Simple script to detect and recognize plate number (Automatic Plate Number Recognition - APNR)

Link to the .pdf report

Steps:

1. Load image

2. Apply blur filter (to remove noise)

3. Convert blurred image to grayscale

4. Apply Sobel filter to find vertical edges (car plates have a high density of vertical lines)

5. Apply threshold with Ostu’s Binarization (Ostu’s binarization will automatically calculate optimal threshold from image histogram)

   

6. Create a rectangular mask of size of 17x3 and apply “closing” filter to detect plate number more clearly

7. Find and fetch contours of possible plates
8. Validate contours and clear out those, that can't be potential plate numbers
   • Is white color dominant?
   • Rotated not more than 15 degrees
   • In Europe, car plate size: 52x11, aspect 4,7272
   • Define min && max area of plate number
9. After (8), apply dilate filter and threshold to validated contours to get numbers and characters

10)Apply Tesseract to extract plate number as a text. Tesseract is an optical character recognition (OCR) engine sponsored by Google.

Final Results