彩色印刷图像混合半色调化关键技术研究

发布时间：2018-11-15 15:24

【摘要】：数字图像在输出前必须转换成与输出设备深度相同的图像。图像半色调化是一种将深度较高的图像转换成深度较低的图像,并且使两者在视觉上尽可能相似的技术。图像半色调化技术在涉及图像输出的很多领域中有广泛的用途,如印刷、户外广告制作、电视、电子游戏、动画、联机的图像显示和网络传输等领域,它是决定输出图像质量的关键技术。图像半色调化技术对研究输出图像的质量控制和优化、输出图像的颜色预测、针对不同输出设备的半色调化图像质量评价具有重要意义。在实际应用中,图像输出设备存在局限、图像输出设备的多元化、输出图像质量评价中主观因素给图像半色调化技术研究和应用带来了挑战。本文以彩色印刷为应用背景,以提高输出图像质量为目标,以图像半色调化及相关技术为研究内容,展开了从基于几何分割的半色调化抖动矩阵设计方法,到混合半色调化的色彩偏移问题,再到半色调化图像质量评价体系的系列深入研究。主要研究成果包括: (1)针对现有基于Delaunay三角化几何分割设计的混合半色调化抖动矩阵存在阴阳集束网点密度相差悬殊的缺陷,本文提出了通过优化几何分割减少该缺陷方法。该缺陷在实际应用中将妨碍集束网点密度的提高,而提高集束网点密度是提高输出图像质量的关键因素。本研究从欧拉公式推导出了两条关于几何分割的性质,其中关于全三角形几何分割的性质可以准确地解释造成现有研究成果中阴阳集束网点密度相差悬殊的原因,然后以全四边形几何分割的性质为依据,提出了优化几何分割的算法。实验中该算法将顶点数与子区域数的比例从优化前的0.5改进到了0.90以上。在该优化的几何分割的基础上设计混合半色调化抖动矩阵时,其阳集束网点和阴集束网点密度之比也相应地改进到了0.90以上。 (2)提出了通过扩张初始集束网点中心点集构造阴阳集束网点密度相等的混合半色调化抖动矩阵的方法。它可以在满足印刷工艺限制的条件下进一步提高混合半色调化图像中的集束网点密度,从而提高印刷质量。为了验证扩张中心点集方法的合理性,实验中将扩张前后的中心点分布转换成半色调化图像以比较它们的均匀性。除此之外,还将全四边形化几何分割的四边形与优化的几何分割中四边形的质量因子做比较。实验结果表明:扩张前后中心点分布对应的半色调化图像的峰值信噪比(PSNR)接近,而且全四边形化几何分割中四边形质量因子与优化的几何分割中四边形质量因子相比也有所改进。 (3)提出了一种用半色调化图像错位叠加仿真套印误差,并且用Yule-Nielsen Neugebauer颜色方程和彩色胶印颜色标准ISO12647计算色彩偏移量的方法。实验中将本论文研究设计的混合半色调化抖动矩阵的色彩偏移量与调幅半色调化的色彩偏移量比较后得到如下结论:用三个不同的随机数种子生成的混合半色调化抖动矩阵的色彩偏移量与调幅半色调化的色彩偏移量接近,色彩均匀性也接近。因此,用本论文方法设计的混合半色调化抖动矩阵,其色彩偏移量完全可以满足印刷工艺的要求。 (4)提出了一个统一的针对不同图像输出设备的基于非理想打印机模型的半色调化图像质量评价体系。本论文研究用数学形态学的膨涨运算(Dilate)仿真印刷工艺过程的网点扩大现象,并将膨涨运算参数与胶印网点扩大曲线拟合,加上本文提出的小网点过滤算法,建立了面向胶印工艺过程的非理想打印机模型。结合人类视觉系统(HVS)模型计算人眼感知的图像,实验检验了基于非理想打印机模型的的半色调化图像质量评价方法。本论文研究的实验表明,用该评价方法比基于理想模型的评价方法得到的结果更接近胶印生产的实际。
[Abstract]:The digital image must be converted to the same image as the output device depth before the output. Image halftone is a technique that converts a higher depth image into a lower depth image, and makes both visually similar. The image half-tone technology has a wide application in many fields involving image output, such as printing, outdoor advertisement production, television, video games, animation, on-line image display and network transmission, etc., which is the key technology to decide the quality of the output image. The image half-tone technique is of great significance to the quality control and optimization of the output image, the color prediction of the output image, and the semi-tone image quality evaluation for different output devices. in that practical application, the limitation of the image output device, the diversification of the image output device, the subjective factor in the quality evaluation of the output image are brought to the research and application of the image semi-tone technology research and application, In this paper, based on the background of color printing, this paper aims to improve the quality of the output image, and based on the half-tone and related techniques of the image, the design method of the half-tone dither matrix based on the geometric segmentation is expanded to the color shift of the mixed half-tone. In-depth analysis of the quality evaluation system of the half-tone image Research. Main research results The method comprises the following steps of: (1), aiming at the defects that the existing hybrid half-tone dither matrix based on the Delaunay triangulation geometric division design exists in the difference of the density of the positive and negative cluster dots, and the reduction of the geometric division is proposed in the paper, The defect is to improve the density of the cluster dots in the practical application, and to improve the density of the cluster dots is to improve the quality of the output image. The key factors of the study are derived from the Euler's formula, and the properties of the geometric segmentation are derived from the Euler's formula, in which the properties of the full-triangular geometric segmentation can be used to explain the causes of the difference between the density and the density of the positive and negative cluster dots in the existing research results. The optimization of the geometry is put forward based on the properties. in the experiment, the ratio of the number of vertices to the number of subareas is improved from 0. 5 before the optimization to 0. More than 90. When the hybrid half-tone dither matrix is designed on the basis of the optimized geometric segmentation, the ratio of the density of the male and female cluster outlets is also improved to 0. and (2) a mixed half-tone with the same density of the positive and negative cluster dots is constructed by expanding the center point set of the initial bundle branch point, The method of the invention can further improve the density of the cluster dot in the mixed semi-tone image under the condition that the printing process is limited, so as to improve the printing quality. in order to verify the rationality of the expansion center point set method, the center point distribution before and after expansion is converted into a half-tone image in the experiment to In addition, the quadrilateral and the optimized geometric partition of the whole-quadrilateral geometry are also divided into four. The experimental results show that the peak signal-to-noise ratio (PSNR) of the half-tone image corresponding to the distribution of the center point before and after expansion is close to that of the half-tone image, and the quadrilateral quality factor and the quadrilateral quality in the optimized geometric partition are the same. (3) A simulated overprint error with half-tone image is presented, and the Yule-Nielsen Neugebauer color equation and the color offset color standard ISO1264 are used. 7. The method of calculating the color offset. In the experiment, the color offset of the mixed half-tone dither matrix and the color shift of the amplitude-modulated half-tone are studied in this paper. The results are as follows: the color offset of the mixed half-tone dither matrix generated with three different random number seeds and the color offset of the amplitude-modulated half-tone As a result, the mixed half-tone dither matrix is designed in this paper, and its color offset is complete. the requirements of the printing process can be met. (4) a unified non-ideal printer model for different image output devices A semi-tone image quality evaluation system based on mathematical morphology is studied in this paper. In addition, the small-point filtering algorithm proposed in this paper has set up the face-oriented glue. A non-ideal printer model for the process of printing process. The human visual system (HVS) model is used to calculate the image of human eye perception, and the model based on the non-ideal printer is tested. The experimental results of this paper show that the evaluation method is more effective than the evaluation method based on the ideal model.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：TP391.41

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