Automatic Number Plate Recognition System

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:

1. 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.
2. 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.
3. Normalization – adjusts the brightness and contrast of the image.This process is carried out to make the numbers more prominent than the background.
4. 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.
5. 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