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Wavelet transform-based thresholding method of image

An image binarization and wavelet transform technology, applied in the field of image processing, can solve problems such as difficult text areas and less research on binarization of natural scene images

Inactive Publication Date: 2012-06-13
NANKAI UNIV
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Problems solved by technology

[0003] In recent years, the research on image binarization has continued to deepen, but there are still very few studies on binarization of natural scene images. Only some people have binarized single-character natural scene images.
However, for a complete natural scene image, how to locate the text area itself is a difficult problem

Method used

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  • Wavelet transform-based thresholding method of image
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  • Wavelet transform-based thresholding method of image

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Embodiment Construction

[0036] figure 1 Provided the specific process of the present invention, now in further detail in conjunction with the embodiments of the present invention:

[0037] 1. Convert color image to grayscale image

[0038] Take a color natural scene image I whose width and height are W=388 and H=543 respectively, and first convert it into a grayscale image GRAY according to the following formula. for y ∈ [1, H] has:

[0039] GRAY(x,y)=0.2989*R(I(x,y))+0.5870*G(I(x,y))+0.1140*B(I(x,y))

[0040] Among them, R(.), G(.) and B(.) represent red, green and blue components respectively.

[0041] The converted grayscale image is as follows Figure 4 Shown in (a).

[0042] 2. Background distribution approximation

[0043] First, L-level wavelet decomposition is performed on the grayscale image GRAY to obtain the L-level approximation coefficient LL and the detail coefficients in three directions, which are respectively the horizontal detail coefficient HL, the vertical detail coefficie...

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Abstract

The invention provides a wavelet transform-based thresholding method of an image, and belongs to the field of image processing. In the method, a gray scale of a complete natural scenery image is subjected to wavelet decomposition by utilizing the excellent denoising characteristic of wavelet; foreground characters in the image are removed as noise by virtue of low-pass filter so as to acquire approximate background distribution and foreground distribution; a global threshold is calculated according to the foreground distribution, the global threshold and the background distribution are superposed to form a local threshold which is finally used for image thresholding. The thresholding method provided by the invention can be used for quickly and effectively separating the character part as the foreground to eliminate interference of a complex background, and provides advantages to subsequent character cutting and identifying work. According to the thresholding method provided by the invention, the problem of OCR (optical character recognition) of the natural scenery image can be effectively solved.

Description

technical field [0001] The invention belongs to the technical field of image processing, and in particular relates to an image binarization method based on wavelet transform. Background technique [0002] For images containing text, the purpose of binarization is usually to separate the text part as the foreground. The effect of binarization directly affects the subsequent text segmentation and recognition. Compared with the document image binarization method, the binarization of natural scene images requires the method to be more adaptable and able to handle multiple complex situations at the same time. [0003] In recent years, the research on image binarization has continued to deepen, but there are still very few studies on binarization of natural scene images. Only some people have binarized single-character natural scene images. However, for a complete natural scene image, how to locate the text area itself is a difficult problem. Therefore, it is more general to st...

Claims

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Application Information

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IPC IPC(8): G06K9/38
Inventor 王恺杨巨峰李娇凤焦姣
Owner NANKAI UNIV
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