Patent ID: 8290213
Filing Date: 2012-10-16
Classification: G06K

Abstract:
1. A method for locating license plate of a moving vehicle, comprising: transforming a color image, which films a moving vehicle, into a first gray level image; performing edge detection on the first gray level image by using a Sobel operator, so as to generate a second gray level image, wherein the second gray level image comprises a plurality of gradients of the first gray level image; determining a first intermediate gradient, which is from the plurality of gradients of the first gray level image, to be a threshold value, and processing the second gray level image according to the threshold value so as to generate a third gray level image, when a first pixel amount, which is corresponding to the first intermediate gradient and is of the second gray level image, is larger than a second pixel amount, which is corresponding to a second intermediate gradient and is of the second gray level image, by a multiple, wherein the second intermediate gradient is from the plurality of gradients of the first gray level image, and wherein the first intermediate gradient is higher than the second intermediate gradient; performing a morphological operation on the third gray level image, so as to generate a fourth gray level image; scanning the fourth gray level image by using a rectangular mask, so as to determine an edge density of the fourth gray level image; comparing the edge density with a critical edge density, so as to confirm whether there is a license plate image on the fourth gray level image or not; and locating the fourth gray level image so as to locate the license plate image and to display the located license plate image on a screen, when the license plate image is determined to be on the fourth gray level image.