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Regions

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

show that the set of all natural number form semi group under the composition of addition
Nikhil Reply
what is the meaning
Dominic
explain and give four Example hyperbolic function
Lukman Reply
_3_2_1
felecia
⅗ ⅔½
felecia
_½+⅔-¾
felecia
The denominator of a certain fraction is 9 more than the numerator. If 6 is added to both terms of the fraction, the value of the fraction becomes 2/3. Find the original fraction. 2. The sum of the least and greatest of 3 consecutive integers is 60. What are the valu
SABAL Reply
1. x + 6 2 -------------- = _ x + 9 + 6 3 x + 6 3 ----------- x -- (cross multiply) x + 15 2 3(x + 6) = 2(x + 15) 3x + 18 = 2x + 30 (-2x from both) x + 18 = 30 (-18 from both) x = 12 Test: 12 + 6 18 2 -------------- = --- = --- 12 + 9 + 6 27 3
Pawel
2. (x) + (x + 2) = 60 2x + 2 = 60 2x = 58 x = 29 29, 30, & 31
Pawel
ok
Ifeanyi
on number 2 question How did you got 2x +2
Ifeanyi
combine like terms. x + x + 2 is same as 2x + 2
Pawel
x*x=2
felecia
2+2x=
felecia
×/×+9+6/1
Debbie
Q2 x+(x+2)+(x+4)=60 3x+6=60 3x+6-6=60-6 3x=54 3x/3=54/3 x=18 :. The numbers are 18,20 and 22
Naagmenkoma
Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 1 more than 3 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 113?
mariel Reply
Mark = x,. Don = 3x + 1 x + 3x + 1 = 113 4x = 112, x = 28 Mark = 28, Don = 85, 28 + 85 = 113
Pawel
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Harshika Reply
what is a solution set?
Harshika
find the subring of gaussian integers?
Rofiqul
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Shirley Reply
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Abdullahi
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Mark
I need quadratic equation link to Alpa Beta
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find the value of 2x=32
Felix Reply
divide by 2 on each side of the equal sign to solve for x
corri
X=16
Michael
Want to review on complex number 1.What are complex number 2.How to solve complex number problems.
Beyan
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Mark
16
Makan
x=16
Makan
use the y -intercept and slope to sketch the graph of the equation y=6x
Only Reply
how do we prove the quadratic formular
Seidu Reply
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Darius
hello, if you have a question about Algebra 2. I may be able to help. I am an Algebra 2 Teacher
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Opoku
what is math number
Tric Reply
4
Trista
x-2y+3z=-3 2x-y+z=7 -x+3y-z=6
Sidiki Reply
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Mark
Solve for the first variable in one of the equations, then substitute the result into the other equation. Point For: (6111,4111,−411)(6111,4111,-411) Equation Form: x=6111,y=4111,z=−411x=6111,y=4111,z=-411
Brenna
(61/11,41/11,−4/11)
Brenna
x=61/11 y=41/11 z=−4/11 x=61/11 y=41/11 z=-4/11
Brenna
Need help solving this problem (2/7)^-2
Simone Reply
x+2y-z=7
Sidiki
what is the coefficient of -4×
Mehri Reply
-1
Shedrak
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Kimberly Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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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