Path: utzoo!utgpu!attcan!uunet!super!udel!rochester!cornell!mailrus!ames!netsys!lamc!well!ewhac
From: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Things to put in IFF picture files
Message-ID: <7401@well.UUCP>
Date: 17 Oct 88 08:32:26 GMT
References: <4937@garfield.MUN.EDU>
Reply-To: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab)
Organization: (-: ACME Flamethrowers.  Mark Ethan Smith, CEO. :-)
Lines: 34
Quote: "Yesterday, I was....  No, that wasn't me."  -- Steve Wright

In article <4937@garfield.MUN.EDU> john13@garfield.MUN.EDU (John Russell) writes:
>I was looking at a display using a custom copperlist, and it occurred to me
>it was a shame the picture could not be displayed that way from any other
>program. So I thought, why not? Why not create an IFF chunk which would
>contain a specialized copperlist? Obviously it would be Amiga-specific, but
>the bitmap data could still be manipulated by any IFF cognizant program on
>any system.
>
	This is probably not a good idea because it violates the IFF rule of
portability.  Copperlists, or a method of describing copperlists, is
inherently non-portable.  Not all machines have hardware registers to report
where the video beam is on-screen, so duplicating the displayable image on
foreign hardware would be difficult to impossible.  Sure you can edit the
bitmap, but since the copperlist is inextricably tied to the layout of the
bitmap, this may not buy you much.

	And before you say it, CAMG *is* portable.  It describes additional
information about what the image looks like, and how it was stored.  HAM
pictures can be decoded on foreign hardware, as well as HALFBRIGHT
pictures.  The HIRES and LACE bits also say something about what the picture
looks like.  So CAMG is portable.

>Also nice would be a way to store fragments of code in a picture file, say to
>deal with a special compression format.  [ ... ]

	Executable code again violates the rule of portability.  You
wouldn't be able to drag the picture over to, say, a 386 with a VGA card,
since you can't execute the embedded code.

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Leo L. Schwab -- The Guy in The Cape	INET: well!ewhac@ucbvax.Berkeley.EDU
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