Displaying PowerPoint slides

One big driver for this project is a requirement many of us have to be able to use the Internet Tablet to show slides created in Microsoft PowerPoint. This is not to say that the team is in any way anti-OpenOffice.org but many of us have day jobs where we are heavy users of PowerPoint and cannot change that. This page tries to demonstrate how this project can help, if that is the situation you find yourself in.

The best way to achieve this is to generate a high-quality PDF from the slides, render them offline and convert the slides into high quality images and display them directly to the VGA device. This process works for me, although it has some disadvantages, and is described below. There are two other ways to achieve this which are also described:

Creating low resolution images directly from PowerPoint
Using X-windows-based programs to display PDF of the slides

Use high quality images

In my experience this produces the highest quality slide images and the best presentation.

Advantages

The complex processing is done by the (presumably more powerful) Windows or Unix systems running PowerPoint, PrimoPDF, ImageMagick and Ghostscript in rendering the slides: all the tablet needs to do is display the images
Display is quick and simple and it is possible to move forwards and backwards through slides with no delays
The simplicity reduces the risk of the display program crashing on complex slides
The PDF printing process and the conversion process produces high quality images which can be displayed at high resolution.

Disadvantages

The process is quite complex and involves installing and using several software packages. One of these, PrimoPDF, is not open source.
Even on high performance systems both the PDF export and the conversion to JPG can take a long time (several minutes).
The slides I produce do not fill the 1280x1024 screen. Tailoring the slides to get exactly the resolution and size you want can involve complex sets of qualifiers in ImageMagick, possibly including some loss of quality.
It is possible that other configurations may need to specify different ImageMagick qualifiers. I found that the -display 100 option was quite critical to get the required resolution to get high quality images. If larger values of -display are required, you are likely to need to include the -scale qualifier to reduce the image size
The images are tailored to be displayed at a particular resolution. If you find that you need to use a differnet resolution (e.g. due to limitations of the display device) the ImageMagick convert process must be repeated with different qualifiers. This may be impossible to do on-site. For a really critical presentation it may be useful to prepare versions at different resolutions.
As with all PDF-based methods, this involves "printing" the slides which means builds are not displayed.

Brief "How To"

I use the following steps:

Export the slides to a PDF. To do this I use a free (but not open source) program called PrimoPDF. This program installs itself as a printer on your Windows system and can be used to create a PDF of your presentation. I use the "Screen" quality setting.
Convert the PDF to a series of JPG files. To do this I use the (free and open source) ImageMagick. This runs either on Linux or on Windows. You also need a postscript interpreter installed, such as Ghostscript.

The ImageMagick command I use is:
```
convert -density 100 file.pdf file%02d.jpg
```
Copy the files (file*.jpg) to the internet tablet. This could be using scp, or plugging in a memory card or connecting using USB or accessing a Windows share on the network.
Using Xterm, cd to the directory containing the files and display the slides in high resolution using the sisusb-slideshow.sh script:
```
sisusb-slideshow.sh -m 3 file00.jpg
```
You may need to use a different value for the -m option. The sisusb-slideshow.sh script takes the same options as the sisbit program.
The script allows you to display each slide in turn (just press return to display the next slide), go backwards, go to the start, etc. Enter Q to exit the script.

Creating images directly from PowerPoint

PowerPoint can save a complete presentation as a series of images (File->Save As...). These image files can be copied to the tablet and displayed one at a time, directly to the device, using the sisbit program.

Advantages

The complex processing is done by the (presumably more powerful) PowerPoint system in exporting the slides: all the tablet needs to do is display the images
Display is quick and simple and it is possible to move forwards and backwards through slides with no delays
The simplicity reduces the risk of the display program crashing on complex slides

Disadvantages

The image quality PowerPoint produces is quite poor: noticeably lower than can be achieved using PDF.

Brief "How To"

Export the PowerPoint presentation to JPG files using File->Save As.... This will create a set of files called Slide1.JPG, Slide2.JPG, etc.
Copy the Slide...JPG files to a directory on the tablet. This could be using scp, or plugging in a memory card or connecting using USB or accessing a Windows share on the network.
Using Xterm, cd to the directory containing the files and issue the following command:
```
sisusb-slideshow.sh -m 2
```
You may need to use a different value for the -m option. The sisusb-slideshow.sh script takes the same options as the sisbit program.
The script allows you to display each slide in turn (just press return to display the next slide), go backwards, go to the start, etc. Enter Q to exit the script.

X-windows display

Using commercial tools (some free of charge), or using OpenOffice.org, it is possible to export PowerPoint slides as PDF (one file with a page for each slide). This can then be displayed on the tablet using an X-windows-based PDF viewer such as evince (although a custom program which understood the two screens involved would be better).

Advantages

Good quality images

Disadvantages

The PDF display program has to handle a lot of complexity, which is proportional to the complexity of the objects appearing on the slide (as they are each reproduced in the PDF).
As the PDF viewer runs in the CPU and memory limited environment of the tablet it can take significant time (over 10 seconds) to render the next slide, and it is dependent on the complexity of the slide
The PDF viewer may crash or fail to render a slide due to bugs in the program, the PDF or just resource limits

Brief "How To"

Export the PowerPoint presentation to a PDF file using a commercial tool such as Acrobat or PrimoPDF or using OpenOffice.org.
Copy the PDF file to the tablet. This could be using scp, or plugging in a memory card or USB stick or accessing a Windows share on the network.

Using Xterm, issue the following commands:

start-xsisusb
evince --display :1 <PDF-file>

At this point the first slide should be shown. However, to move forwards it is necessary to send keyboard or mouse events to the Xsisusb server using something like VNC. These instructions need to be extended to include information on running VNC server and client locally.