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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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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