数字影像输出设备色彩性能分析

为了充分认识数字影像输出设备的色彩表现能力,对色域的确定和分析方法进行了探讨.采用的方法是,在CIELAB色空间中确定色域边界,并求解色域体积、分体积,以及白点、黑点和6个主色调最大彩度色的色度值,同时给出CIELAB L*a*b*三维和CIEXYZ_xy、CIELAB_a*b*二维色域边界图.在3种类型5个设备上进行了应用,得到的指标特性符合其实用特性.实验结果表明,色域体积和分体积能够反映设备输出颜色范围的总体大小和不同色调区域的大小,白点、黑点和主要色调的色度值可反映白色、黑色和饱和色的表现力度,三维、二维色域边界图则直观地显示了不同设备色域的差异.     

纺织品颜色分类算法比较研究

探讨和比较纺织品颜色分类算法。优选了均匀且色域宽阔的L*a*b*颜色空间;基于机器视觉和图像处理技术,通过仿真试验比较分析了支持向量机、最小二乘支持向量机和自组织映射神经网络三种算法的训练和测试样本的准确率和运行时间。试验结果表明:对于小样本集,最小二乘支持向量机算法的分类准确率及收敛速度要优于支持向量机算法和自组织映射神经网络算法。认为:最小二乘支持向量机分类算法在纺织品颜色在线分类方面具有更好的应用潜力。     

基于计算机视觉的午餐肉颜色测定系统研究

目的建立一种对午餐肉样品物理特性要求较少,能对物料表面整体颜色进行准确测量的无损检测方法。方法采用计算机视觉系统对24色色彩测试板测定得L,a,b值,使用色彩色差计对24色色彩测试板测得L~*,a~*,b~*值,对两组数据进行线性回归;计算机视觉系统测定午餐肉的L,a,b值,带入回归方程得到标准的L,a,b值,色彩色差计对午餐肉测定得L~*,a~*,b~*值,用SPSS软件对得到的标准L,a,b值和L~*,a~*,b~*值进行成对样本检验。结果 L,a,b值回归方程的相关系数r~2分别为0.9900、0.9707和0.9801,有高度相关性;午餐肉标准L,a,b值和L~*,a~*,b~*值成对样本检验得到的P值分别为0.146、0.087、0.109,大于显著性水平0.05,回归方程转换值与色差计测定结果无显著差异。结论本文建立的基于计算机视觉的午餐肉颜色测定方法可以准确测定午餐肉颜色,其效果可以代替色差计。     

喷墨印花中的计算机图像处理(二)

<正>二、色彩空间与色域1,基本概念在RGB、CMYK和L*a*b*色彩空间内,编辑图像的本质区别是工作的色域不同。色域是指某种表色模式能表达的颜色数量所构成的颜色区域,也指具体介质,如屏幕显示、打印机输出及印刷复制所能表现的颜色范围。自然界中可见光谱的颜色组成了最大的色域空间,该色域空间包含了人眼能看到的所有颜色。在各种色彩模式中,L*a*b*色域空间最大,它包含了RGB、CMYK模式中的所有颜色。人们在工作中所使     

基于旋转球算法的图像色域的可视化

根据源色域是否基于图像可以将色域映射分成两类,设备到设备和图像到设备。图像到设备的方法考虑到了图像色域是设备色域的一个有限子集,这样就能够避免图像的色域被过度压缩从而可以更好地保护颜色的色貌。在一个基于图像的色域映射算法中图像色域的几何精确度是很重要的因素。本文针对图像色域的构建,提出了一种精确度较高的基于旋转球算法(Ball-Pivoting Algorithm)的图像色域的三维可视化的方法。首先我们用一个通常的分析转换方法将要输出的图像从RGB空间转换到CIEL*a*b*颜色空间,然后我们将CIEL*a*b*颜色空间离散化,再将图像的像素点量化到离散空间的网格点。最后基于旋转球算法实现图像色域的网格点重构。实验结果表明提出的方法能够在不失精确度的同时保持较快的速度,这对于开发基于图像的实时色域映射算法有重要意义。     

基于光谱分析的织物色差检测

为有效检测出织物色差,将主成分分析(PCA)与极限学习机(ELM)相结合的方法应用于织物色差检测。首先,利用光纤光谱仪采集净色织物的光谱反射率数据及其对应的颜色特征值L*、a*、b*,建立PCA-ELM预测模型,获取光谱反射率相关数据与L*、a*、b*值之间的映射关系,避免冗长的公式计算。然后,利用CMC(2∶1)色差公式计算标准样本和测试样本之间的色差,并与光纤光谱仪测量值进行对比。实验结果表明,利用PCA-ELM模型获取的L*、a*、b*值与光谱仪测量值各分量的平均误差为0.116 1、0.174 3、0.204 8。在色差检测实验中,利用CMC(2∶1)色差公式得到的织物色差与光谱仪测量值最大误差为0.66 NBS,平均误差为0.087 5 NBS。     

焦糖色对老抽酱油色度的影响

对添加焦糖色配制的老抽酱油的色度(L、a、b及△E值)变化进行了研究.研究结果表明:焦糖色品种、浓度均对老抽酱油的色度产生显著影响.配制后加热温度达85℃以上后,对老抽产品的L、a和b值影响不显著,加热时间对老抽产品L、a和b值影响不显著,但添加焦糖色后老抽酱油L、a和b值在贮存期间稳定性不佳.本试验得到添加焦糖色的L、a和b值理论拟合曲线,可作为配制老抽酱油的指导.     

CIELAB色空间原理在血红蛋白色素呈色效果评价中的应用

目的:使用色差计测量并评价应用猪血亚硝基血红蛋白色素的肉制品颜色,以代替肉眼作出客观定量的判定。方法:对使用本实验室工作人员制备色素的肉制品,用色差计测量不同保存时间的样品表面和内部的CIE1976(L*a*b*)色空间的CIELAB值,并计算色差。结果:肉制品的表面颜色会随着保存时间的增加而变差,反映在a*值由8降到6左右,b*值由13升到15左右;而肉制品的内部颜色则保持粉红色,a*值基本保持不变,而b*值降到10左右;同时,用冷冻干燥保存的色素制作的肉制品颜色优于其它保存方法,反映在较高的a*值、b*值和较低的L*值。结论:使用色差计测定CIE1976色空间及色差值,可反映肉制品颜色的差异及变化趋势;与感官判断的结论一致,并获得定量的结果。     

棕色和黄色包装纸的染色

牛皮包装纸和纸板染色的合适染料品种为直接染料或碱性染料,合适染料组合为棕色+黄色+蓝色或黑色,或红色+黄色+蓝色或黑色。牛皮箱板纸调色程序可根据纸张的本色与目标值的差异确定所需的染料品种,选用一种棕色染料和一种黄色染料配合调色,做一系列不同染料用量下的抄片,检测其色相变化,在CIE-L*,a*,b*色相图中画出纸张用该种染料染色后的色相变化趋势曲线。根据染料的色相变化趋势曲线,通过作图配色法调整染料配比和用量,直到达到目标a*,b*值。最后按比例添加棕色、黄色、蓝色或黑色染料,调节纸张的亮度L值。     

新闻纸、铜版纸和涂布白纸板印刷适性的对比研究

以新闻纸、铜版纸和涂布白纸板为研究对象,测试其物理性能,采用IGT印刷适性仪印刷油墨,使用x-Rite SpectroEye分光光度计测定了印刷测试条的L*、a*、b*值和实地密度,计算了油墨的色相误差、色灰度和色效率。研究表明,与铜版纸和涂布白纸板相比,新闻纸偏黄、略偏红,纸面效率低,彩色印刷时呈色范围小,油墨色相误差较大、灰度大、色效率低。为提高新闻纸的彩色印刷效果,应适当提高新闻纸的平滑度,适当降低其吸墨性,减小新闻纸色度偏黄的程度。     

彩色数字喷墨打印机色彩特性化方法研究

图像输出设备色彩特性文件描述了图像设备的色彩再现能力,是图像复制色彩管理流程中颜色转换的关键.本文通过立方体插值法实现颜色空间转换,应用最大分区法与色域裁剪法实现色域匹配,设计实现了彩色数字喷墨打印机的色彩特性化方法.在此基础上,开发了彩色数字喷墨打印机色彩特性文件生成软件.最后,从色域、中性灰再现能力及色差三个方面对生成的打印机色彩特性文件进行评价.实验结果表明,基于本文设计的彩色数字喷墨打印机色彩特性化方法生成的色彩特性文件可以满足图像复制色彩管理流程中颜色转换的精度要求.     

天然染料染色羊毛的色域拓展及颜色预测模型

天然染料色谱不全的缺陷限制了其在羊毛上的应用。为丰富天然染料染色羊毛纤维的颜色色谱,选用天然红、黄、蓝三原色染料染色羊毛织物与纤维,然后对羊毛织物的一浴法拼混染色和有色纤维的拼色进行研究,并基于Kubelka-Munk单常数理论和Stearns-Noechel模型分别对一浴法拼混染色织物和拼混有色纤维进行颜色预测。结果表明：使用一浴法拼混染色,染色后的羊毛织物在CIELAB色域空间中分布不均匀,倾向于红(+a^*),色相角(h)分布范围主要集中在0°～24°、324°～360°之间;经有色纤维拼混获得的颜色空间分布更加均匀,更倾向于黄(+b^*),色相角(h)分布范围集中在0°～50°、316°～360°区域;Kubelka-Munk模型和Stearns-Noechel模型可分别用于天然染料一浴法染色羊毛织物和羊毛有色纤维拼色的颜色预测,为进一步提高生产效率、降低配色成本提出新思路。     

铜版纸色调对印刷色彩表现性能的影响

利用Neugebauer方程从色度学的角度探讨铜版纸色调对印刷色彩表现性能的影响，包括印刷实地色度值、印刷中性灰平衡和印刷色域等关键印刷要素。结果表明：纸张色调对印刷色彩表现性能有较大影响，不同色度的纸张，其印刷色彩表现特性不同，在实际的印刷生产中，要根据纸张色调适当调整印刷工艺以达到色彩的准确复制。     

HUE ANGLE DETERMINATIONS AND STATISTICAL ANALYSIS FOR MULTIQUADRANT HUNTER L,a,b DATA

For purposes of data analysis and data interpretation, it is important to have uniform representation of hue derived from the Hunter L, a, b color space. Using the standard calculation for hue [Arc tan (b/a)], positive signed results are generated for the first quadrant [+a, +b] only. The other quadrants should be handled so that a 360° representation is accommodated and results are expressed as positive signed numbers. Second quadrant [-a, +b] and third quadrant [?a, ?b] calculations should be: hue = 180+Arc tan(b/a). Fourth quadrant [+a, ?b] calculations should be: hue = 360+ Arc tan(b/a). Furthermore when planning statistical analysis of data which transverse the IV and I quadrant, tranformations of the data will continue increasing in hue angle from 361° on up as high as appropriate. A spreadsheet macro for achieving these results can be easily derived.     

Evaluation of Venison Color by an Objective Method using CIELAB Values

A trained color panel was used to score both venison color and color acceptability for comparison with instrumental color measurements. Panel color scores were highly correlated with acceptability (r = 0.97) and could be predicted from CIE L*, a* and b* values by regression (R² (adj) = 0.84). The use of a* alone explained the greatest amount of variation R² (adj) = 0.78), and the inclusion of both L* and b* significantly improved the model. The use of hue angle and chroma either individually or in combination with L* did not provide better relationships. The use of L*, a* and b* is recommended for satisfactory prediction of panel color scores of venison with no less than three observations per sample.     

基于CIECAM02颜色空间均匀性的研究

颜色空间的均匀性是评价一个颜色空间质量好坏的一个重要方面,其均匀的程度对色差计算和色域映射的准确性有重要的影响。首先介绍CIECAM02,然后利用孟塞尔新标数据,分别从明度、彩度和色相三个方面评价CIECAM02-Jab的均匀性,评价的结果表明明度的均匀性较好,而彩度和色相的均匀性要相对差一些,需要做进一步的改进。     

RELATIONSHIP BETWEEN INSTRUMENTAL AND VISUAL COLOR IN A RAW, FRESH BEEF AND CHICKEN MODEL SYSTEM

A range of meat redness was created by mixing fresh, chilled ground chicken breast and ground beef in predetermined ratios. Samples were scored for visual redness under halogen (incandescent) and cool white fluorescent lighting. Instrumental color characteristics (L*, a*, b*, hue angle, chroma; illuminants A and F) and red color contributed by oxymyoglobin (percentage reflectance at 630 nm versus 580 nm) were determined. Correlation coefficients were determined between visual and instrumental evaluations. The a*, b*, and ΔR (630–580) were highly correlated to visual redness (halogen light: r = 0.99, -0.99, and 0.96, respectively; cool white fluorescent light: 0.98, -0.98, and 0.96, respectively). Regression analysis was conducted to develop equations to predict visual redness using instrumental color measures. In the 20% to 85% beef range, the regression curves were principally linear although the overall relationships (0–100% beef range) were cubic. Among the instrumental color parameters, a*, hue angle, and ΔR (630–580) could be used to predict visual redness for this model system.     

Performance testing and evaluation of reactive dye inks for silk digital printing北大核心CSCD

In order to explore suitable reactive inks for silk digital printing, reactive dye inks of eight brands were selected from the domestic market to evaluate their pH, Conductivity, absorption spectrum, color gamut range and their application performance including color yield, dry and wet rubbing fastness. The results showed that pH values of ink of different brands ranged from neutral and weakly acidic property, which would be helpful to reduce hydrolysis of the reactive dye and improve their stability. Reactive inks with lower conductivity could avoid salt crystallization which would cause nozzle blocking and corrosion problem. The hue of three primary colors (CMY) was stable, while that of spot color (BRO) had some differences, and the overall gamut range of these ink sets were different at different brightness levels. The application performance of the printed silk demonstrated that the increase in the stability of reactive ink would improve the color yield and color fastness of the printed fabric. © 2018 China Silk Association. All rights reserved.     

Measuring pork color: effects of bloom time, muscle, pH and relationship to instrumental parameters

To evaluate factors affecting pork color, the gluteus medius (GM), longissimus lumborumetthoracis (LT), semimembranosus (SM), biceps femoris (BF), and triceps brachii (TRI) muscles from pork carcasses of varying ultimate pHs were allowed to bloom for 30 min. L*, a*, and b* values, hue angle, chroma and visual color were determined. Color was evaluated using HunterLab (illuminants A, C, D(65) and F) and Minolta (illuminants C and D(65)) Spectrocolorimeters. LT had the highest L* value (51.31; TR=39.93) and hue angle (59.36; TR=46.94), and the lowest a* (7.52; TR=12.88) value. L* value was unaffected by bloom time; hue angle stabilized after 5 min, a* and b* values after 10 min and chroma after 20 min. Using the Minolta/illuminant D65, visual color best correlated with b* and L* values (r=-0.94 and -0.89) of LT. Using the Hunter/illuminant C, visual color correlated with L* value of LT, GM, BF and SM (r >-0.90 for each). Overall, the instrumental measure that best related to visual color was L* value.