A Novel Approach for Vehicle License Plate Location Based on Edge-Color Pair

Abstract

Locating the vehicle license plate plays an important role in the vehicle license plate automatic recognition system. A novel locating approach based on the edge color pair is presented in this paper. Firstly, the edges are detected in a color car image; secondly, a line shape window is made for every edge pixel, and its direction is perpendicular to the direction of the edge and its center is located on the edge pixel, and then the color pattern of the pixels on both sides of the edge point in the window is investigated and the centric edge point of the window is reserved when the color pattern matches the combination of the background color and text color of the plates. Whereafter, a morphological filter is applied to the candidate binary image for removing the regions without the structure feature of the license plate. Finally, the license plate is extracted correctly from the candidate regions by analyzing the texture feature of the plate. The proposed method focuses on matching background color and character color in a license plate and combines its structure feature and texture feature. The experiments on 163 car images that were taken under various conditions show the extraction rate of 98.2%. Integrating color edge detection, edge color pair, mathematical morphology and neural network into our method,the approach offers robustness when dealing with noisy car images, car images in variant lighting conditions and car images with skew number plate.