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4  Enhancements to elpres

4.1  Include graphics files

Graphics files/pictures can be included with the includegraphics-command of the graphicx-package. Please be aware that the dimensions of the pages are 128mm 96mm and therefore included graphics are scaled appropriately. A safe way to generate a page with a picture could be (with pict.png as the name of the graphics file):
   \usepackage[pdftex]{graphicx} % (in preamble) 
   ...
   \begin{rsli}
     \centering
     \distance{1}
     \includegraphics[width=0.9\textwidth,%
                      height=0.9\textheight,%
                      keepaspectratio=true]{pict.png}
     \distance{1}
   \end{rsli}

The \includegraphics[]{} comannd requires to select the correct device driver related option (e. g. pdftex or dvips) (documentclass).

4.2  Arrange text and pictures in two (or more) columns

Text and graphics may be arranged in two or more columns with minipage environments:
   \begin{minipage}[b][0.8\textheight][t]{0.5\textwidth}
     \colorbox{white}{%
       \includegraphics[width=0.9\textwidth]{graphics-file.png}}
   \end{minipage}
   \begin{minipage}[b][0.8\textheight][t]{0.48\textwidth}
   \footnotesize
   \begin{citemize}
      \item ...
      \item ...
      ...
   \end{citemize}
   \end{minipage}

Details on the minipage environment may be found in the LATEX documentation.

4.3  Incremental slides (overlays)

If the contents of slides are to be made visible step by step this can be achieved by a series of output PDF or (PS) files (carrying the same page number) usually called overlays. It may also be of interest to change a highlighting color in a series of overlays. This is most easily done by using the overlays package written by Andreas Nolda together with elpres.
To generate a series of four overlays sequentially showing four lines of a list:
  1. load the overlays package in the preamble
  2. put a psli or rsli slide environment into an overlays (or fragileoverlays) environment
  3. enter the number of overlays as the first parameter to the overlays environment
  4. enter text contents with the visible command with the range of overlays showing this text content
A simple example:
   % to be added in preamble
   \usepackage{overlays}
   ...
   \begin{overlays}{4}
   \begin{psli}[Title of slide]
   \begin{itemize}
     \visible{1-4}{\item first item of list} 
     \visible{2-4}{\item second list item}
     \visible{3-4}{\item 3rd list item}
     \visible{4}{\item final list item}
   \end{itemize}
   \end{psli}
   \end{overlays}
   ... 

The following example uses the alert command to highlight lines sequentially:
   \begin{overlays}{4}
   \begin{psli}[Title of slide]
   \begin{itemize}
     \alert{1}{\item first item of list} 
     \alert{2}{\item second list item}
     \alert{3}{\item 3rd list item}
     \alert{4}{\item final list item}
   \end{itemize}
   \end{psli}
   \end{overlays}

The "hidden" text contents are written by overlays in the same color as the background, default is white. If you use a different background color, you have to change the color of the hidden text as well by assigning the background color to the color name background (understood by the overlays package). In the following example you define a light yellow as background:
   % (in the preamble)
   \definecolor{myyellow}{rgb}{0.96,0.98,0.72} % define color
   \definecolor{background}{named}{myyellow}   % color assigned to 
                                               % hidden text
   \pagecolor{myyellow}                        % color of slide background

For more details on overlays, see the documentation of the package.

4.4  Create a "handout" from a presentation

If you wish to generate a handout from your presentation with more than one pages on a printed page, you may process a PDF presentation file with pdfjam5.
The following command:
   pdfjam --nup 2x3 --scale 0.9 -o new.pdf  presentation.pdf '1-4,7-17,22'

creates a "handout" PDF document (new.pdf) with the slides 1-4,7-17 and 22 of presentation.pdf arranged in two columns and three rows. With the additional option -frame true, pdfjam draws a box around each slide. More details can be found in the pdfjam man page. On Windows systems Acrobat reader may be helpful to print handout documents with more than one slide per printed page.

4.5  Create presentations with hypertext elements

You may use the hyperref package. As you normally will not insert \section{}-like commands, it is easier to define links with
   \hypertarget{target-name}{text}

which can be addressed by
   \hyperlink{target-name}{text}

The hyperref package will produce a warning message, if you use the titlepage-environment (this is inherited from the article class). To avoid the warning you can use the rsli-environment for the titlepage and use \thispagestyle{empty} to suppress the page number on the title.

4.6  Fill background of a presentation with bitmaps

4.6.1  Wallpaper package

To create a slide background with a graphical wallpaper background using bitmap files you may use the wallpaper package6. Load the wallpaper package with
   \usepackage{wallpaper}

in the preamble. In order to generate a background based on bitmap file background.png, enter
   \CenterWallPaper{1}{background.png}

before the contents of the presentation7. This works best with bitmaps with an appropriate aspect ratio, in the case of an 4x3 screen format a bitmap picture of 640x480 pixel would fit perfectly. Moreover bitmap files may be used as tiles as described in the wallpaper documentation like
   \TileSquareWallPaper{4}{background.png}

More details on this topic may be found in the wallpaper documentation.

4.6.2  Eso-pic package

Another package which allows you to paint the background with a picture is eso-pic8:
   \usepackage{eso-pic}
   
   ...

   \AddToShipoutPicture{
   \includegraphics[height=\paperheight]{background.png}
   }

\AddToShipoutPicture{} puts the picture on every page, \AddToShipoutPicture*{} puts it on to the current page, \ClearShipoutPicture clears the background beginning with the current page. Details of eso-pic's commands can be found in the documentation.

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