License plate positioning method based on compressed domain
A license plate positioning and compression domain technology, applied in the field of image processing, can solve the problems of complex license plate positioning calculation, low positioning accuracy and poor real-time performance.
Inactive Publication Date: 2011-02-16
CHONGQING UNIV
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[0004] In view of this, in order to solve the above problems, the present invention discloses a license plate location method based on the compressed domain, which solves the problems of complex calculation, poor real-time performance and low positioning accuracy in the license plate location
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[0072] Preferred embodiments of the present invention will be described in detail below.
[0073] figure 1 It shows that the present invention discloses a process flow of a license plate location method, which includes the following steps:
[0074] 1. Preliminary detection of license plate area
[0075] 1) Huffman encoding (Huffman) decoding is performed on the image compressed data in the detected JPEG format to obtain a run-length encoding (RLE) code stream;
[0076] 2) Perform DCT inverse quantization on the run-length coded code stream to obtain a set of DCT transform coefficient matrices with a size of w×w. Each DCT transform coefficient matrix corresponds to a segmented block with a size of w×w in the detected image. The coefficient The elements of the matrix satisfy: C h，k (i,j);
[0077] Wherein, i=1,...,n; j=1,...,m; n corresponds to the number of blocks vertically segmented when the image in the JPEG format is detected for DCT transformation, and m corresponds to...
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The invention discloses a license plate positioning method which comprises the following steps: constructing a texture vertical frequency matrix and a texture horizontal frequency matrix through partial decompression and extraction of parameters of a DCT transformation coefficient matrix of a compressed domain of a detected image, converting the texture vertical frequency matrix to a license plate binary template matrix through the threshold method, further correcting the license plate binary template matrix through morphological computation, the frequency density value judgment method of thetexture vertical and the horizontal frequency matrixes and the peak and valley threshold method, and further confirming a corresponding license plate region on the detected image. The license plate positioning method can simplify the characteristic quantity of the DCT transformation matrix, improve the operation speed, simplify the complexity of the license plate detection and judgment method by constructing the license plate binary template matrix to judge the license plate region, realize the detection of the multi-license plate region by utilizing the morphological computation and improve the detection precision by introducing the license plate binary template correction mechanism through the frequency density value judgment method of the texture vertical and the horizontal frequency matrixes and the peak and valley threshold method.
Description
technical field [0001] The invention relates to the field of image processing, in particular to a license plate positioning method. Background technique [0002] In the prior art, the research on the license plate location method is mainly divided into the license plate location method based on the color feature and the license plate location method based on the texture feature. The main idea of the license plate location method based on color features is to match the background color and character color of the license plate area in a standard manner. The color difference between the license plate area and the non-license plate area is very large, so the vehicle image is converted from RGB color space to HSI (or HSV) ) color space, and then analyze and extract it, and combine the morphological algorithm and the characteristics of the license plate for positioning. The algorithm based on color features is affected by lighting conditions and climate, such as night, heavy fog...
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IPC IPC(8): G08G1/017G06K9/54G06T7/00
Inventor 张太平尚赵伟袁博唐远炎葛垚胡胜雄
Owner CHONGQING UNIV