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probability that the engine will recognize the license plate. It is also worth noting that blurring can be
caused by many other factors and not just a small image size.
What is the optimum character size and resolution?
The optimal size of the characters on the given image is essential. In terms of character size, there is one
typical misconception. Many think that the higher the resolution, the better. This statement,
however, is not true. Neither images with too high or too low resolution will work properly.
High resolution
High-resolution (macro) images contain a lot of redundant data. Characters can be easily defined
based on the edges of a character. No other information is needed. So much so, that the pixels within
a character are irrelevant in terms of shape/pattern recognition. These are just pixels that waste the
resources of computation. Therefore, the resolution is optimized for a certain character size.
Although this size can be adjusted, it has to be noted that adjusting the default character size can
cause problems if characters are too tall.
Low Resolution
Images containing less information than what the engine needs should be considered as low-
resolution images. Of course, it has to be noted that even if the characters are smaller in resolution
than the required minimum, the engine may deliver correct results, but it will not consistently
recognize these images. If one would feed the engine a few thousand low-resolution images, the
recognition rate would drop over time.
Fig3: An adequately sharp image. (Good)
Fig4: A blurry image with a hard to read license
plate. (Bad)
