4.6 Technology Factors
• A format proposed by Adobe. This is not a ‘standard’, but is very widely accepted.
• When documents are presented in pdf format their original layout is preserved (HTML will actually change the look/layout of a document), but the files become hard/impossible to work with.
• A special plug-in is required to view these files.
• We can make a file smaller by compressing it (unless it is already compressed, then it gets larger)
• File compression can make files harder to use in Web documents, but the smaller size makes them faster to download. A good rule of thumb is that when the file is MB is size, compression will have a large impact.
• Many file formats have compression built in, including,
images - JPG, GIF
video - MPEG, AVI
programs - installation programs are normally compressed
• Typical compression formats include,
zip - zip, medium range compression
gz - g-zip - good compression
Z - unix compression
Stuffit - A Mac compression format
• Some files, such as text, will become 1/10 of their original size.
• Two good formats are,
GIF - well suited to limited color images - no loss in compression. Use these for line images, technical drawings, etc
JPG - well suited to photographs - image can be highly compressed with minimal distortion. Use these for photographs.
• Digital cameras will permit image capture and storage - images in JPG format are best.
• Scanners will capture images, but this is a poor alternative as the image sizes are larger and image quality is poorer
- Photographs tend to become grainy when scanned.
- Line drawings become blurred.
• Screen captures are also possible, but do these with a lower color resolution on the screen (256 color mode).
• These are not video, but moving drawings/cartoons.
• Animations are limited, but are best done with animated gif files.
• Other options include,
- java programs
- special plug-ins such as shockwave
• Streaming built into Netscape for real-time video.
• We can also get special plug-ins that will allow us to see video files,
- MPEG very popular, good compression, and fault tolerant.
- AVI popular on PC platforms, but limited drivers elsewhere.
- Apple Quicktime.
• Real-time video conferencing is possible, but not yet practical.
• Sound files are poorly supported, and most require special plugins,
- real audio
- wav audio
4.6.7 Other Program Files
• We can connect any type of non-standard computer file to our pages, such as a Microsoft Excel file ‘.xls’.
• To do this we need to,
1. Put the file in our web directory
2. Link it to one or more HTML pages
3. Have the system administrator add this as a MIME type to the system.
4. When you click on the link to the file in Netscape it will ask you to choose an application. For an excel file you would want to choose ‘\program files\office97\excel’. This will automatically start when you choose the file next time. If you did not do step 3, or did not choose an application you would be asked to save the file.
• This is an excellent way to extend the capabilities of a web browser.