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Gray-gradient-based measurement method of mottle of printed product

A technology of image grayscale and measurement method, which is applied in the direction of optical testing for flaws/defects, and can solve problems such as low precision, rough calculation methods, and low efficiency

Inactive Publication Date: 2013-12-18
SHAANXI UNIV OF SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method for measuring ink spots in printed matter based on image gray scale gradients, which solves the problems of low accuracy of existing measurement methods, rough calculation methods, and low efficiency. At the same time, the slight change also reflects the change of the ink mottle information in the overall image grayscale, which comprehensively reflects the ink mottle information in the image, and accurately evaluates the degree of ink mottle in the printed matter

Method used

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  • Gray-gradient-based measurement method of mottle of printed product
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  • Gray-gradient-based measurement method of mottle of printed product

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Embodiment

[0044] Now take the printing ink spots of offset printing paper as an example to specifically illustrate the method and process of measuring ink spots of the present invention.

[0045] (1) Adjust the parameters of the scanner, and place the ink spot sample printed on the offset printing paper to collect the image correctly. The scanner parameters are set as follows: brightness is 50, source is normal, scanning mode is black and white photo, and resolution is 1200DPI.

[0046] (2) Sampling the image printed on offset printing paper, the image size is 42.7mm*42.7mm, the discrete image pixels are 2048*2048, the gray level of the image is 256, and the number of images is 70.

[0047](3) Perform multi-scale discrete wavelet transform on each image, use different wavelet bases to decompose different series, decompose the printed ink spot image into high-frequency image and low-frequency image, remove high-frequency noise, and retain Low-frequency images, and obtain the low-frequen...

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Abstract

The invention discloses a gray-gradient-based measurement method of a mottle of a printed product. The measurement method of the mottle of the printed product comprises the following steps of carrying out image collection on a printed mottle by utilizing a scanner, carrying out analysis and sampling on an image according to the size of a measured region, carrying out multistage wavelet decomposition on the image by utilizing different wavelet bases so as to decompose the image into a high-frequency part and a low-frequency part, retaining main body components of the image, and removing a high-frequency noise part; restoring the mottle image by utilizing discrete wavelet inverse transformation so as to obtain a smooth image of the printed mottle, and counting overall and local changes of the gray gradient of the smooth mottle image, namely the size degree of the mottle. The gray-gradient-based measurement method of the mottle of the printed product is simple and convenient and is high in precision and well solves the problems that the mottle of the printed product is difficult to measure and evaluate.

Description

technical field [0001] The invention belongs to the technical field of quality detection of printed matter, and relates to a method for measuring ink spots of printed matter, in particular to a method for measuring ink spots of printed matter based on image gray scale gradient. Background technique [0002] The so-called printing ink spots, in the actual production of printed matter, are mainly in the solid area or the equal-tone area, the spots and stripes with abnormal colors, inconsistent shades and stripes formed due to uneven distribution of ink. So far, there is no unified and standardized calculation method for the calculation and measurement of ink spots. However, as a common problem in printing quality, printing ink spots have always attracted the attention of printing companies. [0003] At present, the measurement methods of printing ink spots mainly include ISO printing ink spot measurement method, specific parameter ink spot algorithm and artificial visual judg...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/88
Inventor 刘国栋郭凌华冷彩凤梁巧萍
Owner SHAANXI UNIV OF SCI & TECH
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