Automatic Number Plate Recognition System
Automatic vehicleidentification is an essential stage in intelligent traffic systems. Nowadays
vehicles play a very big role in transportation. Also the use of vehicles has
been increasing because of population growth and human needs in recent years.
Therefore, control of vehicles is becoming a big problem and much more
difficult to solve. Automatic vehicle identification systems are used for the
purpose of effective control.
Automatic number
plate recognition (ANPR) is a form of automatic vehicle identification. It is
an image processing technology used to identify vehicles by only their number
plates. In this study, the proposed algorithm is based on extraction of plate
region, segmentation of plate characters and recognition of characters.
ANPR can be used to store the images captured by the cameras as well as the
text from the number plate. Systems commonly use infrared lighting to allow the
camera to take the picture at any time of the day. ANPR technology tends to be
region-specific, owing to plate variation from place to place.
Concerns about these systems have centered on
privacy fears of government tracking citizens' movements and media reports of
misidentification and high error rates. However, as they have developed, the
systems have become much more accurate and reliable.
1.1 Project Idea
The increase in the vehicles in day to day life
makes it difficult to monitor each and every vehicle at toll plazas, parking
and societies, so we are developing a system for the personal interest of one
and all that will allow to decrease the human labour and time constraint.
The automatic number plate recognition system
helps us doing it by recognizing the vehicles automatically, tracking the
number plates and storing the numbers in a database.
1.2 Need of the Project
Due to the increase in the number of vehicles a lot of time is spent in
checking and preparing receipts at various places like societies , toll
stations and parking spaces for companies. Thus to reduce the time and the
labor cost, our aim is to implement a system which automatically recognizes the registration
number of vehicles . This system can also be use for security purpose.
1.3
Literature Survey
1.3.1 Image Processing
Image Processing
and Analysis can be defined as the "act of examining images for the
purpose of identifying objects and judging their significance" Image
analyst study the remotely sensed data and attempt through logical process in
detecting, identifying, classifying, measuring and evaluating the significance
of physical and cultural objects.
In computer science, image processing is any form of
signal processing for which the input is an image, such
as photographs or frames of video; the output of image
processing can be either an image or a set of characteristics
or parameters related to the image.
Remote sensing
images are recorded in digital forms and then processed by the computers to produce
images for interpretation purposes. Images are available in two forms -
photographic film form and digital form. Variations in the scene
characteristics are represented as variations in brightness on photographic
films. A particular part of scene reflecting more energy will appear bright
while a different part of the same scene that reflecting less energy will
appear black. Digital image consists of discrete picture elements called
pixels. Associated with each pixel is a number represented as DN (Digital
Number), that depicts the average radiance of relatively small area within a
scene. The size of this area effects the reproduction of details within the
scene. As the pixel size is reduced more scene detail is preserved in digital
representation.
1.3.2 Matrix
Laboratory (MATLAB)
MATLAB,
which stands for MATrix LABoratory, is a state-of-the-art
mathematical software package,
which is used extensively in both academia and industry. It is an interactive
program for numerical computation and data visualization, which along
with its programming capabilities provides a very useful tool for almost all
areas of science and engineering.
It
is a Image Processing Toolbox software that provides a comprehensive set
of reference-standard algorithms and graphical tools for image processing,
analysis, visualization, and algorithm development. You can restore noisy or
degraded images, enhance images for improved intelligibility, extract features,
analyze shapes and textures, and register images. Most toolbox functions are
written in the MATLAB , giving you the ability to inspect the algorithms,
modify the source code, and create your own custom functions.
1.3.4 Algorithm-
The number plate is normalized for brightness and
contrast, and then the characters are segmented to be ready for OCR.
There are six primary algorithms that the software requires for
identifying a license plate:
- Plate
localization and preprocessing – responsible for finding and isolating the
plate on the picture. In this process the captured RGB image is converted
to binary format ,then filtering is
carried out to eliminate the unwanted noise.
- Plate
orientation and sizing – compensates for the skew of the plate and adjusts the
dimensions to the required size. In this process the plate is isolated
from the image and the image of the plate is resized. The centroid of the
first number is located and he plate is cropped accordingly.
- Normalization
– adjusts the brightness and contrast of the image.This process is carried
out to make the numbers more prominent than the background.
- Character
segmentation – finds the individual characters on the plates.In this
process the individual numbers are cropped using region properties
(area,centroid) and bounding box.
- Character
recognition using neural networks.In this process the neural network is
pre trained with a number of fonts to identify the actual cropped number
images.
The complexity of each of
these subsections of the program determines the accuracy of the system. During
the third phase (normalization), this system uses region properties(centroid)
technique to detect black portions in the picture. A median filter may also be used to reduce the visual noise
