HDTenEightyP/NetNews huggingface dataset:
From: regie@nelligan.ireq-robot (Regis Houde)
Subject: Synchro problem with TARGA board
Reply-To: regie@nelligan.ireq-robot
Organization: IREQ - Hydro-Quebec
Date: Mon, 11 Jan 1993 21:10:13 GMT

I can't get my TARGA+ board to synchronize properly when it's
connected to a VCR in pause, fasf or rewind mode. Play mode or
live from a camera work just fine. 

Any ideas?

--------------------------------------------------------------------
Regis Houde                             regie@ireq-robot.hydro.qc.ca
Institut de recherche d'Hydro-Quebec    regie@ireq-robot.uucp
1800, montee Sainte-Julie		(514) 652-8107
Varennes, Que., Canada   J3X 1S1	FAX : (514) 652-8435
--------------------------------------------------------------------
From: engp2225@nusunix1.nus.sg (JIN XUECHENG)
Newsgroups: comp.graphics.research
Subject: Fractal.Image
Date: 8 Jan 93 18:17:19 GMT
Organization: National University of Singapore
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I am in research work of fractal representation of images. Could anyone
can provide some images(512x512x256) with known fractal dimensions? It
will be better if source code for generation is provided. Thanks a lot.
E-mail to: engp2225@nusunix1.nus.sg or engp2225@nusvm.bitnet

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From: mikeyang@phoenix.princeton.edu (Michael Kuang-chung Yang)
Newsgroups: comp.graphics.research
Subject: Stereoptic Images?
Date: 7 Jan 93 22:17:14 GMT
Organization: Princeton University
Originator: news@nimaster
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Hello.  Does anyone know of where I can get a pair of stereoptic pictures,
terrain perferably?

Thanks in advance,
Mike


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From: spencer@med.umich.edu (Spencer W. Thomas)
Newsgroups: comp.graphics.research
Subject: Re: Fast dithering techniques?
Date: 11 Jan 93 23:16:54 GMT
Organization: University of Michigan
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In article <11660@sun13.scri.fsu.edu> torbenm@diku.dk (Torben AEgidius Mogensen) writes:
> I once made a variant of F-S that was somewhat faster: instead of
> distributing the error to four neighbouring pixels, distribute it to
> only one.

See Ulichney (MIT Press, 1988) for several variants of this scheme.

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   "Genome Informatician"	|  Univ of Michigan, Ann Arbor, MI 48109
Spencer.W.Thomas@med.umich.edu	|  313-747-2778, FAX 313-764-4133

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From: Tom_Lane@G.GP.CS.CMU.EDU
Newsgroups: comp.graphics.research
Subject: Fast dithering techniques?
Date: 7 Jan 93 19:17:20 GMT
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The free JPEG image compression software currently uses traditional
Floyd-Steinberg dithering when reducing the number of colors in its output.

Even with careful coding, F-S dithering is a remarkably expensive
proposition... in our current release, dithering *alone* (not counting color
selection) takes nearly as much time as JPEG decompression proper.

If anyone is aware of cheaper dithering techniques that give results as good
as F-S, or of implementation tricks to speed up F-S, I'd appreciate hearing
about them.

			thanks, tom lane
			organizer, Independent JPEG Group
			tgl@cs.cmu.edu

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From: craig@cgl.citri.edu.au (Craig McNaughton)
Newsgroups: comp.graphics.research
Subject: re: Fast Dithering Techniques?
Date: 11 Jan 93 23:16:51 GMT
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>Tom_Lane@G.GP.CS.CMU.EDU writes:
>
>>The free JPEG image compression software currently uses traditional
>>Floyd-Steinberg dithering when reducing the number of colors in its output.
>
>>Even with careful coding, F-S dithering is a remarkably expensive
>>proposition... in our current release, dithering *alone* (not counting color
>>selection) takes nearly as much time as JPEG decompression proper.
>
>>If anyone is aware of cheaper dithering techniques that give results as good
>>as F-S, or of implementation tricks to speed up F-S, I'd appreciate hearing
>>about them.
>
>I once made a variant of F-S that was somewhat faster: instead of
>distributing the error to four neighbouring pixels, distribute it to
>only one. The idea is to make the choice of which pixel to distribute
>to random: in the simplest case you randomly choose either the next
>pixel on the same scan-line or the same pixel on the next scan-line.
>You need a fast way to generate random bits, bit a simple
>shift-register method works reasonably well. If you want slightly
>better quality, you randomly choose one of the four pixels that F-S
>would distribute the error to.
>
>The quality is not quite up to the standard of F-S, but nearly so.
>
>	Torben Mogensen (torbenm@diku.dk)

Another alternative is to only propogate error to the next pixel in the path,
but to use a more convoluted path than the standard linear or serpentine scan
that F-S uses.  If you can find a cheap space filling curve to cover your image,
then traversing the image along that curve and propogating error to just the
next pixel produces results that are in many cases better than F-S. (a lot of
the directional artifacts go away).

For more information on this, see :

Cole, "Naive Halftoning", Proceedings of CG International '90, Chua and Kunii eds.
Springer Verlag, 1990  pp 203-222

Witten and Neal "Using Peano Curves for Bilevel display of continuous tone images"
IEEE CG&A, May 1982, pp 47-52

Wyvill and McNaughton, "Three Plus Five Makes Eight, A Simplified Approach to
Halftoning", Scientific Visualisation of Physical Phenomena, Proceedings of CG
International '91, Patrikalakis (ed), Springer Verlag, 1991, pp 379-392.


Craig McNaughton (craig@godzilla.cgl.citri.edu.au)





-- 
Craig McNaughton                  | "If at first you don't succeed, then
craig@godzilla.cgl.citri.edu.au   | just give up and go and watch TV, no
Advanced Computer Graphics Centre | matter whats on."
RMIT, Melbourne, Australia        |	                 Homer J. Simpson

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From: sadasiva@cs.tulane.edu (Thyagarajan Sadasivan)
Newsgroups: comp.graphics.research
Subject: Graphics text
Date: 8 Jan 93 22:17:19 GMT
Organization: Computer Science Dept., Tulane Univ., New Orleans, LA
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I am looking for two good texts on applications of AI and database as related to computer graphics.  Anyone who can help me please send me e-mail at 
	sadasiva@cs.tulane.edu
Thanks.

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From: torbenm@diku.dk (Torben AEgidius Mogensen)
Newsgroups: comp.graphics.research
Subject: Re: Fast dithering techniques?
Date: 9 Jan 93 02:17:21 GMT
Organization: Department of Computer Science, U of Copenhagen
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X-Administrivia-To: graphics-request@scri1.scri.fsu.edu

Tom_Lane@G.GP.CS.CMU.EDU writes:

>The free JPEG image compression software currently uses traditional
>Floyd-Steinberg dithering when reducing the number of colors in its output.

>Even with careful coding, F-S dithering is a remarkably expensive
>proposition... in our current release, dithering *alone* (not counting color
>selection) takes nearly as much time as JPEG decompression proper.

>If anyone is aware of cheaper dithering techniques that give results as good
>as F-S, or of implementation tricks to speed up F-S, I'd appreciate hearing
>about them.

I once made a variant of F-S that was somewhat faster: instead of
distributing the error to four neighbouring pixels, distribute it to
only one. The idea is to make the choice of which pixel to distribute
to random: in the simplest case you randomly choose either the next
pixel on the same scan-line or the same pixel on the next scan-line.
You need a fast way to generate random bits, bit a simple
shift-register method works reasonably well. If you want slightly
better quality, you randomly choose one of the four pixels that F-S
would distribute the error to.

The quality is not quite up to the standard of F-S, but nearly so.

	Torben Mogensen (torbenm@diku.dk)

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From: Tom_Lane@G.GP.CS.CMU.EDU
Newsgroups: comp.graphics.research
Subject: Re: Scaling Down 24-bit Pix
Date: 7 Jan 93 19:17:29 GMT
X-Submissions-To: graphics@scri1.scri.fsu.edu
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tyen@cs.utexas.edu (Anthony Yen) writes:
> I was just talking with a friend of mine today, and he asked about the
> market viability for a package that scales down JPEG format 24-bit or 32-bit
> pictures to 16-bit or 8-bit depths. ... He countered that the package could
> make it in the market if it used the results of some multi-million dollar
> government-sponsored Los Alamos project which focused on how to compress
> high-quality images with little or no data loss.  ...
> Could someone please confirm or refute the possibility of such a piece
> of software?

What your friend is talking about is not data compression in the usual
sense; it is color quantization, and it is HIGHLY lossy.  The name of the
game is to make a visually acceptable approximation to a full-color image
within the constraints of a color-mapped display.  (Incidentally, reduction
for 15- or 16-bit direct-color displays has little to do with reduction for
8-bit color-mapped displays.)

I believe the Los Alamos algorithm referred to is the one used by the
commercial package "Fast Eddie" for Macintosh systems.  Fast Eddie is a
single-purpose program for 24-to-8-bit color quantization.  The blurbs I've
seen for Fast Eddie make great claims for its speed and the quality of the
resulting images, but I have not seen any independent evaluations.

If the underlying research was indeed done at Los Alamos, its results are
probably public domain.  Does anyone know where more information about the
algorithm might be obtained?  I would love to try it out for possible
inclusion in the free JPEG software.

				regards, tom lane
				organizer, Independent JPEG Group

PS: No, I don't think your friend would be well advised to try to build a
commercial color quantizer, but not because there is no demand.  Rather
because (a) there are lots of good free ones, and (b) the demand is within
larger software packages, not as a stand-alone product.  Too bad there is no
functioning marketplace in software components yet...

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From: CDO@ib.rl.ac.uk (C D Osland)
Newsgroups: comp.graphics.research
Subject: Re: Scaling Down 24-bit Pix
Date: 7 Jan 93 19:17:15 GMT
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On 24 Dec 92 17:58:57 GMT <tyen@EDU.UTEXAS.CS> said:
>
>I was just talking with a friend of mine today, and he asked about the
>market viability for a package that scales down JPEG format 24-bit or
>32-bit pictures to 16-bit or 8-bit depths.
>
... loads deleted
>
>Could someone please confirm or refute the possibility of such a piece
>of software?
>
I don't see the point you/he are making.  As far as I know, JPEG
allows the decompression of images to any precision - spatial or colour.
Therefore any JPEG code used back-to-back allows n-bit
originals to be compressed and then decompressed to m-bit finals
without further code being written.

Certainly the point that there are other code systems around (most
image processing systems, including Utah Raster Toolkit) makes the route
via JPEG irrelevant, and the QUANTIZATION (as opposed to PRECISION
CHANGE) that is probably implied by going to 8-bit is as separate
problem, also attacked by the same systems.

Somebody tell me if I'm wrong.

Chris Osland
Atlas Video Facility
Rutherford Appleton Laboratory, UK

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From: amjad@wam.umd.edu (Amjad A. Soomro)
Newsgroups: comp.graphics.research
Subject: Video Test Sequences
Date: 8 Jan 93 10:17:17 GMT
Organization: University of Maryland, College Park
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I am working on video compression algorithms and would like to get 
some standard test sequences to evaluate them. I would very much 
appreciate it if somebody could help me in providing any information
on sources to get these. The common ones which are referred to in 
the literature are:
 
1. ALEXIS
2. MISS AMERICA
3. CINDY
4. DUO
5. QUAD
6. ZOOM/PAN

Any leads in this regard would be very valuable.

Thanks and regards.

Amjad Soomro
Email: amjad@wam.umd.edu




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From: nige@werple.apana.org.au (Nigel Senior)
Newsgroups: comp.graphics.research
Subject: Quantization or Colour Reduction Information required
Summary: Can anybody help me with routines for colour reduction
Keywords: Quantization Colour color
Date: 8 Jan 93 06:17:17 GMT
Organization: werple public-access unix, Melbourne
X-Submissions-To: graphics@scri1.scri.fsu.edu
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: I am doing some work which involves reducing the number of colours in PCX
: images from 256 down to around 25. Currently I am reducing colours by
: merging similar colours, removing colours with small quantities, using
: Heckbert's median cut technique and using Fletcher's box and merge
: technique. While these techniques are good, reducing the number of colours
: in an image to 25 is a bit hit and miss, hence any extra techniques would
: be most appreciated. I am also generally after information related to
: color comparison and transformation specifically related to perceptual
: spaces such as CIE LUV etc. Any suggestions would be most gratefully
: accepted.
: 
: Thank you in advance
: Cheers
: Nigel Senior











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From: ferdinan@oeinck.waterland.wlink.nl (Ferdinand Oeinck)
Newsgroups: comp.graphics.research
Subject: Re: Quantization or Colour Reduction Information required
Keywords: Quantization Colour color
Date: 11 Jan 93 23:16:46 GMT
Organization: My own node in Groningen, NL.
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nige@werple.apana.org.au (Nigel Senior) writes:

> : technique. While these techniques are good, reducing the number of colours
> : in an image to 25 is a bit hit and miss, hence any extra techniques would
> : be most appreciated. I am also generally after information related to
Try the octree algorithm published in 'Graphics Gems 2', page 287,
isbn 0-12-2866165-5.

> : 
> : Thank you in advance
> : Cheers
> : Nigel Senior
Ferdinand.

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From: vardi@xenon.stanford.edu (Moshe Y. Vardi)
Newsgroups: comp.graphics.research
Subject: Applications of Fix-Dimensional Linear Programming
Date: 12 Jan 93 06:16:45 GMT
Organization: Computer Science Department, Stanford University.
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X-Administrivia-To: graphics-request@scri1.scri.fsu.edu

I am interested in finding out about real-life applications
of fixed-dimensional linear programming (as described in
Edelsbruner's "Algorithms in Combinatorial Geometry",
Chapter 10, Section 4, and in Preparata and Shamos' 
"Computational Geometry", Chapter 7, Section 2.5).

Moshe Vardi
vardi@cs.stanford.edu

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Newsgroups: comp.graphics
From: hausner@qucis.queensu.ca (Alejo Hausner)
Subject: fast bitmap rotation
Keywords: shear, rotation, bitmap
Organization: M.Sc, C.S, Queen's, Kingston, Canada.
Date: Sat, 9 Jan 1993 04:53:27 GMT


How to rotate a bitmap using two shears:
(from Foley and van Dam).

Reference: E. Catmull and A.R. Smith, "3-D transformations of
images in scan-line order", SIGGRAPH 80, 279-285.

You want to rotate an n x n array of pixels by an angle phi.
A mathematician would tell you that the necessary transformation
is:

x' = x cos(phi) - y sin(phi)
y' = x sin(phi) + y cos(phi)

But this involves n^2 multiplications, and is slow. 
If we replace it with a two-step transformation, we can do it
faster.  First we go from (x,y) to (u,v), then to (x',y').  The
transformation equations are:

u = x
v = x sin(phi) + y cos(phi)

x' = u sec(phi) - v tan(phi)
y' = v

If you substitute the first pair into the second pair of
equations, you retrieve the original transformation, so it works.


Note that when phi=90 degrees, the secant and tangent terms are
infinite, so the transformation doesn't work.  Hence rotations by
90 and 270 degrees must be handled as special cases.  This isn't
a problem.  Also if phi is close to 90 or 270 degrees, there will
be accuracy problems, and in that case it is better to rotate the
bitmap by 90 (or 270) degrees first, and then rotate by 90-phi
(or 270-phi) degrees.

Algorithm:

sinphi = sin(phi)
cosphi = cos(phi)
secphi = 1.0/cosphi
tanphi = sinphi/cosphi

for x = 1 to n
  xs[x] = x * sinphi
  us[x] = x * secphi
  ys[x] = x * cosphi
  vt[x] = x * tanphi
end for

for x = 1 to n
  u = x
  xsinphi = xs[x]
  for y = 1 to n
    v = xsinphi + yc[y]

    array2[u,v] = array[x,y]
  end for
end for

for v = 1 to n
  yp = v
  vtanphi = vt[v]
  for u = 1 to n
    xp = us[u] - vtanphi

    array[xp,yp] = array2[u,v]
  end for
end for


I hope that works.  I just threw it together on the fly.


Alejo Hausner (hausner@qucis.queensu.ca)

-- 
Alejo Hausner.  (hausner@qucis.queensu.ca)

Newsgroups: comp.graphics
From: flanagan@dms.agames.com (Bob Flanagan)
Subject: DXF file format
Organization: Atari Games Corporation
X-Newsreader: TIN [version 1.1 PL6]
Date: Wed, 6 Jan 1993 16:54:04 GMT

	Does anyone have any references for DXF file format
syntax/structure?

		Bob
-- 

***********************************************************
Bob Flanagan	   	   EMAIL: 	flanagan@agames.com
Atari Games Corporation	   or netcom.com!agames.com!flanagan
Newsgroups: comp.graphics
From: flanagan@dms.agames.com (Bob Flanagan)
Subject: .DXF file format
Organization: Atari Games Corporation
X-Newsreader: TIN [version 1.1 PL6]
Date: Thu, 7 Jan 1993 16:00:31 GMT


	Can anyone give me information on the .DXF graphics file
format?  I need to write I/O routines for this file format so I
need structure and syntax information.  Any references would be
appreciated.

		Bob
-- 

***********************************************************
Bob Flanagan	   	   EMAIL: 	flanagan@agames.com
Atari Games Corporation	   or netcom.com!agames.com!flanagan
From: alien@essex.ac.uk ("Adrian F Clark")
Newsgroups: comp.graphics
Subject: Looking for overprinted (line printer) pictures
Date: 11 Jan 93 14:06:22 GMT
Distribution: comp
Organization: University of Essex, UK

To illustrate a lecture I'm giving, I'd like to have a couple of
largish examples of images presented by overprinted characters on a
line printer.  I have output of Neil Armstrong (or is it Buzz Aldrin?)
and the moon -- but they were printed in about 1978 and have faded
somewhat!  Could anyone give me a pointer to where I can obtain these
(or similar) images by anon FTP?

Many thanks in advance.


--
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 INTERNET: alien%uk.ac.essex@nsfnet-relay.ac.uk          FAX: (+44) 206-872900
 BITNET: alien%uk.ac.essex@ac.uk              PHONE: (+44) 206-872432 (direct)
 Dept ESE, University of Essex, Wivenhoe Park, Colchester, Essex, C04 3SQ, UK.
Newsgroups: comp.graphics
From: joes@tgs.com (Joe Stewart)
Subject: Re: NEED POINT_AND_CLICK UNIX GRAPHICS PACKAGES
Reply-To: joes@tgs.com
Organization: Template Graphics Software (TGS)
Date: Tue, 5 Jan 1993 16:09:13 GMT

In article <4JAN199318001048@ctrvx1.vanderbilt.edu>, umarsa00@ctrvx1.vanderbilt.edu (PROF. A.S. UMAR, (615)322-2459) writes:
|> 
|> I am looking for commercial or shareware point-and-click
|> packages that are able to do contours and surfaces with
|> capabilities to manipulate axis and labels. Fancy postscript
|> labels with symbols is a must.
|> 
|> This is a challenge I never faced before. I am willing to
|> find something but cannot find anything. I do not want a 
|> command line package like IDL or PV-Wave, Mathematica,
|> Speakeasy, gnuplot,....

You may want to take a look at FIGraph, out "two-call" charting and graphing
library built on top of PHIGS.  It comes with both a C and a FORTRAN binding
and it does lines, bars, and pies in addition to contours and surfaces. 

FIGraph does not have a direct point and click (GUI) interface at this time.
However, because it's built on top of FIGARO+, it can be integrated easily
into a GUI.  We are, of course, in the planning stages of a GUI product for
FIGraph.  

One other comment, FIGraph contours both regular and irregular meshes, and 
FIGraph 2.0 will contour arbitrary data by meshing the arbitrary data and 
then contouring the mesh.  In general, what is true for contouring is also
true for surfacing.

If you'd like the usual marketing literature, send a note to info@tgs.com.
If you have specific technical questions, send a note to me, joes@tgs.com.

Joe
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Newsgroups: comp.graphics,comp.graphics.animation,comp.graphics.visualization