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Summary of the matched filter algorithm procedure.

The template dictionary

The matched filter template dictionary is a vital component to the success of the program. This dictionary contains a sample of each character, A-Z and 1-9. Each image is obtained from an actual license plate image, converted to black and white, and resized to 256x400 pixels to reduce processing time. Our library of individual character samples was the result of cropping the characters out of several different license plate templates. We finally stored the template dictionary as a cell in MATLAB so we could run the program immediately when we input a license plate image.

Matched filter algorithm

In order to identify characters on the license plate, we must run our test image through a series of steps (Figure 1).

1. image normalization

First, to match the template dictionary samples, every license plate is resized to the standard 256 by 400 pixels. Then, it is processed into a black and white image, with the pixel value 0 corresponding to black and pixel value 1 corresponding to white. This was done to set up for a 2D correlation between the two images.

2. image partition

We then partition the image into 7 different sections, one for each individual character of the license plate. This was done to make the computation more efficient, as we will only compute the correlation between our template dictionary, which contains our library of all of the license plate characters, and the sections of the license plate that contain each individual character.

3. rescale pixel values

Our next step is to shift the pixel values from [0,1] to [-0.5,0.5]. When we compute the correlation between the partitions of the license plate and the template characters, this will ensure we obtain only positive values if the images are the same, and negative values in that region if they are different.

4. two-dimensional correlation

To check for matches between our two images, we perform a correlation between the test license plate and the each entry in the template dictionary. To set this up, our program rescales the pixel values by calculating 1/2 - each pixel value. Now the pixels to range from 1/2 (black) to -1/2 (white). Next we flip the template character upside down and right to left and run the Matlab 'conv2' function. This is equivalent to a 2D correlation between the two images. Two negative numbers (black and black) will return a positive result and two positive numbers (white and white) will return a positive result as well. Through this method, we can obtain all the matches between the two images.

Equation for 2d convolution

convo
Equation for 2D Discrete Convolution.

Matched filter algorithm

LPR
Diagram of Matched Filter Algorithm for License Plate Recognition.

Program results

On each license plate, we section the entire image to obtain each character (110x40). After running a convolution between all the test image sections and the template dictionary, we find the highest correlation values to determine the right character. Our program will return the identified characters in a string, in order of their location on the license plate. This string should match the characters on the actual license plate.

Questions & Answers

are nano particles real
Missy Reply
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Joseph
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Lale Reply
no can't
Lohitha
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Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
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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
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da
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Bhagvanji
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Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
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ya I also want to know the raman spectra
Bhagvanji
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
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Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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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?
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what king of growth are you checking .?
Renato
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, License plate recognition matched filter technique. OpenStax CNX. Dec 18, 2013 Download for free at http://cnx.org/content/col11601/1.1
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