Method of locating license plate of moving vehicle
First Claim
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.
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Abstract
While locating a license plate of a moving vehicle on consecutive images, motion detection is first performed on the consecutive images to detect a moving vehicle image, which is segmented using edge detection, and the segmented moving vehicle image is analyzed to retrieve characteristics for locating a license plate image and determining characters on the located license plate image. As a result, a precise location of the license plate is thus precisely located for further recognition no matter what weathers in which the consecutive images are recorded. The above-mentioned technique requires merely few calculations, is easily implemented, and may be applied on an intelligent digital video recording (DVR) system including many computer-vision functions.
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Citations
15 Claims
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1. A method for locating license plate of a moving vehicle, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification