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In many applications it is necessary to isolate the various objects that populate a scene, starting from their representation, as pixel collections of an image. For example, it could be interesting to isolate an object in foreground from the background . In this case, one talks about segmentation or extraction of regions. The most simple way for isolating different regions is that of doing it on a color basis, or on a gray-intensity basis. Also in this case, the operation can be driven by the histogram that can be helpful in order to establish a gray threshold . All the darker pixels will be mapped to black, while all the lighter ones will be mapped to white. For example, if the histogram presents two evident maxima, it is possible to assign the region of one maximum to the foreground(since it is, for example, lighter) and the region corresponding to the other maximum to the background (since it is, for example, darker). The threshold will be chosen in between the two maxima. Sometimes it is necessary to establish a multiplicity of thresholds, in order to isolate differentregions by means of different gray levels. For color images, the thresholds can be different for different RGB channels.

Apply the Laplacian filter and the LoG filter to the image of Lena.

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Show that the extraction of a background figure by means of a threshold can be implemented by means of nonlinear map g o f g i . What should be the form of this map?

It is a step map, with transition from 0 to 255 set in correspondence of the chosen threshold.

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Employ a program for image processing (ex. Gimp ) in order to isolate (by means of thresholding) the breaks in the image of the broken glass .

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Audio dynamic compression

For audio signals, similarly to what seen for images, one considers the problem of reducing the data necessary to represent a sound, while preserving an acceptable quality of the signal from a perceptual point of view. It is not easy to define, what is meant by "acceptable quality", when one perform a data reduction or, better, a data compression. Ingeneral the qualitative evaluation parameters of the audio compression standards are statistical, based on the results of listening tests made on groups of listeners, representing a wide gamma of users. The audio compression standards are usually founded on the optimization of the dynamics of the signal, that is on the optimization of the number of bits employed for the quantization. A well known example of compression standard isthat of mp3, in which one exploits psychoacoustic phenomena, as the fact that louder sounds mask (make inaudible) softer sounds. In the reproduction of digitalized sounds, the thing that one wants to mask is the quantization noise. In other words, if the sound has a wide dynamics (it is loud) one can adopt a greater quantization step, since the louder quantization noise produced by the rougher subdivision of the quantization levels is anyway masked by the reproduced sound. Still simplifying things in a drastic way, one could say that mp3 varies the step ofquantization according to the dynamics of the sound and in a different way in different bands of frequency. In other words, the signal is divided into many frequency bands (in a similar way as the Equalizer of a Hi-fi system does) and each band is quantized separately. This allowsa reduction of even 20 times of the number of bits with respect to a fixed 16 bit dynamics. Another compression technique is provided by the mu-law (µ-law). This standard is used mainly in audio systems for digital communication in North America and Japan. In this case, the main idea is to modify the dynamicrange of the analogical audio signal before the quantization. Behind these compression techniques, there is once more a psychoacoustic phenomenon that is the fact that our perception of the intensity is not linear but logarithmic-like. In other words, ourperception behaves approximately according to what shown in [link] .

What the mu-law actually performs is a reduction of the dynamic range of the signal by means of an amplitude re-scaling according to the map described in [link] . It is visible how the effect is that of amplifying the small amplitudes, reducing the range of amplitudevalues of the signal (in the sense of big amplitudes) and, as a consequence, increasing the relationship (the amplitude difference) between the sound and thequantization noise. Afterwards, a linear quantization of the non linearly distorted signal is performed. As one wants to play back the digital signal,this is first converted into an analogical signal and then transformed by means of a curve performingan inverse amplitude distortion with respect to that of [link] . The global result is equivalent to a non linear quantization of sound, where the quantization step is bigger (rougher) for bigger amplitudes and smaller (more detailed) for smaller amplitudes. This corresponds, at least from a qualitative point of view,to the way of functioning of our perceptual system. We are more sensitive to the intensity differences in case of soft sounds and lesssensitive in case of loud and very loud sounds. The A-law, adopted in the digital systems in Europe, is very similar to the mu-law.

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Media processing in processing. OpenStax CNX. Nov 10, 2010 Download for free at http://cnx.org/content/col10268/1.14
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