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VISION-LIST Digest 1988 05 13
Vision-List Digest Fri May 13 15:12:39 PDT 1988
- Send submissions to Vision-List@ADS.COM
- Send requests for list membership to Vision-List-Request@ADS.COM
Today's Topics:
Stereo vision
Re: Hexagonal vs. square tesselation
Re: Hexagonal grids
Image & picture file formats - REQUEST FOR INFO!
Psychophysics: BBS Call for Commentators
----------------------------------------------------------------------
Date: Thu, 28 Apr 88 09:29:36 MDT
From: Capt Glen Monaghan <monaghan@usafa.ARPA>
Subject: stereo vision
Hi,
Does anyone have any pointers on "simple" stereo vision? A
couple of my students want to work with two cameras and a digitizer we
have to find the locations of objects. No need to identify what the
objects are, just their location and approximate sizes.
The intention is to augment a sonar device on a robot. The sonar
is swept around, giving range and very crude size information about
the locations of obstacles. There are many probjlems with sonar
reflectivity (or lack thereof) from some materials, orientation of
objects, noisy readings, etc, that would appear to either "go away" or
be reduced or be exchanged for different sorts of problems with an
optical system.
Any ideas? Glen Monaghan, USAF Academy, CO
(719) 472-2475
monaghan@usafa.arpa
------------------------------
Date: 6 May 1988 10:41:46 PDT
From: Shelly Glaser <GLASER%USCVM.BITNET@CUNYVM.CUNY.EDU>
Subject: Re: Hexagonal vs. square tesselation
This is in reply to John Sanger's <JSH@MITRE-BEDFORD.ARPA> note
in Vision-List of May 4.
The advantages of hexagonal vs. cartesian sampling/tessalation are well
known. When the Shannon sampling theorem is applied to two-dimensional
signals (images?) it is very easy to show that the same effective
space-bandwidth-product is achived with fewer sample points if hexagonal
sampling is used (assuming isotropic spatial frequency cut-off in our
pre-sampled signal). This is because a hexagon is a better approximation
of a circle than a square. Another example for the superiority of
hexagonal sampling can be found in cellular machines and related
"image-algebras" where the notion of closest neighbor is not well defined
for cartesian sampling (are there four or eight closest neighbors?) but
is well defined for hexagonal ones. See, for example, remark at page 9
of Rosenfeld's book, "Picture Languages" (Academic Press, 1979).
There was at least one attempt to market a commercial image processing
machine that use hexagonal sampling. This was a "Mathematical
Morphology" (a-la Serra) machine for analysis of biological microscopy
imagery by E. Leitz GMBH (the makers of the Leica cameras) in Germany.
Cartesian sampling won out the battle not because it is better, but
because it is (mostly conceptually) simpler. However, for systems that
use new hardware designed from scratch, I agree that hexagonal sampling
is likely to work better.
Yours
Shelly Glaser
Signal and Image Processing Institute
University of Southern California
MC-0272
Los Angeles, CA 90089-0272
------------------------------
From: mcvax!crin.crin.fr!tombre@uunet.UU.NET
Date: Fri, 6 May 88 13:47:04 +0300
Subject: Hexagonal grids
Hexagonal grids have been in use at least since the Leitz texture analyser
(late 60's or 70's). In fact, if you read THE book on Mathematical
Morphology and Image Analysis by Serra (Academic Press, 1982 1st edition),
you will see that all algorithms are given first for the hexagonal grid,
which has much better topological properties than those of rectangular grids.
Now, some systems are working with hex grid, and others are giving the
possibility to simulate it, i.e. convert to an inner hex representation and
back again for display. This is especially interesting for morphological
operations, whose good topological properties in the continuous space are
better preserved in discrete space with an hexagonal grid.
--- Karl Tombre @ CRIN / INRIA Lorraine
EMAIL : tombre@crin.crin.fr - POST : BP 239, 54506 VANDOEUVRE CEDEX, France
------------------------------
Date: 7 May 88 21:16:13 GMT
From: mcvax!cs.hw.ac.uk!steve@uunet.UU.NET (Steven Salvini)
Subject: Image & picture file formats - REQUEST FOR INFO!
Keywords: Image picture GIF IMG postscript
Organization: Computer Science, Heriot-Watt U., Scotland
Hello vision & graphics experts!
I'm interested in finding out the formats used by vision/graphics
programs for storing their pictures on disk. The machine I'm using
is an IBM PC clone so, for example, an explanation of "GIF" would
be VERY USEFUL and GEM's ".IMG", etc., etc.
Also:
How easy is it to translate from, say GEM's ".IMG" files to "GIF"
- is it possible?
or from these to postscript...
- am I getting too optimistic here?!??!
Please reply by e-mail and I'll summarise to the net.
Steve.
Steven Salvini JANET : steve@uk.ac.hw.cs
Department of Computer Science UUCP : ..!ukc!cs.hw.ac.uk!steve
Heriot-Watt University ARPA : steve@cs.hw.ac.uk
EDINBURGH EH1 3HJ Scotland Phone#: (+44) 31 225 6465 (Ext. 538)
------------------------------
Date: 12 May 88 22:53:45 GMT
From: harnad@princeton.edu
Subject: Psychophysics: BBS Call for Commentators
Keywords: psychophysics, scaling, sensation, philosophy of perception
Organization: Cognitive Science, Princeton University
The following is the abstract of a target article to appear in
Behavioral and Brain Sciences (BBS). All BBS articles are accompanied
by "open peer commentary" from across disciplines and around the
world. For information about serving as a commentator on this article,
send email to harnad@mind.princeton.edu or write to BBS, 20 Nassau
Street, #240, Princeton NJ 08540 [tel: 609-921-7771]. Specialists in
the following areas are encouraged to contribute: psychophysics,
sensory physiology, vision, audition, visual modeling, scaling,
philosophy of perception
Reconciling Fechner and Stevens:
Toward a Unified Psychophysical Theory
Lester E. Krueger
Human Performance Laboratory
Ohio State University
Columbus OH 43210-1285
ts0340@ohstmvsa.ircc.ohio-state.edu or
krueger-l@osu-20.ircc.ohio-state.edu.
How does subjective magnitude, S, increase as physical magnitude or
intensity, I, increases? Direct ratings (magnitude scales; partition
or category scales) can be fitted by the power function, S = aI**b, in
which S equals I raised to a power or exponent, b, and multiplied by a
measure constant, a. The exponent is typically about twice as large
for the magnitude scale (Stevens) as the corresponding partition or
category scale, but the higher exponent may be explained by the over
expansive way people use numbers in making magnitude estimations. The
partition or category scale and the adjusted (for the use of number)
magnitude scale for a given modality or condition generally agree with
the neurelectric scale and the summated just noticeable difference
(jnd) scale. An undue reliance on Weber's law blinded Fechner to the
fact that the true psychophysical scale is approximately a power
function. Fechner and Stevens erred equally about the true
psychophysical power function, whose exponent lies half way between
that of Fechner (i.e., an exponent approaching zero) and that of Stevens.
------------------------------
End of VISION-LIST
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Vision-List Digest Fri May 13 15:12:39 PDT 1988
- Send submissions to Vision-List@ADS.COM
- Send requests for list membership to Vision-List-Request@ADS.COM
Today's Topics:
Stereo vision
Re: Hexagonal vs. square tesselation
Re: Hexagonal grids
Image & picture file formats - REQUEST FOR INFO!
Psychophysics: BBS Call for Commentators
----------------------------------------------------------------------
Date: Thu, 28 Apr 88 09:29:36 MDT
From: Capt Glen Monaghan <monaghan@usafa.ARPA>
Subject: stereo vision
Hi,
Does anyone have any pointers on "simple" stereo vision? A
couple of my students want to work with two cameras and a digitizer we
have to find the locations of objects. No need to identify what the
objects are, just their location and approximate sizes.
The intention is to augment a sonar device on a robot. The sonar
is swept around, giving range and very crude size information about
the locations of obstacles. There are many probjlems with sonar
reflectivity (or lack thereof) from some materials, orientation of
objects, noisy readings, etc, that would appear to either "go away" or
be reduced or be exchanged for different sorts of problems with an
optical system.
Any ideas? Glen Monaghan, USAF Academy, CO
(719) 472-2475
monaghan@usafa.arpa
------------------------------
Date: 6 May 1988 10:41:46 PDT
From: Shelly Glaser <GLASER%USCVM.BITNET@CUNYVM.CUNY.EDU>
Subject: Re: Hexagonal vs. square tesselation
This is in reply to John Sanger's <JSH@MITRE-BEDFORD.ARPA> note
in Vision-List of May 4.
The advantages of hexagonal vs. cartesian sampling/tessalation are well
known. When the Shannon sampling theorem is applied to two-dimensional
signals (images?) it is very easy to show that the same effective
space-bandwidth-product is achived with fewer sample points if hexagonal
sampling is used (assuming isotropic spatial frequency cut-off in our
pre-sampled signal). This is because a hexagon is a better approximation
of a circle than a square. Another example for the superiority of
hexagonal sampling can be found in cellular machines and related
"image-algebras" where the notion of closest neighbor is not well defined
for cartesian sampling (are there four or eight closest neighbors?) but
is well defined for hexagonal ones. See, for example, remark at page 9
of Rosenfeld's book, "Picture Languages" (Academic Press, 1979).
There was at least one attempt to market a commercial image processing
machine that use hexagonal sampling. This was a "Mathematical
Morphology" (a-la Serra) machine for analysis of biological microscopy
imagery by E. Leitz GMBH (the makers of the Leica cameras) in Germany.
Cartesian sampling won out the battle not because it is better, but
because it is (mostly conceptually) simpler. However, for systems that
use new hardware designed from scratch, I agree that hexagonal sampling
is likely to work better.
Yours
Shelly Glaser
Signal and Image Processing Institute
University of Southern California
MC-0272
Los Angeles, CA 90089-0272
------------------------------
From: mcvax!crin.crin.fr!tombre@uunet.UU.NET
Date: Fri, 6 May 88 13:47:04 +0300
Subject: Hexagonal grids
Hexagonal grids have been in use at least since the Leitz texture analyser
(late 60's or 70's). In fact, if you read THE book on Mathematical
Morphology and Image Analysis by Serra (Academic Press, 1982 1st edition),
you will see that all algorithms are given first for the hexagonal grid,
which has much better topological properties than those of rectangular grids.
Now, some systems are working with hex grid, and others are giving the
possibility to simulate it, i.e. convert to an inner hex representation and
back again for display. This is especially interesting for morphological
operations, whose good topological properties in the continuous space are
better preserved in discrete space with an hexagonal grid.
--- Karl Tombre @ CRIN / INRIA Lorraine
EMAIL : tombre@crin.crin.fr - POST : BP 239, 54506 VANDOEUVRE CEDEX, France
------------------------------
Date: 7 May 88 21:16:13 GMT
From: mcvax!cs.hw.ac.uk!steve@uunet.UU.NET (Steven Salvini)
Subject: Image & picture file formats - REQUEST FOR INFO!
Keywords: Image picture GIF IMG postscript
Organization: Computer Science, Heriot-Watt U., Scotland
Hello vision & graphics experts!
I'm interested in finding out the formats used by vision/graphics
programs for storing their pictures on disk. The machine I'm using
is an IBM PC clone so, for example, an explanation of "GIF" would
be VERY USEFUL and GEM's ".IMG", etc., etc.
Also:
How easy is it to translate from, say GEM's ".IMG" files to "GIF"
- is it possible?
or from these to postscript...
- am I getting too optimistic here?!??!
Please reply by e-mail and I'll summarise to the net.
Steve.
Steven Salvini JANET : steve@uk.ac.hw.cs
Department of Computer Science UUCP : ..!ukc!cs.hw.ac.uk!steve
Heriot-Watt University ARPA : steve@cs.hw.ac.uk
EDINBURGH EH1 3HJ Scotland Phone#: (+44) 31 225 6465 (Ext. 538)
------------------------------
Date: 12 May 88 22:53:45 GMT
From: harnad@princeton.edu
Subject: Psychophysics: BBS Call for Commentators
Keywords: psychophysics, scaling, sensation, philosophy of perception
Organization: Cognitive Science, Princeton University
The following is the abstract of a target article to appear in
Behavioral and Brain Sciences (BBS). All BBS articles are accompanied
by "open peer commentary" from across disciplines and around the
world. For information about serving as a commentator on this article,
send email to harnad@mind.princeton.edu or write to BBS, 20 Nassau
Street, #240, Princeton NJ 08540 [tel: 609-921-7771]. Specialists in
the following areas are encouraged to contribute: psychophysics,
sensory physiology, vision, audition, visual modeling, scaling,
philosophy of perception
Reconciling Fechner and Stevens:
Toward a Unified Psychophysical Theory
Lester E. Krueger
Human Performance Laboratory
Ohio State University
Columbus OH 43210-1285
ts0340@ohstmvsa.ircc.ohio-state.edu or
krueger-l@osu-20.ircc.ohio-state.edu.
How does subjective magnitude, S, increase as physical magnitude or
intensity, I, increases? Direct ratings (magnitude scales; partition
or category scales) can be fitted by the power function, S = aI**b, in
which S equals I raised to a power or exponent, b, and multiplied by a
measure constant, a. The exponent is typically about twice as large
for the magnitude scale (Stevens) as the corresponding partition or
category scale, but the higher exponent may be explained by the over
expansive way people use numbers in making magnitude estimations. The
partition or category scale and the adjusted (for the use of number)
magnitude scale for a given modality or condition generally agree with
the neurelectric scale and the summated just noticeable difference
(jnd) scale. An undue reliance on Weber's law blinded Fechner to the
fact that the true psychophysical scale is approximately a power
function. Fechner and Stevens erred equally about the true
psychophysical power function, whose exponent lies half way between
that of Fechner (i.e., an exponent approaching zero) and that of Stevens.
------------------------------
End of VISION-LIST
********************
