AnyNet AnyNet-12824, Руководство по эксплуатации системы

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Minimum and Optimal resolution character size
The optimal size of a character for an ALPR task is at least 16 pixels in height for characters. A
general rule of OCR is that the smallest unit that defines the recognized object has to be 2x2 pixels. In
terms of ALPR, the smallest unit is the width of the line that compromises the characters on the license
plate. In order to get this line width, the minimum height of the characters has to be 16 pixels.
The characters can, of course, be taller (and will be if higher resolution cameras are used), the 16 pixel
height is just the minimum value. But do note that if the character height is less than 16 pixels, then the
recognition rate will drop drastically. The same is true if the characters are too high. At around 40-50
pixels, the recognition will again drop and sooner or later will reach
0%.
QuickPark® engine i s very robust; therefore, it has the capability of filtering noise from the image. A
dot, if it is too small, can be recognized by the engine as noise in the image. However, if it is
sufficiently big, QuickPark ® will recognize it more effectively without making mistakes.
Low distortion
The camera which acts as the image source for OCR can be installed in many ways. There exist
multiple installation positions that can help in providing optimal images with minimal distortion.
However, there are many cases when the camera cannot be installed in this position causing the object
(license plate) to become distorted on the image. This is why the OCR engine was built to tolerate a 30˚
angle. However, if the pan or tilt angles of the camera exceed 30˚, distortion may significantly reduce
recognition and performance rates.
Fig5: Macro image with enormous
amounts of redundant data. (Bad)
Fig6: A good image with adequate resolution,
not to high, not to low. (Good)