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Construction method of document image enhancement

A technology of image enhancement and construction method, which is applied in the field of image processing, can solve the problems of unsatisfactory scanned archive image effects, decreased contrast, inadaptability, etc., and achieve good results, zoom in on local details, and improve the overall contrast.

Inactive Publication Date: 2010-10-13
CHONGQING NORMAL UNIVERSITY
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Problems solved by technology

However, these three methods limit the types of objects to be processed, and have a certain degree of incompatibility for most archival images produced in batches
[0004] The existing noise filtering technology will inevitably produce a certain degree of edge blur after processing, which will further reduce the contrast and bring difficulties to further processing; while the existing contrast enhancement technology, especially the local contrast enhancement technology, mostly enhances The image noise is improved while the contrast is improved, and the effect of processing scanned archive images is not ideal

Method used

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  • Construction method of document image enhancement

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Embodiment Construction

[0028] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0029] as per figure 1 method shown, for figure 2 and 3 The input image (a) in is processed, where the parameters ε, k, λ 1 and lambda 2 The best experimental values ​​of are 4, 5, 1, 10 respectively, which are carried out according to the following steps:

[0030] The first step is to perform a CLAHE operation for each pixel of the input image. If all pixels are processed, output the enhanced image. The calculation formula corresponding to this step is expressed as:

[0031] x' i，j =CLAHE(x i，j ) (1)

[0032] where x i，j , x' i，j represent the pixel being processed and the processed pixel respectively, CLAHE(x i，j ) stands for CLAHE operation.

[0033] In the second step, use the IDAHE method to process the enhanced image output in the first step, and judge whether the pixel being processed is...

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Abstract

The invention discloses a construction method of document image enhancement, which is characterized by comprising the following steps of: 1. combining global contrast enhancement and local contrast enhancement together, i.e. combining a CLAHE (Contrast-Limited Adaptive Histogram Equalization) method and an Lee filter method, and forming a detail-strengthened AHE method; 2. improving a DAHE method, and introducing a gradient amplitude to enable the DAHE method to have image space self-adaptive ability and obtain an IDAHE method; and 3. carrying out experiments by using sampled data to obtain the optimal experimental numerical values of parameters epsilon, k, lambda1 and lambda 2 of input images in different types. The invention has the advantages that the global contrast is improved, the local details are effectively amplified, and imaging is clear.

Description

technical field [0001] The invention relates to the field of image processing, in particular to a construction method for scanning archive images. Background technique [0002] Image enhancement technology mainly includes two methods of spatial domain processing and frequency domain processing. The spatial domain processing method directly processes the pixels in the image, and is basically based on the grayscale mapping transformation. Expressed in a mathematical formula: g(x, y)=T[f(x, y)], T is the selected transformation, and the spatial domain processing method mainly has some operations (reverse transformation, logarithmic transformation, contrast stretching ), algebraic operations (addition, subtraction, multiplication, and division of arithmetic operations, logic operations and or not), histogram equalization (convert the histogram of the original image into a form of uniform distribution), histogram regulation (according to the specified grayscale ratio, perform M...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T5/00
Inventor 杨有
Owner CHONGQING NORMAL UNIVERSITY
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