Traffic control by digital imaging cameras - Emerging Trends in Image Processing, Computer Vision, and Pattern Recognition - page 197

6.3 Plate Numbers Recognition
This is done by first determining the plate position, then taking the numbers from the plate
and from a look-up table to compare. The numbers are detected by taking the ones that have
the maximum correlations. The look-up table is a template that contains the numbers from 0
to 9.
The action of recognition includes many functions to obtain the exact result. The image will
be transformed to grayscale. Then the extended-maxima transform is computed. Edge detec-
tion and Strel functions are also used. Finally, plate shaping and filter processing are used to
obtain the final result.
Plate position determination is made by the following steps:
- Transform the image to grayscale.
- Compute the extended-maxima transform.
- Apply edge-detection-type Sobel.
- Determine the line by Strel function.
- Dilate the image.
- Verify the rectangular plate shape.
Plate number recognition (PNR) consists of three parts:
- PNR: in this M-file, the image is being read and then opens a text document where the res-
ult is being displayed at. In this M-file, the plate numbers are being divided each separately
in order to the compare. As shown in Figure 10 .
FIGURE 10 Templates for the plate numbers.
- Creat: in this M-ile, the templates have been made.
- Recognize_numb: in this M-file, it computes the correlation between template and input
image and takes the maximum correlation. Its output is a string containing the leter.
The correlation is made by this part of the code:
(4)
where all numb is from the PNR M-file which is the size templates
(5)
This comutes the correlation between the templates and the input image