Classification of vague license plates.
In many cases, we had to enhance the image of a license plate,
but in fact, there is no suitable application or program to achieve this goal and most similar cases on the internet are advertisements and not applicable even after buying.
There is no big key program to enhance images of the target license plates; because based on ambient lighting conditions and the light source direction some parameters setting must be done. These license plates may have different statuses, shapes, colors, sizes, and blurring conditions.
Based on our experience of several years, in this text we classify all the license plates, as very difficult to identify:
Small and far plates.
The small size of the plate is a basic reason it is illegible, which is one of the most difficult cases and anyone can do nothing to enhance, so you must accept the sad truth.
The reflector and the mirror plates
As you are aware, a shiny layer has been drawn up on the plates. in some cases, this transparent layer has the strongest reflections of natural or artificial light sources, and apparently no chance to be readable at all; but, fortunately, in this case, the processes like histogram equalization lead to a good result.
The license plate of quick vehicle
The high speed of the vehicle is the main reason for blurring the plates.
When the sensor of the camera is exposed to the light, (i.e. shuttering time) is one of the main factors of clarity and visibility of the image; if a few values of this parameter add to the high speed of the vehicle, it makes the plate faded, blurred or strained. Some methods can solve these bad motion effects in some cases.
Black plates
With any good lights, night or day, the hole or section of the plate may be dark and unreadable. We’ve named these types of images “Black plates”:
1) Black plate in the shadows
Some of the vehicles run like peak ups due to the plate set under the bumper on the day resulting in shadow becoming the plate black and illegible.
2- Black night plate.
At night, because of very few lights, most of the plates are dark, therefore usually cameras are recorded in IR mode, which, has more noise than usual light and IR videos are grayscale versus vision mode videos which are colorful and RGB.
The license plate at a closed-vision angle
These plates are at a very narrow angle, and this angle can be the result of too above or side vision (right or left). If it is not completely closed, we may be able to apply a geometric transformation on image of plates and get into legible numbers and characters.
plate in the haze or the smoke.
On the cold days of the year, or in crowded and densely inhabited big cities, it would be a short sight distance to see; and this problem would be found on usual days even in small towns because of the morning mist. Using some proposed methods we can clear away the smoke and clean out the fog to read the license plate.
The license plate between the automobile lights
In the night videos/images, the driver had lighted lamps in his automobile, and the glow from these lamps would not even find the position and place of the license plate. This problem would be a lot harder when there were clouds or smoke in the air.