<< Chapter < Page Chapter >> Page >

image(B);

colormap(gray(256));

axis('image');

The image command works for both type uint8 and double images. The colormap command specifies the range of displayed gray levels, assigning black to 0 and white to 255.It is important to note that if any pixel values are outside the range 0 to 255 (after processing), they will be clipped to 0 or 255 respectivelyin the displayed image. It is also important to note that a floating point pixel value will berounded down ("floored") to an integer before it is displayed. Therefore the maximum number of gray levels that will be displayed onthe monitor is 255, even if the image values take on a continuous range.

Now we will practice some simple operations on the yacht.tif image. Make a horizontally flipped version of the image by reversing theorder of each column. Similarly, create a vertically flipped image. Print your results.

Now, create a "negative" of the image by subtracting each pixel from 255 (here's an example of where conversion to double is necessary.) Print the result.

Finally, multiply each pixel of the original image by 1 . 5 , and print the result.

Inlab report

  1. Hand in two flipped images.
  2. Hand in the negative image.
  3. Hand in the image multiplied by factor of 1.5. What effect did this have?

Pixel distributions

Download the files house.tif and narrow.tif for the following sections.

Histogram of an image

Histogram of an 8-bit image

The histogram of a digital image shows how its pixel intensities are distributed. The pixel intensities vary along the horizontal axis,and the number of pixels at each intensity is plotted vertically, usually as a bar graph.A typical histogram of an 8-bit image is shown in [link] .

Write a simple Matlab function Hist(A) which will plot the histogram of image matrix A . You may use Matlab's hist function, however that function requires a vector as input.An example of using hist to plot a histogram of a matrix would be

x=reshape(A,1,M*N);

hist(x,0:255);

where A is an image, and M and N are the number of rows and columns in A . The reshape command is creating a row vector out of the image matrix, and the hist command plots a histogram with bins centered at [ 0 : 255 ] .

Download the image file house.tif , and read it into Matlab.Test your Hist function on the image. Label the axes of the histogram and give it a title.

Hand in your labeled histogram. Comment on the distribution of the pixel intensities.

Pointwise transformations

Pointwise transformation of image

A pointwise transformation is a function that maps pixels from one intensity to another.An example is shown in [link] . The horizontal axis shows all possible intensitiesof the original image, and the vertical axis shows the intensities of the transformed image. This particular transformation maps the"darker" pixels in the range [ 0 , T 1 ] to a level of zero (black), and similarly maps the "lighter" pixels in [ T 2 , 255 ] to white. Then the pixels in the range [ T 1 , T 2 ] are "stretched out" to use the full scale of [ 0 , 255 ] . This can have the effect of increasing the contrast in an image.

Pointwise transformations will obviously affect the pixel distribution, hence they will change the shape of the histogram.If a pixel transformation can be described by a one-to-one function, y = f ( x ) , then it can be shown that the input and output histograms are approximately related by the following:

Questions & Answers

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
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Purdue digital signal processing labs (ece 438). OpenStax CNX. Sep 14, 2009 Download for free at http://cnx.org/content/col10593/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Purdue digital signal processing labs (ece 438)' conversation and receive update notifications?

Ask