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Krishna asks about compression algorithms, lossy versus lossless and
related matters. First let me suggest that you download a paper from my
website. It's on the page at:
http://www.ioa.ucla.edu/~hetrick/vrh001.htm
The title is Designing a WorldWide Web Site: Graphic Formats on the
WorldWide Web
You'll also to download the Adobe Acrobat Reader if you don't already
have it. In this paper, my coauthor and I discuss the issues of images
for people who are (as they say at Scientific American) educated laymen,
but not necessarily computer dudes or dudettes.
It may sound pretty strange, but the issue is really pretty
straightforward. If you want to maintain absolute accuracy of digital
materials, there are relatively few mechanisms for compressing images
very much at all. The storage mechanisms for most of these will be
something pretty huge. None of the "popular" file formats is lossless.
You are likely to need to stick with formats like .tga (Targa), .rle
(Run-Length-Encoded), or .pcx (PhotoPaint).
If you want to maintain "looks", the issue is what are you going to to
with them. If it's to display them on the Web with a fair degree of
accuracy, then the choice of .jpeg (usually .jpg in the PC world to fit
with 8.3 naming conventions) at highest quality is pretty reasonable.
It's even pretty reasonable to use these for images that you might think
would more logically go as .gif files. The really big issue from the
standpoint of a Webmaster is that the files should download fast and
have "high" quality. That can most easily be accomplished with .jpeg
files.
You should be aware that there is a new standard called .png (portable
network graphics) coming and that it combines the best features of .jpeg
with the best features of .gif files. It's not yet clear exactly when
this will be available in browsers. My best guess is that it will be
late this year or early 1999 when the features of HTML 4 are fully
implemented. As soon as we have some functional "popular" software to
do similar measurements as we did with .gif, .jpg, and .pcd files, we
will add them to our list of measures.
HTH.
vh
--
\ / Virginia R. Hetrick, here in sunny California
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