Research And Application Of Printing Mottle Evaluation Model Based On Wavelet Analysis

With the continuous development of printing technology,companies are pursuing high-efficiency production and high-quality prints.In actual printing processes,however,a range of printing quality issues can result due to improper handling of the printing equipment,materials,and printing processes.Printing mottle is one of the most common problems in many quality problems,which affects the production of companies and hinders the improvement of printing quality,especially in the field of printing production such as the labels of cigarette and wine.Due to the existence of printing mottle,not only the printing quality is affected,but also to a certain extent the economic benefits of enterprises.Therefore,the quantitative study of printing mottle is an urgent need for enterprises to eliminate mottle and improve printing quality.The traditional method of detection of mottle is mainly visual evaluation of human eyes,but this method is subjectively influenced and has certain limitations.The rapid development of computer digital image processing technology provides a new means for the evaluation of printing mottle,especially wavelet decomposition technology,which can effectively model and evaluate the uniformity of the image.Therefore,based on the wavelet analysis technology and image processing,this paper uses the wavelet detail energy theory,wavelet denoising theory and gray value gradient method to construct a corresponding evaluation model of mottle,and to verify this model is scientific and feasible through the experiment,finally achieved the expected of study,the concrete content is as follows:(1)Using wavelet technique to decompose and reconstruct the image,the detail information in the horizontal,vertical and diagonal direction of the mottled image is used as the evaluation index of the printing mottle,and the matching relation between the evaluation parameters and human eye vision is verified by the response surface analysis method,and the mottle is evaluated by the sum ofthe energy of the detail information in the horizontal,vertical and diagonal direction of the image,then printing mottle evaluation model based on the wavelet detail energy based on the response surface analysis is established.(2)The noise has a certain influence on the printing mottle evaluation,the wavelet denoising is used to denoise the mottled image,and the grayscale gradient of the reconstructed image is used as the evaluation index of the printing mottle,then the printing mottle evaluation model based on wavelet denoising and image grayscale gradient is established.(3)The scientificity and effectiveness of the evaluation model were verified through experiments,the decomposition of the four different wavelet basis functions of Haar,sym5,db5 and bior3.7 is used to evaluate mottle on different types of printed paper.And the results are as followings: a)Based on the response surface analysis of the wavelet detail energy printing mottle evaluation model,the horizontal,vertical,and diagonal direction detail energy of the mottled image is significantly correlated with human visual evaluation.Using details energy summation as the ink spot evaluation index is closely related with the human eye vision.This method is used to deal with four kinds of paper,such as art papers,inkjet paper,newsprint and coated offset,and the results show that the processing results using this evaluation method are superior to the traditional methods.This method has the best effect on the treatment of inkjet paper,the best processing levels are five and seven,and the highest correlation is 0.8199;The treatment effect of coated paper is the worst,the best treatment progression is five and the highest correlation is 0.7120;This method has the equivalent effect on the processing of newsprint and double paper,and the better decomposition progression is five and seven.b)Based on wavelet denoising and gradient of the printing mottle evaluation model,through the classical Robert and Prewitt algorithm,the four wavelet bases were used to process art papers,inkjet paper,newsprint,white cardboard and coated offset respectively.and the results show that the results of this evaluation method are superior to the traditional methods and wavelet detail energy theory methods.Using this method the Haar wavelet function performs the best five-level decomposition of inkjet paper and the correlation is 0.8344,followed by offset paper and white cardboard,and the decomposition progression is better at five and seven levels,next is thenewsprint,and the worst effect was for coated paper.Considering the demand of the evaluation model to the actual production of the enterprise,using the GUI design platform in MATLAB,the paper is integrated with the built printing mottle evaluation model,and the printing mottle evaluation system is developed.The system combines the two kinds of evaluation models,by entering the mottle images,can get the mottle index,instead of the human eye visual detection.This method improves the production efficiency of printing enterprise,has a certain application prospects and market value.