How to improve image quality in Matlab

Question

I\'m building an \"Optical Character Recognition\" system.

so far the system is capable to identify licence plates in good quality without any noise.

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Answer 1

As you only want to find digits (of which there are only 10), you can use cross-correlation. For this you would Fourier transform the picture of the plate. You also Fourier transform a pattern you want to match a good representation of a picture of the digit 1. Then you multiply in fourier space and inversely Fourier transform the result.

In the final cross-correlation, you will see pronounced peaks, where the pattern overlaps nicely with your image.

You do this 10 times and know where each digit is. Note that you must correct the tilt before you do the cross correlation.

This method has the advantage that you don't have to threshold your image.

There are certainly much more sophisticated algorithms in the literature for assigning number plates. One could for example use Bayes theory to estimate which digit would most likely occur (this helps a lot if you already have a databases of possible numbers).