Re: ][GIF: What type of file is an RLE file?

[salfter@salfter.diespammersdie.dyndns.org (Scott Alfter)]

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In article <20040416001641.22218.00000518@mb-m06.aol.com>,
Obsbedia2 <obsbedia2@aol.com> wrote:
>Besides gifs, ][GIF has a converter for RLE files.  I tried searching for
>.RLE images on Google, as I do for .GIFS, but only gifs and jpgs came up.
>
>What's an RLE file?

I don't think I've ever run across one, but run-length encoding (RLE) is a
very simple form of data compression, suitable for images of low complexity. 
There must've been a standard of some sort at one time that implemented it
for swapping images...whether it was cross-platform or specific to the Apple
II, I couldn't say.

(RLE typically works by writing a code for an input value, followed by a
count of consecutive occurrences.  Consider this input stream:

00 00 00 00 11 11 22 22 22 33 33 33 33 33

You could encode it this way:

00 04 11 02 22 03 33 05

To decode, you'd read pairs of values and repeat one value the number of
times indicated by the other...repeat 00 four times, 11 twice, etc. to
recover the original stream:

00 00 00 00 11 11 22 22 22 33 33 33 33 33

For some types of data, you might modify the idea to only do this for
certain values (for Hi-Res images, you might only do this for occurrences of
00, 7F, 80, and FF if you have large black areas and white areas in your
images).)

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