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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.graphics
Subject: Re: rasterops (an alternate view)
Message-ID: <6019@utzoo.UUCP>
Date: Fri, 4-Oct-85 14:46:39 EDT
Article-I.D.: utzoo.6019
Posted: Fri Oct  4 14:46:39 1985
Date-Received: Fri, 4-Oct-85 14:46:39 EDT
References: <588@stc-b.stc.UUCP> <5988@utzoo.UUCP>, <741@terak.UUCP>
Organization: U of Toronto Zoology
Lines: 47

> Raster-ops (aka bit-blt) is a fine paradigm for systems like the
> Macintosh -- medium resolution black-and-white, basically text with
> some intermixed graphics.  But it is inadequate for any system that
> would call itself a true "graphics" system.

If you mean that B+W graphics isn't "true" graphics, come out and say it.
Be prepared to defend this argument, since the vast majority of graphic art
in books, scientific journals, magazines, etc. etc. is line art -- bit/pixel
monochrome, or nearly.  So are most hi-res graphics systems, since it's much
cheaper to do bit/pixel monochrome *well*, and color or gray scale is really
needed only for certain specific applications.

(Henceforth I'll use "color" to mean "color or gray scale", and "B+W" to
mean "bit/pixel monochrome", since the distinctions within those categories
make little difference to the issues here.)

I won't dispute your arguments that RasterOp is of limited use for color,
because of the problems in defining combining functions, although I suspect
there are people out there who would dispute this.  What I will dispute is
that "true graphics" needs color.  Nonsense.  Some kinds of graphics need
color, notably image processing and synthesis.  Other kinds find small
amounts of it very handy, notably VLSI design.  The rest -- much of the
field -- would find it a useful frill, if it was cost-competitive and
quality-competitive with B+W... which it's not.

Your discussion of the sheer amount of data shovelling needed to do a
RasterOp on a multibit image applies to *any* manipulation of such images,
not just to RasterOp.  This supplies an excellent economic argument for
using B+W whenever reasonable and possible, since the volume of data is
much smaller and consequently the speed/hardware_dollar ratio is therefore
much higher.  Printing costs for hardcopy stack up the same way, which is
why B+W line art is so prevalent and color is uncommon by comparison.
Color everywhere would certainly be nice, but for an awful lot of jobs it
simply is not worth the cost.

> I don't think that one should be too surprised that the new-generation
> graphics controller chips, intended for use in high-resolution,
> multiple-pixels-per-plane applications, would not include a full set
> of raster-ops...

Unfortunately, these same chips are being hawked as Great Stuff for hi-res
monochrome as well, which they aren't.  I find no particular indication
that the designers specifically intended them for color and only for color,
especially since they have no monochrome counterparts.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry


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