Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!ucsd!sdcsvax!ucsdhub!hp-sdd!hplabs!hpda!hp-sde!hpfcdc!hpldola!paul
From: paul@hpldola.HP.COM (Paul Bame)
Newsgroups: comp.graphics
Subject: Re: Sun rasterfiles.
Message-ID: <11390007@hpldola.HP.COM>
Date: 2 May 88 19:08:26 GMT
References: <1051@luth.luth.se>
Organization: HP Elec. Design Div. -ColoSpgs
Lines: 22

>
>You can certainly write a RT_BYTE_ENCODED rasterfile pretty easy using the
>appropriate pixrect routine.  You have a pixrect and you dump it to a
>rasterfile with pr_dump().  You can give the RT_BYTE_ENCODED option there.
>

I assume pixrect format is documented in the Sun manuals and I think it's
used on the Mac as well.  It's real simple and goes something like:

	control-byte,data-byte[s],control-byte,data-byte[s]....

	Where the control byte tells how to interpret the following
	data byte(s).  If the sign bit is set (or clear?  can't remember)
	then the number in the lower 7 bits tells how many times to
	repeat the value of the single following data byte.  If the
	sign bit is the other way, the lower 7 bits tell how many data
	bytes follow - which should be copied verbatum to the output
	(this helps prevent 2x expansion on 01010101010 images).

		--Paul Bame
		hplabs!hpldola!paul
		hpldola!paul@hp-labs.csnet
		719-590-5557