Research On Technology Of Green Jade Color Grading Based On HSL Colorimetry

The color of jade is one of the important linkages for evaluation of quality and value of jade.In recent years,many scholars have carried out various kinds of researches on the evaluation of jade color and have made certain achievements in respect of academic aspect.However,it is not difficult to find out that although the experts and scholars have made certain academic achievements on the evaluation of jade color,such achievements have obviously not been applied or promoted in the market.The evaluation of jade color in the market is still disordered,and the reason for such situation lies in that the achievements of academic researches are not suitable for the development of market.Because the academic evaluation of jade color is based on various kinds of instrument indexes,while the complex application of such instrument indexes makes it difficult to be promoted in the market.That is the reason for the embarrassed situation at present,and that is also one of the main objectives for the author to conduct this study.This study applies the method of image acquisition to analyze the HSL value of green jade and confirm its' threshold value,expecting to find out a most simple,convenient and scientific method for the evaluation and grading of color of green jade,looking forward to promote and generalize such research method in jewelry enterprises and in the market,in order to ultimately achieve the objective of providing guidance on the price of jade.In this paper,the green jadeite color is verified by the relevant theoretical researches on colorimetry(This paper mainly focuses on the study of nine kinds of green jadeite colors: bluish green,bright green,yang green,pea green,bean green,melon green,light green,acid green,grayish green(oil-green))which can be marked and expressed by HSL colorimetric parameters;through the theory based practical research,i.e.through a series of analysis and classification for green jadeite color data,a set of accurate and fast color grading method can be established by using the computer.And through continuous testing of the image acquisition results,the color of the green jadeite samples collected in the test can be ensured to be as close to that of the jadeite color as possible,with repeatable image collected and optimized collection conditions.The distribution range and characteristics of the colorimetric parameters of green jadeite are analyzed,and the chromaticity space that characterizes the jadeite green color is selected.Based on the HSL colorimetric characteristics of color distribution,the color types of jadeite green are studied and digitalized,and the color classification of jadeite sample images is implemented through computer programming.According to the variety of the color types of green jadeite samples,the percentage of each pixel and industry rules,the color grade,color index and uniformity of the sample are determined and computer program is prepared.The results of this study:(1)From HSL chromaticity theoretical research of the green jadeite color: The proportion of the green jadeite with the hue value in the range H=100°-119° is not high in the samples,with large span range of the saturation S value at 10%-95%;but the luminance L value is relatively low,with most of them at50% and below.For the green jadeite samples in this hue interval,the yellow tone is relatively obvious,with relatively dark luminance.In very rare cased the hue value is less than 100 °.The proportion of the green jadeite samples with the hue value in the range of H = 120 °-139 ° is high,with both the saturation S value and the luminance L value span quite large.The color types of the green jadeite samples in this hue interval are the most abundant,with relatively pure color,not partial yellow or partial blue.The proportion of the green jadeite samples with the hue value at the range H=140°-159° is medium,with relatively low saturation S value,basically below 60%;large luminance L value span range,at about 10%-80%.The green jadeite samples in this hue interval have an overall blue tone with relatively low saturation.Hue values greater than 160 ° are also rarely seen,some individual obviously bluish jadeite may have the measured hue value up to 170 °.Colorful green jadeite is characterized by high saturation value,generally at 70%-80%,with the highest up to 90%-100%,moderate luminance,at about 20%-30%.The jadeite with luminance value less than5% is too dark and can be divided to the black jadeite series.The one with luminance greater than 80%,or saturation less than 20% is too light in the color,close to white(or colorless),and can be divided into the white jadeite series.With the hue value in the range of 100 °-149 °,the main parameters that influence the glamorous degree of the jadeite green color are the saturation and luminance,which have certain correlation,while the change in the hue has relatively small influence on the glamorous degree of the jadeite green color.(2)The results obtained from the computer programming design based on the HSL colorimetric parameters: The program scans and analyzes the pixels of the green jadeite sample images,and calculates the pixel counts per green color on the sample,i.e.the percentage of the area occupied,and conducts color type classification to obtain the color grade,color index,uniformity and other results.In addition,in the process of editing the program,the rich color levels and uneven color distribution,etc.of the green jadeite color are taken into full consideration,and the program is set to uniform color grading and uneven color grading.The color grading for the uniform green jadeite is mainly conducted by the calculation of the pixel counts,i.e.named after the green pixels with the highest proportion.For example,if yang green ?bluish green,and yang green ? bright green,and yang green ? pea green,and yang green ? bean green,and the yang green ? melon green,and yang green ? light green,and the yang green ? acid green,and yang green ? grayish green(oil-green),and yang green ? white,and bluish green + yang green + bright green + pea green ?80%,the pixel counts of yang green are greater than those of the other pixels,and at the same time,the pixels with rich color account for a large proportion,it can be determined as the yang green grade.More factors need to be considered for the color grading of uneven colored green jadeite.If it is graded according to the general pixel counts,it does not meet the naming convention in the jadeite business.Take the pea green as an example: In the condition that the pea green color has the highest pixel counts according to statistics,distinguish if there is the following situation: bluish green > yang green,and bluish green > bright green,and bluish green + bright green +yang green > 20%.If so,the color grade is determined as: bluish green and the uniformity value are obtained through statistics;otherwise,the following identification is conducted to see if: yang green > bluish green,and yang green >bright green,and bluish green + bright green + yang green >20%.If so,the color grade is determined as: yang green and the uniformity value are obtained through statistics;otherwise,the following identification is conducted to see if: bright green >bluish green,and bright green > yang green,and bluish green + bright green + yang green > 20%.If so,the color grade is determined as: bright green and the uniformity value are obtained through statistics;and in any other cases,it is named as pea green and the uniformity value is obtained through statistics.(3)To verify the reliability of this program,subjective color grading of the samples,Gem Dialogue color card description and HSL colorimetric parameter analysis is conducted.The results obtained are consistent with those of the computer color grading,indicating that the computer color grading system of green jadeite based on HSL colorimetric parameters is stable and fast,with certain feasibility,and can complete the calculation and classification of a variety of green pixels of the green jadeite images very well.It can also make analysis on the uneven jadeite based on the proportion of the various green pixels,and finally determine the grade name,so as to achieve the automatic classification of the green jadeite color through computer programs.This method quantifies and classifies the color of the jadeite from a brand new perspective of HSL colorimetric parameters,and creates a new method for the green jadeite color grading through the technical research of the computer program.In addition,this method can realize fast,objective and repeatable grading of the green jadeite color.