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Back ground: image processing in matlab

What composes an image?

Each image is composed of an array of M*N pixels (contraction of“picture element”) with M rows and N columns of pixels. Each pixel contains a certain value for red, green and blue. Varying these values for red, green, blue (RGB) we can get almost any color.

Image storage in matlab

Color detection

The RGB format is a practical method to represent color images. Matlab creates three matrices (or three M x N arrays) with each matrix representing normalized components of red, green or blue to read and store each of the frames of the video. Any pixel’s color is determined by the combination of Red, Green and Blue values stored in the three matrices at that pixel’s location. This is how Matlab reads and manipulates .jpg files.

Images:

picture (row, column, rgb value)

For example, picture (12, 78, 1) corresponds to the red component of the pixel at row 12 and column 78; picture(12, 78, 2) corresponds to the green component of the pixel and picture(12, 78, 3) gives us the blue component of the pixel at that location.

Videos:

frames(row, column, rgb value, frame)

Videos have an extra dimension for the frame number. So frames(12,78,1,5) would correspond to the red component of the pixel in the 12th row and 78th column of the 5th frame. To get the entire frame, we could just say frames(:,:,:,5).

Acquiring images from the webcam in matlab

Digitization of the images

How you acquire the images from the camera depends a lot on what software you are using to implement it. Creating the interface between the computer and the drum using a lower level language like C or C++ will give you a lot of flexibility, but it will also involve a lot of work and background knowledge. Fortunately for us, Matlab’s Image Acquisition Toolbox has a variety of simple functions that can be used to create the interface. The next few paragraphs will describe these functions and how we used them in some detail.

For Matlab to recognize the video camera you have to create it as an object using the command obj=videoinput(‘winvideo’) . Matlab will automatically find the webcam connected to your computer. Once it is an object in your workspace you can edit its settings, such as the number of frames per second, to optimize it for your project. preview() and getframe() are two useful functions for determining if the camera has been positioned properly. The first allows you to see what the camera sees, without collecting any data from it, and the second acquires a single snapshot and stores it as in image.

Now we can start recording the video. With the start(obj) command, the camera will be triggered and will start to collect as many frames as specified by the FramesPerTrigger property. These frames are stored in the camera’s buffer memory. These frames are stored in the 4D array as described above.

To retrieve them from the buffer you could use either the getdata() function or the peekdata() function.

Getdata(obj);

When this statement is encountered, the program retrieves all the frames acquired at the last trigger and then empties the buffer.

Peekdata(obj,m);

This function allows us to“peek”at the last M frames collected by the camera. The frames are copied, but not cleared, from the camera’s buffer into Matlab’s workspace.

Both functions take about the same amount of time to run. Interestingly, the number of frames acquired at a time does not affect the execution time much. It takes about as long to acquire 1 frame as it does to acquire 50. Therefore, to make the program more efficient, we should collect large chunks of data at a time.

To make sure that we don’t miss any of the action while the user is waving the drumsticks around in front of the camera, we should also make sure that we can get all the frames from when the program starts running till the user turns of the LEDs. Due to memory limitations, our computer could collect maximum of 240 frames, or about 8 seconds of the video, which is clearly not enough. It is unlikely that your computer could do much better.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Tap that: a virtual drum kit. OpenStax CNX. Dec 19, 2007 Download for free at http://cnx.org/content/col10502/1.1
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