Publication: A simple car plate zooming system
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Date
2012-06-01
Authors
Ong, Lien Pin
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Abstract
Simple digital zooming techniques with linear algorithm introduce artefacts in the zooming results. The presence of artefacts incurs loss of image information and makes the zooming result less appealing for human visualization. One of the implications of low quality zooming in real applications is low recognition rate in a car plate recognition system. The root cause of the artefacts is that simple interpolation techniques presume the continuity of the intensity in an image. In fact, edges of objects with abrupt intensity changes exist in images. It is the reason why artefacts are more distinct at edges region. In order to produce zooming results with lesser artefacts, edge and non-edge regions should be interpolated in different ways due to their different features of intensity continuity. In this thesis, a significant adaptive zooming technique is investigated and identified before it is implemented in a simple car plate zooming system. In the chosen adaptive zooming technique called edge directed interpolation that is based on ramp-edge model, firstly the edges of the input image are located by an edge detection algorithm. After that, the non-edge regions are interpolated by bilinear interpolation while edge regions are interpolated based on the ramp parameters of the edge pixels. The width of the edges in the zooming result is kept similar to the input image so that the zooming result can have good sharpness. This is the uniqueness of the adaptive zooming technique. When the adaptive zooming technique is applied in a simple car plate zooming system, it is proven to be able to produce artefact-free zooming results of car plate images. In addition, the zooming result contains continuous and well-defined edges. The developed car plate zooming system has graphical user interface (GUI) and provides basic functions which include capturing, opening, cropping, zooming and saving of the images.