HDTenEightyP/NetNews huggingface dataset:
From: neumeist@mdti.com (John W. Neumeister)
Subject: TIFF anf GIF readers
Organization: MDTI San Diego, CA
Distribution: usa
Date: Mon, 28 Sep 1992 20:22:23 GMT

Does anybody know how I can find a routine to read
tiff and gif files on a Silicon Graphics or Sun 
machine?
-- 
smith@mdti.com
From: lake@cwjcc.INS.CWRU.Edu (Dr. Robin Lake)
Newsgroups: comp.graphics,comp.graphics.visualization,comp.edu,sci.edu
Subject: Re: Education in Scientific Visualization
Date: 1 Oct 1992 16:11:30 GMT
Organization: Case Western Reserve Univ. Cleveland, Ohio, (USA)
Reply-To: lake@po.CWRU.Edu
NNTP-Posting-Host: cwjcc.ins.cwru.edu

In article <1992Oct1.142205.11235@colorado.edu> domik@wilkinson.cs.colorado.edu (Gitta Domik) writes:
>I am looking for COURSE OUTLINES (can be short or expanded) that include
>topics in VISUALIZATION. Examples are courses in computer graphics
>or advanced computer graphics, scientific computing or image processing.
>Of course I am specifically interested in courses or seminars that are
>dedicated to visualization. I am trying to classify needs for and approaches to
>visualization courses and will work the results over with participants 
>at a workshop at Visualization '92 in a few weeks from now. We will try to
>create a list of "core topics" for visualization courses. 
>If you prefer fax: 303-492-2844. 
>
>Additionally I am looking for SOFTWARE, PUBLIC DOMAIN DATA, and REFERENCE
>MATERIAL that should be recommended to other educators of visualization
>courses. I will of course give credit to anyone who will help in this
>matter. Results will be published in comp.graphics.visualization. 
>
>
>Thank you.
>Gitta Domik
>Dept. of Computer Science
>University of Colorado
>CB 430
>Boulder, CO. 80309 
>phone: 303-492-4062
>fax: 303-492-2844
>domik@cs.colorado.edu


I recall seeing some visualization course outlines in material sent from
UCLA's Continuing Education Dept.  Sorry, the address is not at hand.

Rob Lake
BP Research
lake@rcwcl1.dnet.bp.com
From: bartb@ogicse.cse.ogi.edu (Bart Butell)
Newsgroups: comp.graphics
Subject: Color Reduction Algorithms
Date: 2 Oct 92 02:31:56 GMT
Article-I.D.: ogicse.43529
Distribution: usa
Organization: Oregon Graduate Institute (formerly OGC), Beaverton, OR


I am looking for an algorithm that will effectively reduce the color
within a 24 bit image into a 16 bit image.  This is called resampling.
Anyone have a source for good algorithms.

BarT
Newsgroups: comp.graphics,alt.graphics
From: steve@monu6.cc.monash.edu.au (Steve Balogh (+61 3 565 4747))
Subject: Re: scanning slides/negatives.
Keywords: slides,negatives,scanner,photostyler
Organization: Monash University, Melbourne, AUSTRALIA
Date: Mon, 5 Oct 1992 03:36:55 GMT

In article <1992Oct02.212558.9303@mmedia.uucp> mcfarlin@mmedia.uucp (David McFarling) writes:
>In <1992Sep23.212509.26254@newstand.syr.edu> cjwong@rodan.acs.syr.edu (Christopher J. Wong) writes:
>
>>Hi, does anyone know if it is possible to get decent images scanning
>>slides/negatives using Aldus Photostyler and a "normal" 
>>scanner(microtek 600Z), not a slide scanner?
>>
>>I've tried tweaking with the gamma curve controls, brightness/contrast
>>, and shawdow/Highlight controls, but have been unable to achieve a 
>>decent image.
>>
>
>Probably not (depends on your definition of "normal").  I'm not
>familiar with Microtek, but "slide" scanners capture light that has
>passed *through* the slide, NOT bounced off it.

Would this work?

=====================================================  Lid of scanner
-----------------------------------------------------  Mirror facing downwards
-----------------------------------------------------  Your slide/negative
=====================================================  Glass surface

I guess that there may be parallax problems and/or color problems due to the
light passing through the image twice. But is it workable?


Regards,
         Steve

----_--_-_-_--_-__-_------_-__---_-___-_----_-____-_-_--__-_--_--___-_-_-_--__-_
Steve Balogh  VK3YMY   (Maths G.14)   | steve@monu6.cc.monash.edu.au
Monash University, Clayton Campus     |      37 54'38.8"S  145 07'47.1"E ...ICBM
Wellington Road, Clayton.  	      |      +61 3 565 4747 Voice (Office)
Melbourne, AUSTRALIA. 3168	      |      +61 3 565 4746 Fax
From: kenyee@sneakers (Ken Yee)
Newsgroups: comp.graphics
Subject: Re: JPEG viewer
Date: 29 Sep 92 14:27:38 EDT

In article <BvBG8K.1KG@watserv1.uwaterloo.ca>  
liboff36@watserv1.uwaterloo.ca (Albert Kemp) writes:
> If you have windows, you may want to try CVIEW386.ZIP.  It's a nice JPEG
> viewer that has some image inhancement tools, and will also allow you to
> view GIF & BMP images as well!  
    WINJP150.zip from oak.oakland.edu in pub/msdos/windows3 has more
    features such as Windows 3.1 support and a slideshow mode.

 ken

p.s., it's also being updated, whereas CVIEW never made it to 1.0 (I  
think).
Newsgroups: comp.graphics,biz.comp.software,comp.groupware
From: IMAGING.CLUB@OFFICE.WANG.COM ("Imaging Club")
Subject: MSG Germany Helps Win Imaging Award
Organization: Mail to News Gateway at Wang Labs
Date: 28 Sep 92 13:22:14 EST


Regarding the recent Wang imaging installations receiving
international awards, the award to BFS in Germany involved
Wang imaging partner MSG Technologies.  They did the part
of the application that reads tapes from a mainframe, merging
over blank forms and storing the result on optical disk.
This application may be very useful for other companies also.
For further information, you can contact Peter Schoerken
at MSG via Wang Office.  For people not on the Wang imaging
network, Email Imaging.Club@OFFICE.Wang.com or send an Email memo
to Peter.Schoerken@OFFICE.Wang.com

Michael.Willett@OFFICE.Wang.com
Newsgroups: comp.graphics
From: pacebes@tid.es (Pedro Acebes Bayon)
Subject: Paralell character-set.
Organization: Telefonica I+D
X-Newsreader: Tin 1.1 PL4
Date: Thu, 1 Oct 1992 13:29:49 GMT

I want to make an application in a 386-computer with a VGA graphics
card where i need to change the ASCII table character-set because i
must use underlined chars and others non standard chars. For example,
i whant that when the user press the 'm' key in the keyboard, a
underlined em will be show in the screen and i don't know how to do
it. The question is : 
	How do to change a character in the ASCII character-set and how
	do to make a new character?

I'm working in text-mode with the Borland C++ 3.0.


Thanks.
-- 

Pedro Antonio Acebes Bayon
E-mail: pacebes@tid.es

Newsgroups: comp.graphics
From: wutcd@chemnitz.guug.de (Joerg Wunsch)
Subject: Dithering algorithm (FAQ?)
Keywords: dithering
Organization: tu-chemnitz
Date: Thu, 1 Oct 1992 15:07:22 GMT

Hi netfolks,

has anyone any pointers where to find something about dithering algo-
rithms? I've read something about `Bayer', `Floyd-Steinberg', `Burkes'
ans `Stucki' within Alchemy Mindworks' Graphics workshop, but i don't
know something on publications about them (possibly on some FTP server?).

	thanx in advance
	J"org

--
J"org Wunsch, TCD GmbH Dresden, R"ahnitzgasse 18, D-O-8060 Dresden
                                                              \     ~.~. 
	joerg_wunsch%bonnie@hadrian.hrz.tu-chemnitz.de         \   ~  | ~ 
	voice: +49-351-5965 137                                 \    ===
From: kpm8447@tesla.njit.edu
Newsgroups: comp.graphics
Subject: <None>
Date: 1 Oct 92 13:15:37 GMT
Organization: New Jersey Institute of Technology

cs.uoregon.edu does not accept anonymous ftp anymore.  Does anyone have
or know where all those shapes can be found?  Also, are there any converter
programs to convert the TDDD or whatever format to .dxf or .3ds (I think
that's the 3-d studio extension)
 - Thanks

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Kirk Membry             ( * * * T H I S   S P A C E   F O R   R E N T * * * )

kpm8447@tesla.njit.edu                                    kpm8447@teak.njit.edu
kmembry@andromeda.rutgers.edu                             kpm8447@maple.njit.edu
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Newsgroups: comp.graphics
From: bpb9204@tamsun.tamu.edu (Brent)
Subject: Macintosh Software seeked
Organization: Texas A&M Univ., Inc.
Date: Sun, 27 Sep 1992 22:30:52 GMT


I'm interested in hearing about freely-distributable (public domain or
shareware) software that is available on the Macintosh to do graphics.
I'm specifically looking for 3D-related graphics programs.

If you are using something or writing software, please let me know
about it.  Also, what hardware requirements (RAM, math coprocessor)
the software has.

I appreciate any and all clues.

-Brent
-- 
------------------------------------------------------------------------------
Brent P. Burton, N5VMG                          Department of Computer Science
bpb9204@tamsun.tamu.edu                                   Texas A&M University
      What are typical family values?      Good buys at WalMart.
From: gary@enigma.asd.sgi.com (Wizard of OZ)
Newsgroups: comp.graphics.explorer
Subject: Re: LatToGeom: Does it use transparency from col
Date: 28 Sep 92 16:33:15 GMT
Reply-To: gary@sgi.com
Organization: Silicon Graphics Computer Systems, Mountain View, CA
NNTP-Posting-Host: enigma.asd.sgi.com

In article <44967@skye.dcs.ed.ac.uk>, gordonc@epcc.ed.ac.uk (Gordon Cameron) writes:
|> From: gordonc@epcc.ed.ac.uk (Gordon Cameron)
|> Newsgroups: comp.graphics.explorer
|> Subject: Re: LatToGeom: Does it use transparency from col
|> Date: Sun, 27 Sep 92 10:32:40 PDT
|> Organization: Edinburgh Parallel Computing Centre
|> Lines: 19
|> 
|> 
|> In article <19vjd4INNfbk@network.ucsd.edu>, haukoos@sdsc.edu (Dana Haukoos) writes:
|> > I've run into the same problem. I've learned from SGI that transparency
|> > is not supported in ver 1.0 of LatToGeom. Ver. 2.0 reportedly will.
|> > 
|> > Dana Haukoos
|> > San Diego Supercomputer Center
|> > haukoos@sdsc.edu
|> 
|> 
|> Does the module LatToGeom2 solve this problem (anyone) ?
|> 

Yes, the module LatToGeom2 fixes this problem. 

To quote from the README file from the SIGGRAPH  Explorer CD...

  There are a few modules that are enhanced versions of existing modules.
  All of these modules are appended with the number 2. The enhancements are :

  IsosurfaceLat2  Added slider for which variable to color vs surface
  IsosurfacePyr2  Added slider for which variable to color vs surface
  LatFunction2            Fixed initialization bug
  LatToGeom2              Added support for transparency

....

|> If so, then its available by anon. ftp etc etc....
|> 	-Gordon.
|> 
|> -- 
|> e|p Gordon Cameron                      |     Phone:+44 31 650 5024(Rm. 2259)
|> c|c Edinburgh Parallel Computing Centre |     Email: gordonc@epcc.ed.ac.uk
|>     oOo The University of Edinburgh oOo |    'So far so good, so now so what'

-- 

Gary Griffin			I just hope I'm still dreamin'
gary@sgi.com			'cause if this is for real
				I'm gonna get very depressed
Think WORLDWIDE		
						Howard T Duck
From: frank@chestnut.chem.upenn.edu (Robert J. Frank)
Newsgroups: comp.graphics.explorer
Subject: 3D plotting and scaling?
Date: 29 Sep 92 12:00:26 GMT
Organization: University of Pennsylvania


Hi..

I just started learning to use Explorer for two days and it's great. But the graphing and plotting is not as well as other softwares. Assume that I have a data file that have X,Y coordinate, How do I use Explorer to plot it? are there any modules that allow you to plot an X,Y,Z data file with the scaling axis?E-mail please. Thank you..

							Rob
Newsgroups: comp.graphics.explorer
From: jcarroll@ferris.cray.com (Jeff Carroll)
Subject: explorer on PCs?
Originator: jcarroll@ferris
Organization: Cray Research, Inc.
Date: 26 Sep 92 16:22:32 CDT



Just a dumb question from somebody who's spread too thin at the moment.

Some time ago I (think I) read about SGI's decision to market a GL
product for PCs. Does that mean that a PC so equipped could run Explorer?

Thanks for email replies.

Jeff Carroll
carroll@reston.cray.com
From: gordonc@epcc.ed.ac.uk (Gordon Cameron)
Newsgroups: comp.graphics.explorer
Subject: Re: LatToGeom: Does it use transparency from col
Date: 27 Sep 92 17:32:40 GMT
Organization: Edinburgh Parallel Computing Centre


In article <19vjd4INNfbk@network.ucsd.edu>, haukoos@sdsc.edu (Dana Haukoos) writes:
> I've run into the same problem. I've learned from SGI that transparency
> is not supported in ver 1.0 of LatToGeom. Ver. 2.0 reportedly will.
> 
> Dana Haukoos
> San Diego Supercomputer Center
> haukoos@sdsc.edu


Does the module LatToGeom2 solve this problem (anyone) ?

If so, then its available by anon. ftp etc etc....
	-Gordon.

-- 
e|p Gordon Cameron                      |     Phone:+44 31 650 5024(Rm. 2259)
c|c Edinburgh Parallel Computing Centre |     Email: gordonc@epcc.ed.ac.uk
    oOo The University of Edinburgh oOo |    'So far so good, so now so what'
From: hashimoto@sgi.com (Roy Hashimoto)
Newsgroups: comp.graphics.explorer
Subject: Re: Arguments to cxGeoScale ??
Date: 6 Oct 1992 18:51:12 GMT
Organization: Silicon Graphics, Inc.
NNTP-Posting-Host: sideout.asd.sgi.com

In article <3857@ra.nrl.navy.mil> ross@orion.nrl.navy.mil (Chris Ross) writes:
>Explorer guys:
>
>The Module Builder's guide defines these transformation routines
>as:
>    cxGeo cxGeoScale(float x, float y, float z)
>    cxGeo cxGeoRotate(float theta, float x, float y, float z)
>
>but in <cx/Geometry.h> they're prototyped as:
>
>void cxGeoRotate(float,float,float,float,float,float,float);
>void cxGeoScale(float,float,float,float,float,float);
>
>Which is right and what are the extra arguments?

The Module Builder's Guide should have been correct.  Unfortunately,
these routines went out with the older interface.  The interface has
been corrected for version 2.0.

For version 1.0 users, the outdated interface is:

void cxGeoRotate(float theta, float x, float y, float z,
	float xc, float yc, float zc);
void cxGeoScale(float x, float y, float z, float xc, float yc, float zc);

The extra arguments were originally supposed to indicate the center of
scaling or rotation.  You should pass them all in as zero.

Roy Hashimoto
hashimoto@sgi.com
Newsgroups: comp.graphics.explorer
From: saeed@a.cs.okstate.edu (SAEED FAISEL)
Subject: what do you know about IDS model ?
Organization: Oklahoma State University, Computer Science, Stillwater
Date: Sun, 4 Oct 92 23:09:26 GMT

I need some info on the IDS model suggested by Cornsweet & Yellot.
And I want to start with a comprehensive bibliography on IDS.

Any email containing any pointers like any work done related to IDS,
specially any publications, etc will be appreciated.

I would also like to correspond with anyone currently working on it.


-- 

Faisel Saeed
Computer Science Department,   Oklahoma State University,   Stillwater, OK 
---------------------------------------------------------------------------
From: ross@orion.nrl.navy.mil (Chris Ross)
Newsgroups: comp.graphics.explorer
Subject: Arguments to cxGeoScale ??
Date: 6 Oct 92 16:51:47 GMT
Article-I.D.: ra.3857
Organization: Naval Research Lab, Washington, DC

Explorer guys:

The Module Builder's guide defines these transformation routines
as:
    cxGeo cxGeoScale(float x, float y, float z)
    cxGeo cxGeoRotate(float theta, float x, float y, float z)

but in <cx/Geometry.h> they're prototyped as:

void cxGeoRotate(float,float,float,float,float,float,float);
void cxGeoScale(float,float,float,float,float,float);

Which is right and what are the extra arguments?

Chris
--
Chris Ross
ross@orion.nrl.navy.mil
Naval Research Lab, Washington, DC
From: rriv@oural.inria.fr (Robert Riviere)
Newsgroups: comp.graphics.explorer
Subject: The SIGGRAPH CDROM
Date: 5 Oct 92 11:01:12 GMT
Organization: Cermics/Inria-Sophia Antipolis France

In article <1a7c4bINN50l@fido.asd.sgi.com> gary@sgi.com writes:
>
>To quote from the README file from the SIGGRAPH  Explorer CD...
>

Here in France nobody knows about this CD...

Someone, some time ago, talked about copying the CD contents on a ftp server, at
epcc or on swedischef.

It would be for us europeans a really nice thing...

Thanks in advance.

-- 
Robert Riviere
(rriv@sophia.inria.fr)				Tel: (33) 93.65.79.06
Inria/CERMICS					Fax: (33) 93.65.77.40
BP 93                              06902	Sophia Antipolis Cedex
Newsgroups: comp.graphics
From: yi@fife.ecn.purdue.edu (Juneho Yi)
Subject: volume formular of a tetrahedron
Organization: Purdue University Engineering Computer Network
Distribution: usa
Date: Mon, 28 Sep 1992 04:30:09 GMT

Hi, netters, 
I have a simple question for you.

I got a formula for computing the volume of a tetrahedron from a Math
table book. Let P1 = (x1, y1, z1), P2 = ...   and P4 =(x4, y4, z4) be 
the four vertices of a tetrahedron.

Then the volume V is,

 V = 1/6 Determinant [(x1, y1, z1, 1), ..., (x4, y4, z4, 1)].
                       first row               fourth row

I know that a tetrahedron is 3-D simplex though I am not a
mathematician.
Could someone tell me where I can find an easy proof of this volume
formular ? What is the negative value mean that the formular can give
? 
I will appreciate direct response to my e-mail address.
Thank you.

-- yi@ecn.purdue.edu
Newsgroups: comp.graphics
From: kr@asacsg.mh.nl (Koos Remigius)
Subject: Re: Trident's Address
Organization: ASAC Nederland b.v.
Date: Wed, 30 Sep 92 08:28:27 GMT

mad@motatl.UUCP (Mark Davidson) writes:
: I am looking for the address or phone number for Trident.  If they have
: a bulletin board number, that would be nice also.
: 
: 
: Thanks,
: Mark
: -- 
: Mark Davidson -  INET: mad@atl.mcd.mot.com  UUCP: {emory,gatech}!motatl!mad
: Motorola Computer Group (MCG)
: 400 Interstate N. Pkwy, Ste 450, Atlanta, GA 30339  Hep Me...Hep Me! I've been
: Phone: 404-933-8628     FAX: 404-952-0892           hypnotized! - Disclaimer


	Mark,

	Trident's BBS is at 415 6911016..

	Enjoy,

		Koos

-- 
Koos Remigius			      kr@mh.nl via internet backbones
Asac Nederland B.V	              uucp: ..!{uunet,hp4nl}!mh.nl!kr
Coenecoop 7, 2741 PG Waddinxveen,  The Netherlands
---------------- "/\/\/\/\/ K O O S /\/\/\/\/\/\/\/" ----------------
Newsgroups: comp.graphics,comp.sys.amiga.hardware,comp.misc
From: conaway@pike.cis.ohio-state.edu (jason william conaway)
Subject: RGB Bandwidth
Followup-To: comp.graphics
Keywords: RGB Bandwidth video
Organization: The Ohio State University Dept. of Computer and Info. Science
Distribution: oh
Date: Wed, 30 Sep 1992 13:46:28 GMT

How does one compute RGB bandwidth in MHz?

To be specific, I need to know the RGB bandwidth of a video signal like this:

resolution:   1280 x 1024 pixels
refresh rate: 120Hz non-interlaced (does interlacing cut the bandwidth in half)
Signal type:  Analog RGB

I'm trying to find a front projection diplay system can handle such demanding
specsifications. I have some catalogs from Electrohome and AmPro. I have yet
to recieve information from Barco. Any sugestions?

Thanks,

Jason W. Conaway
The Artist at Large

 
Newsgroups: comp.graphics
From: bbrown@infonode.ingr.com (Bailey Brown)
Subject: Re: MAC vs. IBM
Organization: Intergraph Corporation, Huntsville, AL.
Date: Thu, 1 Oct 1992 23:08:55 GMT

Peter.Gorny@arbi.informatik.uni-oldenburg.de (Peter Gorny) writes:

>iancu@iil.intel.com (Igal Iancu) writes:
>>Excuse me in advance if this is a FAQ: I have a friend working as a graphics
>>artists, who is used to the Mac environment with FreeHand and PhotoShop.  

>>I am trying to convince her to move to an X86 based machine, mostly because
>>of the prices issue.  Can anybody support me (or her) on this move?  What 
>>are the potential pitfalls when changing the environment?

Photshop is running under Windows now, as is Aldus Photostyler and 
a bunch of other similar applications.  I don't know what FreeHand is,
but I am sure there is a Windows version of it or an equivalent.

PCs are in general harder to use than macs.  However, once you are
in a (Windows) application, there is not much difference.  As long as
some dos-literate person can help out when she needs to do something
drastic, such as installing a 4MB video accelerator, she should be
able to get by.  Windows programs install themselves these days.  You
just keep feeding disks and pressing "OK".

The mac hardware has gotten much more cheaper recently.  However, you
can still get twice as much PC for the same money:

		Mac Performa 600	Gateway 486DX2/66
Price		$2000			$2995	
CPU		32MHz '030		66MHz 486
Memory		4MB			8MB
Disk		120MB			340MB
Video		640x480x8bit		1024x768x16bit &
					800x600x24bit (local bus accel.)
Monitor		not included		15" flat screen (can subst. 17")
Keyboard	not included		included
Mouse		included?		included
Software	Mac SYS7		Win 3.1 and choice of MS application

I think your friend will probably spend much more time inside of 
applications than dinking around with the system.  In this case, having 
2-3X the resources will make her work go much faster and save her more time
overall.

------------
Bailey Brown                               "Above all else, confusion reigns."
Intergraph Corporation                                  
bbrown@casca.b11.ingr.com                              Procol Harum
From: drewsxpa@salem.intel.com (Paul Drews)
Newsgroups: comp.graphics
Subject: Re: COlor scanning on a B&W scanner ??
Date: 5 Oct 92 18:01:04 GMT

In <1992Oct4.061702.18981@muddcs.claremont.edu> ileicht@jarthur.claremont.edu (Spiff) writes:

>I used a black and white video camera with color filters to get
>color digitizations a few years ago. The technique was to take
>the picture with a red, green, and blue filter on then let the
>software map the colors.

>I have a firend with a HP scanjet + and an IBM. Is there any equivalence
>of this for scanners? 

>Thanks..

Yes,  it  can  be  done.   If  you just take your "gray scale thru red
filter",  "gray thru green" and "gray thru blue" images and merge them
as  the red, green, and blue channels of an RGB image, you tend to get
crummy-looking   colors  unless  you  have  excellently-matched  r,g,b
filters.  I have worked around this with "filters" of ordinary colored
plastic found at a stationery store.

I  measured  the fraction of red, green, and blue light transmitted by
each   of  the  red,  green,  and  blue  filters.   This  gives  me  a
"transmission coefficient matrix" M.  If you consider the actual R,G,B
vector  at  a  pixel  to be A, and the resulting measured R,G,B vector
(thru these crummy filters) to be R, you have

  A x M = R

where A and R are 3-vectors, and M is a 3x3 matrix.  You can solve for
A  at every pixel for true-color images or for A at every point in the
color  map  for  color-mapped  images  to  recover the "actual" image.
Consult  your  linear-algrebra  text  for details.  Also note that the
calculations  have to be done in light-intensity space.  You will have
to  convert  the scanner values to light intensities before the matrix
calculations,   and   then   convert   back  to  color-palette  values
afterwards.   Consult  a  graphics  text  for  information about color
theory  and  perception, light intensity, etc.  The linear algebraists
in  the crowd will note that your filters don't have to be red, green,
and blue just so long as they are not linearly dependent.

I  have acquired images with excellent colors using an HP ScanJet Plus
(256  gray  levels)  and  three ordinary chunks of colored plastic.  I
abandoned the approach for two reasons:

  (1) Unless  you  pay  a  LOT  of  money  for very clear, defect-free
      filters,  you get dirt accumulated from all three filters in the
      final image.  It's terrible.

  (2) I got a color scanner.

If  you don't have a scanner already, go out and buy a color one.  The
difference  between the two kinds of scanners is less than the cost of
the  high-quality  filters  you  would  have to buy to do good images.
There's  a  reason  for this.  The difference in technology inside the
scanner  is  just a couple of these filters together with a little bit
of  software that does what I just described.  The only reason to work
with  filters is if you already have a gray-scale scanner.  Watch out,
though:   you  might accidentally learn a whole lot about color theory
and linear algebra :-)

				- PauL Drews
				drewsxpa@ashland.intel.com