Presswork ink spot detection method and apparatus

Abstract

The present invention provides a presswork ink spot detection method and apparatus. The method includes the following steps that: the original images of presswork and a reflectivity calibration sample, which are acquired by a scanner, are acquired; the original images of the presswork are sampled, so that a plurality of ink spot images to be detected are obtained; wavelet decomposition, high-frequency de-noising processing and image reconstruction are performed on the plurality of ink spot images, so that smoothed ink spot images can be obtained, and the discrete matrix gray value of the smoothed ink spot images of the presswork is determined; the original images of the presswork are compared with the original images of the reflectivity calibration sample, so that the average reflectivity of the presswork can be determined; and the discrete matrix gray scale value variation coefficient of the smoothed ink spot images of the presswork is determined according to the average reflectivity and the discrete matrix gray value. According to the presswork ink spot detection method and apparatus of the invention, human eye-based sensitivity comparison is used in combination, a digital image processing technology is utilized, and therefore, a detection result can better accord with the subjective perception of human eyes, the relevance of the detection result and human eye visual evaluation can be improved, and simple, high-precision and low-cost presswork ink spot detection can be realized.

Description

technical field [0001] The invention relates to the technical field of quality detection of printed matter, in particular to a method and device for detecting ink spots on printed matter. Background technique [0002] The so-called print mottling can be defined as an unexpected, variable reflection of light in a uniformly toned printed area, in the form of fuzzy clouds, grains, or other regular patterns. In the ISO / IEC13660 standard, a more professional definition is: in all directions of the printed product, the spatial frequency of the density without periodic fluctuation is less than 0.4 period / mm. Printed ink spots are a technical problem that has plagued the papermaking and printing industries for a long time. To study printing spots, use the ink spot index to evaluate ink spots and establish a model, so as to evaluate printed matter ink spots more objectively and solve the problems caused by printed matter ink spots more conveniently. It is of great practical signific...

AI Technical Summary

Problems solved by technology

In recent years, at home and abroad, mainly based on digital image theory and using algorithms for fast data processing to conduct in-depth research on ink stains on printed matter, construct mathematical models, and establish different evaluation systems, but there are still low precision methods, rough algorithms, and human differences. Poor correlation of ocular vision evaluation

[0004] The subjective judgment method is severely limited in practical application because the test is cumbersome, time-consuming and expensive to implement, and is easily affected by factors such as the observer's own knowledge background, emotion, and fatigue.

Most of the existing instrument detection methods use expensive experimental instruments, the cost is high, and it is difficult to popularize

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