System Documentation with Screen Dumps – the Easy Way.

Overview

Preparing documentation for a computer program will invariably include screen images (screen dumps). If done without preparation the results can be:

• of poor quality
• time consuming to produce and
• result in unnecessarily large files.

Minimum file size is particularly important if the destination is to be the Internet since large files mean long wait times.

The following procedure, while not the only way, is quick, produces high quality images and the smallest file size.

Which file format?

There are many image file formats available and each have their strengths and weaknesses.

• BMP is a bitmap file which produces an exact replica of an image. There is no compression so the files are huge.
• JPG files use lossy compression to produce very small files of continuous tone pictures with millions of colours. JPG is excellent for photographs, but much less satisfactory for screen dumps where vestiges of the lossy compression process blur the sharp edges.
• GIF format uses reversible compression to produce very small files but has a maximum of 256 colours available. It is not so good for continuous tone pictures but is excellent for reproducing a screen dump which has only a limited number of colours.

How to capture the Window

Windows 9x has an in-built screen capture facility. The Print Screen key will copy the screen to the clipboard. Alt-Print Screen will copy the current Window to the clipboard. You could simply paste the clipboard into your document or a Paint program and then save it as a file. But there is an easier way.

Thumbs Plus

Thumbs Plus is designed as the graphical equivalent to XTREE. It displays a directory tree and thumbnail pictures of the graphics files in a selected directory. Thumbs plus is a Shareware program that is readily available from the Internet at http://www.cerious.com

It also has a wonderfully useful feature that is ideal for automating the capturing of screen and window dumps. Auto Clip Save intercepts each PrintScreen or Alt-PrintScreen and instead of sending the image to the clipboard automatically saves them to a sequence of files in the format of your choice.

Edit, Clip Auto Save displays this window

Tick Enable, Select GIF image file format, specify a path in which the captured files are to be stored and a filename prefix and starting sequence number. Each time you PrintScreen or Alt+PrintScreen, a GIF file will be created of the screen image.

Insert the image into your Word processing document or into your Web page

What could be simpler?

Some tips

1. Switch the screen colour depth to 256 colours while using this feature to create GIF files otherwise everytime you will be prompted about reducing the number of colours to create the GIF file. It also takes several seconds to do this.
2. Select a screen resolution to match the output medium. A printed page such as this with 25mm left and right margins is around 600 pixels wide.
3. Don’t scale the image. Changing the size will degrade the image and waste space.

Martin Hood
August 2000