on green text.
+\end{beamercolorbox}
+
+\setbeamercolor{father}{fg=blue}
+\begin{beamercolorbox}{child}
+ Now terrible blue on green text, since parent was changed.
+\end{beamercolorbox}
+\end{verbatim}
+
+ Note that a change of the foreground or background of a parent
+ changes the corresponding foreground or background of the child
+ (unless it is overruled).
+
+ A \beamer-color cannot only have parents, but also grandparents
+ and so on.
+ \item \declare{|use=|\meta{another beamer-color}} is used to
+ make sure that another \beamer-color is setup correctly before the
+ foreground or background color specification are evaluated.
+
+ Suppose you wish the foreground of items to be a mixture
+ of 50\% of the foreground of structural elements and 50\% of the
+ normal foreground color. You could try
+\begin{verbatim}
+\setbeamercolor{item}{fg=structure.fg!50!normal text.fg}
+\end{verbatim}
+ However, this will not necessarily give the desired result: If
+ the \beamer-color |structure| changes, the (normal) color
+ |structure.fg| is not immediately updated. In order to ensure
+ that the normal color |structure.fg| is correct, use the
+ following:
+\begin{verbatim}
+\setbeamercolor{item}{use={structure,normal text},fg=structure.fg!50!normal text.fg}
+\end{verbatim}
+ This will guarantee that the colors |structure.fg| and
+ |normal text.fg| are setup correctly when the foreground of
+ |item| is computed.
+
+ To show the difference, consider the following example:
+\begin{verbatim}
+\setbeamercolor{grandfather}{fg=red}
+\setbeamercolor{grandmother}{bg=white}
+\setbeamercolor{father}{parent={grandfather,grandmother}}
+\setbeamercolor{mother}{fg=black}
+{
+ \usebeamercolor{father}\usebeamercolor{mother}
+ %% Defines father.fg and mother.fg globally
+}
+\setbeamercolor{my color A}{fg=father.fg!50!mother.fg}
+\setbeamercolor{my color B}{use={father,mother},fg=father.fg!50!mother.fg}
+
+{\usebeamercolor[fg]{my color A} dark red text}
+{\usebeamercolor[fg]{my color b} also dark red text}
+
+\setbeamercolor{grandfather}{fg=green}
+
+{\usebeamercolor[fg]{my color A} still dark red text}
+{\usebeamercolor[fg]{my color b} now dark green text}
+\end{verbatim}
+ \end{itemize}
+\end{command}
+
+
+
+
+\subsection{The Color of Mathematical Text}
+
+By default, mathematical text does not have any special color---it
+just inherits the ``surrounding'' color. Some people prefer
+mathematical text to have some special color. Though I do not
+recommend this (I think mathematical text should \emph{not} stand out
+admit the normal text), \beamer\ makes it (reasonably) easy to change
+the color of mathematical text. Simply change the following colors:
+
+\begin{element}{math text}\no\yes\no
+ This color is the parent of |math text inlined| and
+ |math text displayed|. It is empty by default. See those colors for
+ details.
+\end{element}
+
+\begin{element}{math text inlined}\no\yes\no
+ \colorparents{math text}
+ If the foreground of this color is set, inlined mathematical text is
+ typeset using this color. This is done via some |\everymath| hackery
+ and may not work in all cases. If not, you'll have to try to find a
+ way around the problem. The background is currently
+ ignored.
+\end{element}
+
+\begin{element}{math text displayed}\no\yes\no
+ \colorparents{math text}
+ Like |math text inlined|, only for so-called ``displayed''
+ mathematical text. This is mathematical text between |\[| and |\]| or
+ between |$$| and |$$| or inside environments like |equation| or
+ |align|. The setup of this color is somewhat fragile, use at your
+ own risk. The background is currently
+ ignored.
+\end{element}
+
+\begin{element}{normal text in math text}\no\yes\no
+ If the foreground of this color is set, normal text inside
+ mathematical text (which is introduced using the |\text| command)
+ will be typeset using this color. The background is currently
+ ignored.
+\end{element}
+
+
+
+\subsection{The Color Palettes}
+
+When one designs a color theme, one faces the following problem:
+Suppose we want the colors in the headline to gradually change from
+black to, say, blue. Whatever is at the very top of the headline
+should be black, what comes right below it should be dark blue, and at
+the bottom of the headline things should just be blue. Unfortunately,
+different outer themes will put different things at the top. One theme
+might put the author at the top, another theme might put the document
+title there. This makes it impossible to directly assign one of the
+three colors ``black'', ``dark blue,'' and ``blue'' to the different
+elements that are typically rendered in the headline. No matter how we
+assign them, things will look wrong for certain outer themes.
+
+To circumvent this problem, \beamer\ uses a layer of \emph{palette
+colors}. Color themes typically only change these palette colors. For
+example, a color theme might make the \beamer-color |palette primary|
+blue, make |palette secondary| a dark blue, and make |palette tertiary|
+black. Outer themes can now setup things such that whatever they show
+at the top of the headline inherits from |palette tertiary|, what comes
+below inherits from |palette secondary|, and whatever is at the bottom
+inherits from |palette tertiary|. This way, color themes can change the
+way even complicated outer themes look and they can do so
+consistently.
+
+Note that the user can still change the color of every element
+individually, simply by overriding the color(s) of the elements in the
+headline. In a sense, the palette colors are just a ``suggestion'' how
+things should be colored by an outer theme.
+
+In detail, the following palette colors are used by outer themes.
+
+
+\begin{element}{palette primary}\no\yes\no
+ Outer themes (should) base the color of navigational elements and,
+ possibly, also of other elements, on the four palette colors. The
+ ``primary'' palette should be used for the most important
+ navigational elements, which are usually the ones that change most
+ often and hence require the most attention by the audience. The
+ ``secondary'' and ``tertiary'' are less important, the ``quaternary'' one
+ is least important.
+
+ By default, the palette colors do not have a background and the
+ foreground ranges from |structure.fg| to |black|.
+
+ For the sidebar, there is an extra set of palette colors, see
+ |palette sidebar primary|.
+\end{element}
+
+\begin{element}{palette secondary}\no\yes\no
+ See |palette primary|.
+\end{element}
+
+\begin{element}{palette tertiary}\no\yes\no
+ See |palette primary|.
+\end{element}
+
+\begin{element}{palette quaternary}\no\yes\no
+ See |palette primary|.
+\end{element}
+
+\begin{element}{palette sidebar primary}\no\yes\no
+ Similar to |palette primary|, only outer themes (should) base the
+ colors of elements in the sidebar of the four sidebar palette
+ colors.
+\end{element}
+
+\begin{element}{palette sidebar secondary}\no\yes\no
+ See |palette sidebar primary|.
+\end{element}
+
+\begin{element}{palette sidebar tertiary}\no\yes\no
+ See |palette sidebar primary|.
+\end{element}
+
+\begin{element}{palette sidebar quaternary}\no\yes\no
+ See |palette sidebar primary|.
+\end{element}
+
+
+
+\subsection{Miscellaneous Colors}
+
+In this section some ``basic'' colors are listed that do not
+``belong'' to any special commands.
+
+\begin{element}{normal text}\no\yes\yes
+ The color is used for normal text. At the beginning of
+ the document the foreground color is installed as
+ |\normalcolor|. The background of this color is used by the
+ default background canvas for the background of the
+ presentation, see Section~\ref{section-canvas}. The background is
+ also the default value of the normal color |bg|.
+
+ Since the color is the ``root'' of all other \beamer-colors, both a
+ foreground and a background must be installed. In particular, to get
+ a transparent background canvas, make the background of the
+ \beamer-color |background canvas| empty, not the background of this
+ color.
+
+ The \beamer-font currently is not used. In particular, redefining this
+ font will not have any effect. This is likely to change in the future.
+\end{element}
+
+\begin{element}{example text}\no\yes\yes
+ The color/font is used when text is typeset inside an |example|
+ block.
+\end{element}
+
+\begin{element}{titlelike}\no\yes\yes
+ This color/font is a more specialized form of the |structure|
+ color/font. It is the base for all elements that are ``like
+ titles.'' This includes the frame title and subtitle as well as the
+ document title and subtitle.
+\end{element}
+
+\begin{element}{separation line}\no\yes\no
+ The foreground of this color is used for separating lines. If the
+ foreground is empty, no separation line is drawn.
+\end{element}
+
+\begin{element}{upper separation line head}\no\yes\no
+ \colorparents{separation line}
+ Special case for the uppermost separation line in a headline.
+\end{element}
+
+\begin{element}{middle separation line head}\no\yes\no
+ \colorparents{separation line}
+ Special case for the middle separation line in a headline.
+\end{element}
+
+\begin{element}{lower separation line head}\no\yes\no
+ \colorparents{separation line}
+ Special case for the lower separation line in a headline.
+\end{element}
+
+\begin{element}{upper separation line foot}\no\yes\no
+ \colorparents{separation line}
+ Special case for the uppermost separation line in a footline.
+\end{element}
+
+\begin{element}{middle separation line foot}\no\yes\no
+ \colorparents{separation line}
+ Special case for the middle separation line in a footline.
+\end{element}
+
+\begin{element}{lower separation line foot}\no\yes\no
+ \colorparents{separation line}
+ Special case for the lower separation line in a footline.
+\end{element}
+
+
+
+
+\subsection{Transparency Effects}
+\label{section-transparent}
+
+By default, \emph{covered} items are not shown during a
+presentation. Thus if you write |\uncover<2>{Text.}|, the text
+is not shown on any but the second slide. On the other slide, the text
+is not simply printed using the background color -- it is not shown at
+all. This effect is most useful if your background does not have a
+uniform color.
+
+Sometimes however, you might prefer that covered items are not
+completely covered. Rather, you would like them to be shown already in
+a very dim or shaded way. This allows your audience to get a feeling
+for what is yet to come, without getting distracted by it. Also, you
+might wish text that is covered ``once more'' still to be visible to
+some degree.
+
+Ideally, there would be an option to make covered text
+``transparent.'' This would mean that when covered text is shown, it
+would instead be mixed with the background behind it. Unfortunately,
+|pgf| does not support real transparency yet. Instead, transparency is
+created by mixing the color of the object you want to show with the
+current background color (the color |bg|, which has hopefully been
+setup such that it is the average color of the background on which the
+object should be placed). To install this effect, you can use:
+\begin{verbatim}
+\setbeamercovered{transparent}
+\end{verbatim}
+This command allows you to specify in a quite general way how a
+covered item should be rendered. You can even specify different ways
+of rendering the item depending on how long it will take before this
+item is shown or for how long it has already been covered once
+more. The transparency effect will automatically apply to all colors,
+\emph{except} for the colors in images. For images there is a
+workaround, see the documentation of the \pgfname\ package.
+
+\begin{command}{\setbeamercovered\marg{options}}
+ This command offers several different options, the most important of
+ which is |transparent|. All options are internally mapped to the two
+ options |still covered| and |again covered|.
+
+ In detail, the following \meta{options} may be given:
+ \begin{itemize}
+ \item \declare{|invisible|} is the default and causes covered text
+ to ``completely disappear.
+ \item \declare{|transparent|}\opt{|=|\meta{opaqueness}} causes
+ covered text to be typset in a ``transparent'' way. By default,
+ this means that 85\% of the background color is mixed into all
+ colors or that the \meta{opaqueness} of the text is 15\%. You can
+ specify a different \meta{percentage}, where |0| means ``totally
+ transparent'' and |100| means ``totally opaque.''
+
+ Unfortunately, this value is kind of ``specific'' to every
+ projector. What looks good on your screen need not look good
+ during a presentation.
+ \item \declare{|dynamic|} Makes all covered text quite transparent,
+ but in a dynamic way. The longer it will take till the text is
+ uncovered, the stronger the transparency.
+ \item \declare{|highly dynamic|} Has the same effect as |dynamic|,
+ but the effect is stronger.
+ \item \declare{|still covered=|\meta{not yet list}} specifies how
+ to render covered items that have not yet been uncovered. The
+ \meta{not yet list} should be a list of |\opaqueness| commands,
+ see the description of that command, below.
+ \example
+\begin{verbatim}
+\setbeamercovered{%
+ still covered={\opaqueness<1>{15}\opaqueness<2>{10}\opaqueness<3>{5}\opaqueness<4->{2}},
+ again covered={\opaqueness<1->{15}}}
+\end{verbatim}
+ \item \declare{|again covered=|\meta{once more list}} specifies how
+ to render covered items that have once more been covered, that is,
+ that had been shown before but are now covered again.
+ \end{itemize}
+\end{command}
+
+\begin{command}{\opaqueness\ssarg{overlay
+ specification}\marg{percentage of opaqueness}}
+ The \meta{overlay specification} specifies on which slides covered
+ text should have which \meta{percentage of opaqueness}. Unlike
+ other overlay specifications, this \meta{overlay specification} is a
+ ``relative'' overlay specification. For example, the specification
+ ``3'' here means ``things that will be uncovered three slides
+ ahead,'' respectively ``things that have once more been covered for
+ three slides.'' More precisely, if an item is uncovered for more
+ than one slide and then covered once more, only the ``first moment
+ of uncovering'' is used for the calculation of how long the item has
+ been covered once more.
+
+ An opaqueness of 100 is fully opaque and 0 is fully
+ transparent. Currently, since real transparency is not yet
+ implemented, this command causes all colors to get a mixing of
+ \meta{percentage of opaqueness} of the current
+ |bg|. At some future point this command might result in real
+ transparency.
+
+ The alternate \pgfname\ extension used inside an opaque area is
+ \meta{percentage of opaqueness}|opaque|. In case of nested calls,
+ only the innermost opaqueness specification is used.
+ \example
+\begin{verbatim}
+\setbeamercovered{still covered={\opaqueness<1->{15}},again covered={\opaqueness<1->{15}}}
+\pgfdeclareimage{book}{book}
+\pgfdeclareimage{book.!15opaque}{filenameforbooknearlytransparent}
+\end{verbatim}
+ Makes everything that is uncovered in two slides only 15 percent
+ opaque.
+\end{command}
+
+
+
+
+
+%%% Local Variables:
+%%% mode: latex
+%%% TeX-master: "beameruserguide"
+%%% End: