Re: Interlaced vs. Non-interlaced GIFs

David Koblas ([email protected])
Sat, 19 Nov 1994 09:43:02 -0800 (PST)


> I'm working on a software package that produces HTML documents and
> GIFs (and other files) from a variety of input formats. Currently,
> all GIFs produced by the package are interlaced, so viewers that have
> the capability (e.g. netscape) can get the incremental display that is
> nice to have over slow connections.
>
> My question is this: is there any downside to always producing
> interlaced images, or should I make it a user preference? For
> example, are there viewers that would choke on interlaced gifs?
> (Mosaic doesn't). Any other issues I should be aware of?

Speaking as one very biased individual, who claims to know something
about GIF images...

Interlaced images are good for two things:
Slow links between client and server
Cool fade in effect

I dislike them for these reasons:
They have a better chance of compressing to a larger file size
They are the _worst_ way you could think of to load images
for an X windows display. You have to scan convert
line at a time and copy to the server, thus adding
another client<->server interaction for every scanline.

The best thing to do is make it an option, since any time I produce
document for a Internal Information System, the server<->client
throughput is 10Mb/s or more and interlaced images are the last
thing that I wan to ship around.

Just my 0.02 cents..

David
[email protected]

ps. On this product of yours, are we going to get the option
of specifing what DPI resolution we would like the images
generated for? Since on of the things that I do a lot of
is when I rasterize line drawings is the following process:
Frame -> postscript @ 150 dpi -> scale 50% -> GIF
This results in an nice anti-aliased image.