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Process of converting an image of handwritten digits into a standardized format.

Give your digits!: image processing

When an image is acquired, its size and dimensions will vary. Since the database we use is in grayscale and 28x28 pixels large, each input image must be processed so that it also has the same dimensions.

Acquired Image

Convert to grayscale

The acquired image is in RGB format, where each pixel in the image consists of 3 components: the intensity of red, green and blue. Grayscale consists of a single intensity value for each pixel. Therefore, to change each input image to grayscale, we will use the Matlab operator, rgb2gray().

Edge detection

The only information of interest in the input image are the intensities of the actual digits, rather than the intensities of the background. Edge detection will remove background noise and filter the image so that only areas of high contrast (which is the shape of the handwritten digits) remain. The figure below shows the result of applying a simple Sobel edge detector using the edge() command with the threshold set to default.

Result of edge detection with sobel operator.

Dilation: morphological operator

A morphological operator such as dilation processes an image so that its shape is changed in some way. Dilation expands all the boundaries of objects in the image. Dilation in this case also serves to connect any disconnected regions of an outline together. Through the imdilate() command, we can specify how to expand the digit outlines by a structuring element. Depending on the shape of the structuring element, the appearance of the image will change. The ‘ball’ structuring element will be a good choice, since this uses a gradient to make the digits look smoother and rounded out, similar to the way the data is normalized. Depending on how large the digits are written, the size of the structuring element will need adjustment – larger images require a larger structuring element in order to fill more of the outline. In order to get consistent results from dilation, we made sure all writing samples were approximately the same size. The figure below shows the result of dilation.

Dilation of Digit Outlines

Separating individual digits

Now that the only identifiable regions in the image are the digits themselves, the Matlab operator regionprops() with the ‘boundingbox’ option, we will be able to separate the digits into individual images.

Connected regions are identified by ‘boundingbox’

Resize and normalize image

Most input images are much larger than needed and must be rescaled and centered to 28x28 pixels. Imresize() scales the image to 20x20 pixels. Afterwards, zero padding adds zeros to each side of the image, resulting in a 28x28 pixel image. The input image is now standardized and ready to be identified.

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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Elec 301 projects fall 2008. OpenStax CNX. Jan 22, 2009 Download for free at http://cnx.org/content/col10633/1.1
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