Re: breaking graphics into tables

At 3:27 AM 1/26/99, Dave Leverton wrote:
> Most excellent. But I have to ask something...
> What are the benefits of doing an image this way?

Browsers can handle more than one stream at a time. If you're downloading
an image on a 14.4 modem, then it's not usually receiving 14,400 bits each
second, just because of net traffic. Most browsers can easily handle up to
four streams simultaneously.

There's also the perceptual benefit of having something slap onto the page
immediately, rather than having to wait for the entire graphic to load.
(This is similar to why people frequently make multiple stacked tables,
rather than a single very long table.)

Sliced images are very helpful for navigation bars. In Deborah's UI, each
individual button can be very small. Only the changing area needs to be
sent down the wire.

Sitemap graphics also benefit from slicing... an element which repeats on
many pages, with only a small section changing each page, can have most of
its slices drawn from the cache. This offers an overall speed improvement.


That said, you still don't want more slices than you really need. Each
slice requires a separate HTTP negotiation. A "slice-along-guides" tool
will make more slices than necessary, and will be slower to download that
an image table which uses smarter slicing.

Another thing to look for is per-slice compression methods. In Deborah's
case, the changing center display can likely use a smaller palette than the
overall background of the case. Per-slice compression is particularly
helpful when integrating photographs and large areas of similar color, for
instance.


Fireworks really is the best at all this. You can get a month's worth of
work out of the downloadable demo. It's quite exciting.

jd



John Dowdell, Macromedia Tech Support, San Francisco CA US
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